Automotive relay help - Page 1
Forum section: electronics / projects

author: dbert
author_rank: Contributor
timestamp: October 17, 2022, 04:17:52 am
content: Hello Brain Trust, newbie here. I have only enough electronics knowledge to cause a lot of damage, so I've come here to see if I can find an answer to a question about the function of an automotive relay I'm having trouble with.The relay in question came out of a 1989 Ferrari 328. It is not functioning correctly, and it was made 33 years ago in VERY small quantities. I have several parts suppliers looking around the world for a replacement, but no one is hopeful that once can be found. So I'm forced to devise an alternative. This relay drives a brake pressure pump and is critical to the operation of the braking system.Most automotive relays are very simple. A typical one is supplied with battery power on a high current circuit. Inside the relay is a coil that is energized by an incoming trigger voltage (usually switched). The coil's magnetic field causes a high current switch to close, which connects the battery power to whatever device is controlled by the relay, like a motor or a lamp.Usually the relay coil only has a resistor across it, but the one I'm dealing with has a PCB inside the relay with a PNP transistor and 5 resistors. It looks like this:I know this isn't much to go on, but I'm trying to understand the purpose of the transistor in this thing. If it matters, it's a B327-25. All that the relay needs to do is close the contact and connect pin 30 to pin 87 when a trigger voltage (12V) comes in on pin 85 (from the car's ignition switch). As you can see, the emitter is connected to the coil and the collector connects to battery supplied power.Before I try using a generic $5 relay and possibly damaging something else in the car, can anyone take a guess at what that transistor's purpose is?Hope I posted in the right place. None of the Ferrari techs I've talked to have an answer. TIA.

author: dbert
author_rank: Contributor
timestamp: October 17, 2022, 04:28:42 am
content: I forgot to mention...the part of the relay that has failed is the coil. It no longer switches in response to the trigger input. If I press it closed with my finger, I get continuity between 30 and 87 as I should.

author: floobydust
author_rank: Super Contributor
timestamp: October 17, 2022, 04:46:58 am
content: The PNP transistor is likelyBC327-25CBE pinout.That schematic is wrong and the 5 extra parts are important to know. I think the glass diode with 3 yellow stripes is a zener diode and it would take a test to see what its value is or perhaps people here know the markings.I can't see the three parts stashed under the relay coil. A black diode, a resistor and something else.Wild guess is this relay activates when a control voltage is at a certain level or lower, and it requires very low control current to activate, as if from a small switch contacts.Sometimes with an open relay coil you can do surgery as the break is likely at the winding's end connection points. I would remove the relay from the pc board to find the open connection point.

author: geggi1
author_rank: Frequent Contributor
timestamp: October 17, 2022, 04:49:13 am
content: have you tried to measure the resistancen through the coil?

author: Haenk
author_rank: Super Contributor
timestamp: October 17, 2022, 09:38:18 am
content: I assume this is just to reduce the load on the ignition switch to a minimum.Maybe a solid state relay DC/DC would be a great alternative.

author: BradC
author_rank: Super Contributor
timestamp: October 17, 2022, 01:41:24 pm
content: Quote from: dbert on October 17, 2022, 04:28:42 amHave you actually tested the coil? A failure of the transistor would exhibit the same symptom.

author: PaulAm
author_rank: Frequent Contributor
timestamp: October 17, 2022, 01:54:22 pm
content: You should draw out the circuit or at least give us a couple of better pictures so it becomes obvious. I agree that it is quite possible the transistor is at fault and is more likely than the relay coil burning out.My guess is this was used to use a very low current from the driving module. Was that an ABS system in 89? I would strongly suspect the control signal does not come directly from the ignition switch. Not even Ferarri would do that. Since it controls the brake pressure pump, it probably comes from the brake control module.What you do not want to do is replace that with a normal relay without a full understanding of why they used that design. In any event, that should be repairable or a replacement can be made.

