Wireless Monitor for Auto Problem Diagnostic - Page 1
Forum section: electronics / general

author: EPAIII
author_rank: Super Contributor
timestamp: October 26, 2022, 07:01:05 am
content: I have an Envoy that I purchased used a few years ago. Now it has an intermittent problem with the low beam headlights. Sometimes they come on and work perfectly normal and others they will not turn on no matter what. There is no half way or dim operation. It is either completely on or fully off. The dealer wants to replace the "module" which, with the labor and whatever, will probably cost over $1K. And they will not guarantee the diagnosis. If that does not fix the problem, it is still on me. No refund. No we will take it back. No we will then fix it with no further cost to you. NOTHING in the line of a guarantee past the 30 day point and for even that I would need to show them the problem. From the intermittent nature of this problem it could easily work OK for weeks and then act up again. And I would be stuck with the full bill for all repairs even if nothing is actually fixed.I have replaced the relays, which are on the outside of the "module" but that didn't help. And I have been looking for a loose wire but have had no luck there.I may consider paying for the module IF it is really at fault. But I want positive information to that effect and the only way I can think of getting that is by driving it and waiting for a failure. Then I need to be ready to get at least one test result before I stop or turn the key off.With my background, it should be easy to come up with a circuit that can:1. Connect to a point in the headlight circuit to monitor it. A simple LED or two can easily tell if the 12 Volts or a ground is present.2. Allow me to force the headlight ON. This will be necessary since I need to be testing it while driving at night and I don't want to be stuck with no headlights.3. A second monitoring indication would be nice to monitor if at least one of the headlights was actually on. A photocell would be good for this. Or two.Now I am 78 years old and I am not eager to personally run a cable from the engine compartment to the inside of the vehicle. I have crawled under my last vehicle - or so I hope. So I have been trying to get someone to do that for me. Sounds simple. But neither the dealer nor my normal mechanic is willing to do this. They cite liability if something happens due to a non-OEM modification. I tried other shops and got more refusals.So now I am thinking about a wireless troubleshooting device. And I am asking for some ideas on how something might be designed. I assume there is a pretty solid metal wall between the engine and the passenger compartment so what type of system might work? Perhaps something with a pair of small antennae on the windshield? But frequency and power levels? And it would need to be two way to allow both monitoring and control.Any ideas or suggestions would be appreciated. Or just tell me if I am crazy.

author: Benta
author_rank: Super Contributor
timestamp: October 26, 2022, 06:28:08 pm
content: Before going to a major project, using the OBD-II interface for diagnosis could be an idea.Lots of OBD-II to Bluetooth modules around plus associated apps for phone/tablet/laptop display/event recording.

author: EPAIII
author_rank: Super Contributor
timestamp: October 27, 2022, 06:38:53 am
content: Neither the dealer not any of the shops that I talked to about this problem. I am sure they have OBD-II readers.Just how would that device know if the headlights are actually on or off? Are there photocell sensors on them?And if I am driving around at night and the headlights go off, can that OBD-II reader absolutely turn them ON? Somehow I doubt it.I am sure it talks to some on-board computer and can only report on what that computer knows. And then, that computer probably controls the lights in the first place. So if it is turning them on but they are not on, how would it know. Too much reliance on the automation. This needs real troubleshooting.You mentioned bluetooth so I guess I will start with that.Quote from: Benta on October 26, 2022, 06:28:08 pm

author: Benta
author_rank: Super Contributor
timestamp: October 27, 2022, 10:16:51 am
content: No, no photosensors.But they normally monitor current draw in the bulb to detect for a broken filament.

author: bw2341
author_rank: Regular Contributor
timestamp: October 30, 2022, 06:18:12 pm
content: I think it would be better to try and find the actual fault yourself.Any kind of modifications that can detect and control the lights independently would require cutting into unbroken and watertight wires, creating the risk of new failures in the future.I follow the South Main Auto youtube channel. Eric O. is very good at finding electrical faults.https://www.youtube.com/c/SouthMainAutoRepairAvocaHis technique is to use the wiring diagram to examine and test the faulty circuit from one end to the other. The wiring diagram will tell you which connectors and grounding points affect your lights. He even has a video on an Envoy with faulty low beams:In this case, it was a faulty relay. In other electrical fault videos he would continue by following the control wire back to the Body Control Module. For example, you can test if the control wire signal is present and steady at the relay socket. A multimeter alone could be misleading because it does not load the circuit. Eric O. would use a low wattage automotive bulb on jumper wires instead. That would prove that the control wire can send enough current to drive the relay. If there is an intermittent break in the connection, the bulb may flicker. By using the same technique on every connector, you can prove that each section of the wiring is working.Be very careful probing automotive connectors. They are delicate since they are made as cheaply as possible. A multimeter probe would probably ream them open permanently. The recommended automotive probe pin is the T pin from the sewing or office supply store. The T-shaped handle allows for a reliable connection with an alligator clip.In most of SMA's videos, the fault is usually a corroded or broken wire or connector. Try and follow the wire as close as you can and look for abrasion in the loom or tape covering the wiring harness. Often the fault is in a shoddy previous repair. Look carefully at every connector for signs of corrosion.Unfortunately, a lightly intermittent fault is most difficult fault to repair. Even South Main Auto refuses to work on intermittent faults.

author: jmelson
author_rank: Super Contributor
timestamp: November 01, 2022, 08:33:20 pm
content: Does this car have a headlight switch on a stalk from the steering column? Those switches often fail from motion of the turn signal.So, the issue could be in the switch or wiring to the turn signal.Jon