How not to fix a central heating boiler - Page 1
Forum section: electronics / repair

author: chris_leyson
author_rank: Super Contributor
timestamp: January 16, 2016, 03:51:03 pm
content: So the central heating boiler has been acting up for a few weeks, what could it possibly be this time, over 16 or 17 years it's had three replacement flue extractor fans, three replacement water pumps, a couple of diverter valves, two sets central heating stop cocks, a set of manifold couplings and a repair to the PCB where the 20mm pcb mounted fuse clip had got so hot it had turned that corner of the pcb into carbon. It's cost more in spares than the damn thing cost in the first place but at least I didn't call a plumber that would be £100 call out charge each time, I thing I'm in the wrong business somtimes.OK, so next time I'm home I'll have a look, the flashing LED on the front panel says central heating sensor fault. It's either the 100C over temperature trip or the thermistor that measures the water temerature after the burner. Off comes the cover, check the wiring, check the sensors, everything seems to be OK now, strange maybe it's a loose wire I don't know I can't find anything out of order.A few days later I get a phone call, boilers on the blink again. OK, order a set of replacement sensors that's another £40 and I'll come down at the weekend and fit them. After fitting the sensors the damn thing still isn't working. There was nothing wrong with the old sensors, they checked out OK. Read the manual again, maybe it's one of the adjustment pots for setting the burner pressure or temperature, best to leave those alone, but I'll check the controller pcb just in case.It turned out that the room thermostat connector had dropped off, I should have checked thatA

author: VK5RC
author_rank: Unknown
timestamp: January 17, 2016, 09:27:26 am
content: Glad to hear someone else does that sort of thing, l remember the best part of a day getting an ancient PC to talk via usb serial port emulation to a GPIB adapter, tried all variants of flow, stop etc, turned out to be a loose connector. Lots of blue air in the lab.

author: bookaboo
author_rank: Frequent Contributor
timestamp: January 17, 2016, 11:11:56 am
content: I once lost an entire Sunday to a dodgy USB lead, had gone as far down the wrong path as to rebuild the project and borrow a friends Real Ice as I was sure mine was faulty.

author: BradC
author_rank: Super Contributor
timestamp: January 17, 2016, 11:31:26 am
content: I removed, re-sealed and replaced an entire automatic transmission to find the leak was a pinhole in the fluid cooler line where it passed through a clamp on the side of the bellhousing.

author: Ampera
author_rank: Super Contributor
timestamp: January 18, 2016, 03:23:10 am
content: At least it wasn't 100c over the limit.Normally boiler tanks have a pressure release valve. So if the pressure gets too high it sprays steam everywhere.If the temp meter for the boiler was 100c over a probably decent limit and nothing was venting, then you would have started the hole for a new extension to your home.An elevator.

author: edpalmer42
author_rank: Super Contributor
timestamp: January 18, 2016, 04:58:39 am
content: To add insult to injury, it seems like I only make a fool of myself when someone else is around. On my own, I'm a genius, when someone else is around, I'm an idiot.Ed

author: Cubdriver
author_rank: Unknown
timestamp: January 18, 2016, 05:52:33 am
content: Quote from: edpalmer42 on January 18, 2016, 04:58:39 amWell of course! Making a fool of yourself when no one is around to see is a complete waste. Fate doesn't waste effort like that - it waits till you have an audience.-Pat

author: Brumby
author_rank: Unknown
timestamp: January 18, 2016, 06:24:22 am
content: Quote from: Cubdriver on January 18, 2016, 05:52:33 amNot always.Sometimes you get away with it in the moment - but fate will catch you up down the track when a situation arises where your 'experience' will be called upon. In those moments I pray there is no-one around who fully comprehends the situation and asks "How did you know that?"

author: edpalmer42
author_rank: Super Contributor
timestamp: January 18, 2016, 07:08:47 am
content: One time I somehow managed to plug in the power connector to a floppy drive wrong. The drive did not survive! Years later, I was volunteering with a group that refurbishes computers.Him: "All I did was plug in the floppy drive and now the computer is completely dead."Me: "Check the power connector".Him: "Wow! How did you know!"Me: "just a hunch."Later, I did confess 'how I knew'.Ed

author: Nerull
author_rank: Frequent Contributor
timestamp: January 18, 2016, 12:50:13 pm
content: Quote from: TwoOfFive on January 18, 2016, 03:23:10 amDid you ever see the incident where someone "fixed" the pressure release valve on a LN2 tank by welding it shut?Quote

author: madires
author_rank: Super Contributor
timestamp: January 18, 2016, 01:52:41 pm
content: Currently I'm helping a friend to fix a broken car lifting platform which goes only up. A car mechanic was creative and swapped the push buttons for up and down, not realizing they got different contacts (opening/closing). Of course he also messed up the wires (18 wires!).Luckily no magic smoke escaped. Did I mention there's no documentation or circuit diagram?Happy reverse engineering ...

author: rrinker
author_rank: Super Contributor
timestamp: January 18, 2016, 03:58:23 pm
content: Quote from: Nerull on January 18, 2016, 12:50:13 pmNothing new there. On one of the very first steam locomotives in the US, the fireman got annoyed at the sound of the steam escaping from the safety valve, so he wired it shut. With predictable results.

author: mikerj
author_rank: Super Contributor
timestamp: January 18, 2016, 04:20:13 pm
content: Quote from: edpalmer42 on January 18, 2016, 07:08:47 amI killed a couple of 3.5" floppy drives in the same way many, many years ago. It was a pretty poor connector design to be fair and easy to get wrong if you weren't careful so I suspect we weren't the only pair of idiots to do this

author: Cubdriver
author_rank: Unknown
timestamp: January 19, 2016, 03:14:58 am
content: Quote from: rrinker on January 18, 2016, 03:58:23 pmThe Best Friend of Charleston. In hindsight he probably should have taken the hiss over the boom.-Pat

author: rrinker
author_rank: Super Contributor
timestamp: January 19, 2016, 03:29:26 am
content: Quote from: Cubdriver on January 19, 2016, 03:14:58 amding ding ding, we have a winnah.

author: Cubdriver
author_rank: Unknown
timestamp: January 19, 2016, 03:58:44 am
content: Hah. I have a book on train wrecks at home. (That's actually the title: Train Wrecks) Must be going on 40 years now; have had it since I was a kid. Things like that boiler explosion (after that they started putting a flatcar stacked with cotton bales between the engine and passenger cars), the Ashtabula Bridge disaster, telescopes and snakeheads, horrific fires in wrecks from overturned coal stoves, all that sort of stuff. Great reading material for a ten year old!Anywho, haven't opened the book in years, but the name of the locomotive came instantly to mind when I read the post. Funny the things you remember...-Pat

author: nfmax
author_rank: Super Contributor
timestamp: January 19, 2016, 07:45:50 am
content: The Internet is truly wonderful. Visithttp://www.railwaysarchive.co.uk/and spend hours browsing through the contemporary enquiry reports into 19th Century UK railway accidents of all types, some of them particularly hair-raising. Search for the Quintinshill collision (1915, not 2002) for what was probably the worst collision ever, in terms of lives lost.