author: dbert
author_rank: Contributor
timestamp: October 17, 2022, 05:21:00 pm
content: Quote from: floobydust on October 17, 2022, 04:46:58 amUnfortunately, the only schematic available is what is shown in the car's wiring diagram. I just drew it out because the wiring diagram is fuzzy. I've taken some more pictures that hopefully will be helpful. I can't tell what the resistor values are under the coil. I'd have to remove the coil from the board and I'd rather not do that unless necessary.Quote from: geggi1 on October 17, 2022, 04:49:13 amI did, but I'm not certain I did it the right way. I did it by putting my test leads on the 85 and 86 pins of the relay with no voltage present on any pin, and it read something in the 20M-ohm range. I would have expected something like 100 ohms.Quote from: Haenk on October 17, 2022, 09:38:18 amYou may on to something. See my note at the end of this post regarding voltage spikes and diode protection in relays.Quote from: PaulAm on October 17, 2022, 01:54:22 pmWell, you'd be surprised what Italian engineers in the 80's would do. Indeed, the control voltage comes directly from the ignition switch to this relay when the key is in the "run" position. It's a continuous wire from the switch to the relay socket 85. Voltage is interrupted by the switch during engine cranking. This is supposed to prevent the pump (yes, it's an ABS system) from running when the starter is engaged to allow more current to the starter.You're right, I don't want to just try another relay without knowing what I'm doing. Being an old Ferrari, parts are scarce and ridiculously expensive and I don't want to damage anything. A replacement (used) ignition switch, for instance is $2k plus another 500 or so for professional installation.I removed the transistor and tested it. I'm getting the following diode voltage drops:left leg - 974right leg - 977when I reverse the test leads, I get nothing on either leg with respect to the base, so I assume that's normal. Are those numbers too high? The Youtube videos I've seen say that something in the .600-.700 range should be expected.Now then...about an hour ago someone on another board pointed me to this link -https://www.truckelectrics.com/blogs/news/automotive-relay-guide-what-is-a-relayI draw your attention to this portion:"Some automotive relays are designed with diodes or resistors built in. These devices help suppress coil voltage spikes and protect the electronic circuit.DIODE RELAY PROTECTION:When the voltage is removed and a relay is de-energized the magnetic field collapses. This can result in a voltage surge in the opposite direction. These low current surges can have significantly high voltages, often up to 100 volts. To prevent the damage of sensitive upstream electronic circuitry a diode can be installed across the coil. The diode absorbs and dissipates the momentary voltage spike and protects upstream damage. "So now I'm wondering if the transistor is just there to provide the same protection to the ignition switch that a diode would (but then why not just use a diode?) There IS a diode on the board as floobydust noticed.Pictures to come in my next post.

author: dbert
author_rank: Contributor
timestamp: October 17, 2022, 05:40:47 pm
content: Here are more pics. Does the symbol circled in red in the picture of the relay's outer case mean anything to you? It may just be a company logo but I think I've seen it before somewhere.

author: dbert
author_rank: Contributor
timestamp: October 17, 2022, 05:42:57 pm
content: More pics

author: dbert
author_rank: Contributor
timestamp: October 17, 2022, 05:45:57 pm
content: More pics

author: dbert
author_rank: Contributor
timestamp: October 17, 2022, 05:46:39 pm
content: Last one.

author: bdunham7
author_rank: Super Contributor
timestamp: October 17, 2022, 06:06:54 pm
content: What ABS system is used in this model? I'm thinking that the relay is not driven directly by the ignition switch, but rather is actuated by the pressure switch on the brake accumulator. The purpose of a transistorized relay would be to reduce the current across the contacts of that switch. It is possible that it is driven by the ABS module, but if that system is one of the ones I'm familiar with, they need the pump to function even if the ABS system fails entirely as the pump and accumulator are required for even normal braking. Does that all seem right or is there a vacuum booster?Edit: I looked it up, apparently it is Teves Mk 2, same as Jaguars, TCxMaserati and some other models of that era with early ABS systems. Every implementation has the possibility to be a bit different, but I think that relay is driven directly by the pressure switch as I said. You aren't measuring the coil properly, you need to figure out which solder pads on your board correspond with the coil wires and I can't see that in your photos.QuoteIf that is true, then the control circuit is likely on the ground side, which is a fairly common way of doing it.

author: floobydust
author_rank: Super Contributor
timestamp: October 17, 2022, 06:22:53 pm
content: It's easy to conquer this relay design, I can draw a schematic for it later this aft.The complexity is the two glass diodes with yellow stripes, I think they are zeners.It might actually have an analog signal coming in for pressure and the relay switches the pump on and off based on that. So the relay is on when pressure is low.edit: Teves Mk 2 appears to be purely mechanical pressure switches

author: strawberry
author_rank: Super Contributor
timestamp: October 17, 2022, 06:23:34 pm
content: relay circuitpull control input to 12V to activate relaydiode voltage drop on silicon BJT must be 0.6..0.7V but some weird multimeters that share ohms and diode might be exceptionyou think it is hard, try finding intermittent fault between 100 transistors and 100 resistors and no schematics at all

author: floobydust
author_rank: Super Contributor
timestamp: October 17, 2022, 06:28:10 pm
content: It's PNP and three diodes

author: strawberry
author_rank: Super Contributor
timestamp: October 17, 2022, 07:03:04 pm
content: fixed

author: dbert
author_rank: Contributor
timestamp: October 17, 2022, 08:28:41 pm
content: Quote from: bdunham7 on October 17, 2022, 06:06:54 pmI'm impressed! I wasn't expecting anyone here to know about ABS or other automotive systems. What you wrote is mostly correct. Yes the 1989 328, which is the last year it was produced (a total of about 1200 worldwide), was the only year that had ABS. And, this Italian relay we're talking about was ONLY used on this model, so you can understand how scarce it is.I have to confess that I fibbed a bit in my first post. This relay doesn't power the brake fluid pump directly. Instead, it feeds power to another relay, which in turn feeds power to the actual pump relay. Ferrari calls this first relay the "ABS Control Relay". Electrically, everything else is downstream from it.I'm attaching the complete ABS system wiring diagram, which includes all the relays, the pump, the mechanical pressure switch, the ABS ECU, the battery and the ignition switch. In Ferrari's implementation of Teves Mk 2, The ABS system and regular braking system share most of the components. In the case of ABS system failure (wheel speed sensor or even the brain itself), the pump, accumulator and pressure switch still maintain boost pressure to the regular braking system. Sadly, in the case any of the relays go bad, both systems are broken. Yep, this model doesn't use vacuum boost. Just the ABS pump.In addition to the wiring diagram, I've attached a spreadsheet with a summary of what I've learned from studying the wiring diagram and poking around with a test light. Maybe it will save you some time.

author: floobydust
author_rank: Super Contributor
timestamp: October 18, 2022, 12:47:04 am
content: Uh, I followed the Ferrari wiring diagram and find my head hurts so I put it on one page. Sorta figured it out.Relay 75 "ABS system control relay" fed from battery (with no fuse) yet control connects to the ignition/anti-theft switch. No idea what "R, 30, P, 15, 50" mean wrt to the ignition switch 88.Relay 182 "Control relay for the ABS system during cranking" connects to the ABS system module. So I think the manual has flipped the descriptions?Note this relay defaults to always on (for safety) and the control line shuts it OFF when +12V power is applied to 85.So on a workbench connecting 12V power across 30(+) and 86(-) the relay should always clank and pull in. Then connecting (+) power to 85 should make the coil release. The extra transistor and all the drama is to invert the relay's operation.OP, the 30/51 and maybe 86 terminal at the PC board looks like a cracked/fractured solder joint in the pictures. You can use a magnifier and look at it while wiggling the terminal. It's a very common failure in automotive modules. When re-doing solder joints, don't wreck it with too much heat - only need a couple seconds max. and add a bit of fresh solder.Can you give us any markings on the black diode, right now it's the only puzzle. Like 1N5xxx etc.Quote from: strawberry on October 17, 2022, 07:03:04 pmNot quite, the oddball black diode is not across the coil and there is an orange+red stripe on the resistor so likely a 3k3. I'll post what I drew in a bit, it's still not making sense though.

author: PaulAm
author_rank: Frequent Contributor
timestamp: October 18, 2022, 02:15:46 am
content: You should be glad it's not a Teves Mk3

author: floobydust
author_rank: Super Contributor
timestamp: October 18, 2022, 04:15:55 am
content: This is what I think is the relay module's schematic. Ferrari 62567200 Control Relay for ABS system, Italamec 493.The choice of diodes seems weird, three different types it appears. My concern is the battery (30) and control input (85) can have different voltages due to voltage drops in the car's wiring so it should tolerate that and I expected a (glass) zener. That diode has three yellow stripes and a grey one which is not the cathode?edit: updated schematic with ref. designators

author: bdunham7
author_rank: Super Contributor
timestamp: October 18, 2022, 04:39:05 am
content: OK, so I've uncrossed my eyes and followed the diagram around a bit, so a few questions. I also looked at your notes and they look right as far as I can tell at a quick glance.What is the part called out as '181' ?What are the exact symptoms observed with the car? Are you actually seeing the +12V on pin 85 of relay 75e when cranking? If you jump pins 30 and 87 does the ABS system then function normally?

author: dbert
author_rank: Contributor
timestamp: October 18, 2022, 05:07:41 am
content: Quote from: floobydust on October 18, 2022, 12:47:04 amThey're the male spade terminals on the back of the ignition switch.30 - constant hot from battery15 - accessories, hot when key in run position50 - connected to the starter, hot when key in start positionP - not used in the 1989 model yearR - supplies the ABS system, hot with key in run position onlyQuote from: floobydust on October 18, 2022, 12:47:04 amI'm confused by this. Are you talking about the relay I'm having trouble with, 75e? Are you saying that this thing is supposed to have the contact normally closed, and opens up when it receives voltage from the ignition switch on 85? That would seem backward to me. It would mean power is supplied downstream only when the key is off, right?

author: dbert
author_rank: Contributor
timestamp: October 18, 2022, 05:09:07 am
content: I'll reflow the joints. I also have some new transistors arriving in another day or two so I'll pop one in when I can and see if it works again.By the way, thanks for combining the two halves of the diagram. I'm curious how you did that while also making the whole thing a little less fuzzy. That helps a lot!

author: dbert
author_rank: Contributor
timestamp: October 18, 2022, 05:12:24 am
content: Quote from: PaulAm on October 18, 2022, 02:15:46 amAt the moment I'm kind of wishing it didn't even have Mk 2!

author: DBecker
author_rank: Frequent Contributor
timestamp: October 18, 2022, 05:17:07 am
content: What are the color bands on that diode?Is it a 1N4102 8.7V 1/2 watt zener? That would make sense for the circuit.I initially thought that it was the same as the ABS relay used by BMW in that era, but it does appear to have a different purpose.

author: dbert
author_rank: Contributor
timestamp: October 18, 2022, 05:35:31 am
content: Quote from: bdunham7 on October 18, 2022, 04:39:05 am181 is the ABS warning light on the dash. It lights up in case of failure somewhere in the ABS system.The +12V on pin 85 is present only when the key is turned to the "run" position. This is not during cranking, but when all the dash lights and radio come on. Then when you turn the key to crank the engine (start position), the voltage is NOT present. When the engine starts and you release the key, it goes back to +12V.I haven't tried jumping 30 to 87, but it's crossed my mind. I could be convinced to try it.Here are the symptoms:When I fire up the car and start driving, everything seems normal. No warning lights, and braking is normal. After several applications of the brake pedal, the hydraulic pressure drops below the minimum level. At that point the "brake failure warning light" on the dash lights up. Note this is not the ABS warning light, but the regular brake system warning light. After about a dozen more brake applications, hydraulic pressure is so low that it suddenly becomes extremely difficult to stop the car. Dangerously difficult. Undriveable.Here's the weird thing. If I stop the car on the side of the road and turn it off, as soon as I turn the key off, the pump turns on and pressurizes the system again. Obviously this is improper operation. The pump should not be running with the car off. It is supposed to run periodically while driving in order to maintain pressure in the system. So it runs when the car is off, and doesn't run when the car is on. This to me can mean only an electrical control issue. Mechanically the pump and the low pressure switch are doing their jobs.Now, it is entirely possible that one of the downstream relays is also malfunctioning, but before I go there I need to fix the problem with this relay first I think. All of the trouble started about a month ago, and my investigation started by pulling this control system relay to test it.

author: dbert
author_rank: Contributor
timestamp: October 18, 2022, 05:53:31 am
content: Quote from: DBecker on October 18, 2022, 05:17:07 amYou mean the one hiding underneath the coil? I can hardly see anything under there.

author: strawberry
author_rank: Super Contributor
timestamp: October 18, 2022, 07:34:30 am
content: with zener diode you can speed up relay (eevblog have some video about it) but I doubt that 1ms will do much hereabout DO-35 diode. old style color bands. small signal switching diode 1N4448 equivalent to 1N4148sometimes single band 1N4448 (yellow) and 1N4148 (black)1N4448 5uA leakage1N4148 50uA leakage

author: DBecker
author_rank: Frequent Contributor
timestamp: October 18, 2022, 02:06:27 pm
content: Quote from: dbert on October 18, 2022, 05:53:31 amPerhaps I'm missing a reason for the confusion. This appears to be a simple low and reverse voltage lockout relay as was typical for ABS units of the era.The three diodes are a glass 1N4102 8.7V zener for low voltage drop-out, a glass small signal blocking diode (probably 1N4148) for reverse voltage lockout, and a larger epoxy 1N400x type for the coil kick-back.Measure the resistance of the coil directly on the leads at circuit board, not adjacent on the traces, to verify that it has actually failed. My guess is that there is just a cracked solder joint from heat, vibration and age.

author: bdunham7
author_rank: Super Contributor
timestamp: October 18, 2022, 02:29:33 pm
content: Quote from: dbert on October 18, 2022, 05:35:31 amThat would indicate that the operation of the relay is not reversed as suggested earlier, but rather that it operates just like any other relay. With, of course, the usual disclaimer "unless something weird is going on". That would leave me baffled as to why they used a transistor pre-relay since the coil current would not be an issue for the ignition switch. Before pulling the relay, did you confirm its operation directly with a meter or test light?I'll look again to see if there's anything that would be likely to cause your 'reverse' operation. As for the pump running with the car off, I'm not entirely sure some of these didn't do that by design, but unless I missed something in the wiring diagram, your example shouldn't. A long time ago I made a tester for these Bosch-pattern relays so that you could see what all 4 legs were doing (hot, grounded, open) at one time with red/green LEDs. I'll try and dig it up. Where are you located b/t/w?I don't see a problem jumping 30 to 87, nor do I see a problemtemporarilyswapping in a more normal Bosch relay for 75e. It does bother me that there appears to be no fuse in the circuit feeding 75e. How large are the wires going to it?

author: DBecker
author_rank: Frequent Contributor
timestamp: October 18, 2022, 03:04:13 pm
content: Quote from: bdunham7 on October 18, 2022, 02:29:33 pmThe transistor amplifier is needed because of the zener diode used for brown-out protection. The relay can use a small, 1/2 watt zener and a small signal diode while using a common 12V coil. They made the module self-contained and packaged like a standard relay for easy replacement.The low and reverse voltage relay powered and protected the expensive ABS control module and sometime pump motor. They could operate on full battery voltage, without a series diode. The ABS module probably has a shunt diode for transient protection, but would immediately burn out if a battery was installed backwards or a jump start went bad.The BMW equivalent had a fuse wire and reverse diode inside the protection relay case. It was common for the fuse to burn "for no reason", along with plenty of times when it blew for an obvious/admitted reason.

author: dbert
author_rank: Contributor
timestamp: October 18, 2022, 05:44:53 pm
content: Quote from: bdunham7 on October 18, 2022, 02:29:33 pmI'm in Castle Rock, CO just south of Denver.I'll put a jumper in there to see what happens. Most of the wire sizes are indicated on the wiring diagram, shown in cross-sectional area. For instance, the ground wire connected to 86 is shown as 2.5 N, which means a black wire (Nero in Italian) that is 2.5 mm². When there is no wire size indicated, it means 0.5 mm² by default.The equivalent AWG sizes are:85 - 24 awg86 - 10 awg87 - 24 awg30 - 24 awgMy transistors from Digikey are stuck in a postal service loop and doesn't look I'll get them for a couple more days. When I do, I'll pop one in and re-flow all the solder joints. Then I'll measure coil resistance.

author: floobydust
author_rank: Super Contributor
timestamp: October 18, 2022, 06:00:12 pm
content: Quote from: dbert on October 18, 2022, 05:07:41 amYes, I'm confused too. Looking at your 75e relay pictures the transistor (thus the coil) are normally on. Control terminal 85 must be at +12V for the transistor (=relay) to turn off. But the relay is powered from the vehicle battery, which means 85 must be up all the time when the key is off. Keeping 12V at terminal 85 gives a small parasite drain of 4.4mAThe ignition switch R terminal (to 75e control) looks to be hot in key off? The pic shows the black wiper conducting nothing to R when the key is on, which fits my theory.I thought Ferrari might be a bit sinister and disable the ABS if the anti-theft is activated lol, no brakes for you! Although I have driven muscle cars through brake failures and jammed throttles, quite the hair raiser.Did you do anything to the ignition switch as far as replacements etc. ?Quote from: dbert on October 18, 2022, 05:09:07 amIt was too hard to read the wiring diagram split in two. From the original scans I imported those two pages and joined as one page, and increased the black level/contrast. Not an expert but useGIMPsometimes difficult to learn and use, but it's free and powerful.

author: dbert
author_rank: Contributor
timestamp: October 18, 2022, 06:23:10 pm
content: Nope, terminal R on the ignition switch is hot only when the key is "on", and turns off during engine start.I will also mention that I've been in touch with other owners of the 89 328, and they all say that their brake pump only runs after they turn the ignition on. I wish I could coax them to pull their relays and test the function, but they're all aware of my problem and are scared to touch it.On the ignition switch drawing, that rectangular switch is the switch that activates a warning buzzer to let you know that you left the key in the ignition when the door is open. It has no other function.

author: floobydust
author_rank: Super Contributor
timestamp: October 18, 2022, 06:49:40 pm
content: This is good, there is a mistake somewhereThe board's diodes are not making sense, it sure looks like one is installed backwards.D1 (black) diode could not be a zener as that would blow the transistor in reverse-current (no base resistor).D2 as a zener would require its cathode connected to the base.D3 (across coil) has the band going to ground...edit: only makes sense if the fat yellow band is the cathode (not the gray band) and they are not zeners.

author: floobydust
author_rank: Super Contributor
timestamp: October 18, 2022, 07:12:03 pm
content: Quote from: dbert on October 18, 2022, 06:23:10 pmAny chance the Italamec 493 relay is the wrong one for that position 75e? From the pics and the module's design, it's working as it should - backwards. From your notes, 75e pin 85 gets power during engine run (relay off) and interrupted (relay on) during cranking or key off. That's the opposite isn't it? I kind of suspect a factory documentation error or modification TBH.I would ask other 328 owners for a picture of that place on the relay panel to see if a type 493 is actually there.

author: dbert
author_rank: Contributor
timestamp: October 19, 2022, 04:42:17 pm
content: It's definitely the correct relay for that spot. Here is the page for it at one of the big parts suppliers -https://ferrparts.com/parts/Ferrari/62567200Ferrari documentation of the era is known to have numerous errors. I know of a few places in the wiring diagrams that are not correct. Ferrari was a tiny niche manufacturer in the 80's and they weren't very meticulous about documentation. They often made changes "on the fly" due to occasional parts shortages, substituting whatever they had on the shelf at the moment, so it isn't uncommon to see differences in one car vs the next one on the assembly line. For all we know they may have used this particular relay just because they had a box full of them and the regular relay was out of stock on that particular day of the week, and Luigi said "well this box of relays over here ought to work in this application, let's just use them." Porsche did the same thing.But if this relay issupposedto work backwards (normally closed, opens on input), then it makes absolutely no sense. According to the wiring diagrams and the connections between the relays, it would mean that the pump can run ONLY when the engine is off or during cranking. That is not how it is supposed to work and opposite to how the other 89 cars are working.My transistors are being delivered today so I can install one later and reflow the joints and see what we get. I'm also going to try a jumper in that position. I'm expecting that with the jumper the pump should run anytime the pressure switch calls for it, regardless of key position. I'll report back later with my results.

author: dbert
author_rank: Contributor
timestamp: October 19, 2022, 07:46:35 pm
content: Well, I'm happy to report that the jumpering (jumping?) of 30 to 87 caused the pump to run whenever the pressure switch told it to. So, I think that confirms that the relay in that 75e position needs to work like a typical relay, not backwards.And I'm sad to report that my short drive began with a rear tire sidewall blowout. Sounded like an explosion. I had to order a new tire and will take a week to get it. I was going to try a panic stop to see if the ABS kicked in, but I didn't get that far.I ordered some new relays, with flyback diodes in them. Two normally open and two normally closed (just in case). At $2.50 a pop, why not.

author: dbert
author_rank: Contributor
timestamp: October 19, 2022, 07:49:00 pm
content: Oh, and did you guys notice the solder bridge? I haven't touched any solder connections yet. I think that bridge is to a mounting post for the coil assembly that isn't supposed to be part of the circuit.

author: floobydust
author_rank: Super Contributor
timestamp: October 19, 2022, 08:40:26 pm
content: Are the original relay contacts N.C. or N.O. ? I did not see the a pic of the contacts.

author: jonpaul
author_rank: Super Contributor
timestamp: October 19, 2022, 09:08:34 pm
content: check for corrosion on connectors, cold PCB to relay solder joints, relay coil winding broken at terminals or PCB pinsjon

author: dbert
author_rank: Contributor
timestamp: October 19, 2022, 09:40:44 pm
content: Quote from: floobydust on October 19, 2022, 08:40:26 pmAt the moment, the contact is open so I assume it always was. I have to push it with my finger to close it. And after installing the new transistor and re-flowing the whole board, there is still no action from energizing the coil. Resistance across the coil is on the order of 11k ohms. I can get continuity between 30 and 87 only by pushing the contact closed.

author: bdunham7
author_rank: Super Contributor
timestamp: October 19, 2022, 09:59:55 pm
content: Quote from: dbert on October 19, 2022, 09:40:44 pm11K is way too high for that type of design, it is probably open and you are measuring some leakage thru your other components. A new, standard N.O. relay will probably fix all this (albeit without the low voltage protection function). I have no idea why your pump would run with the ignition OFF.

author: dbert
author_rank: Contributor
timestamp: October 19, 2022, 10:14:03 pm
content: Quote from: bdunham7 on October 19, 2022, 09:59:55 pmNor do I, but I'm ready to shrug my shoulders and move on. I'll let you guys know how the new relay works. Here's the one I bought:https://www.digikey.com/en/products/detail/cit-relay-and-switch/A21ASQ12VDC1-6D/12503356It does have a diode across the coil for circuit protection.

author: dbert
author_rank: Contributor
timestamp: October 23, 2022, 08:17:25 pm
content: Hi all, I finally got the new relay in and all is working as it should again.Big thanks to all of you who contributed! Much appreciated!

author: floobydust
author_rank: Super Contributor
timestamp: October 25, 2022, 05:02:17 pm
content: So the transistor stuff is gone? It's strange that something was inverting things.Also, the relay inside of the old module is a standard form factor, so it was possible to replace.

author: dbert
author_rank: Contributor
timestamp: October 25, 2022, 07:36:08 pm
content: Yep, the new relay only has a single diode across the coil, no other stuff in the box. I had to swap the 85/86 female spades in the relay sockets to respect the diode's polarity (cuz they were originally backward from standard), but the pump is coming on when it should, and not when it shouldn't. All fixed now!

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: October 26, 2022, 11:14:05 am
content: Good, the origainal relay looks like a european open-frame relay PCB mountused by most european car manufactures.Jeff