Weird electrical problem

[cthulhu]

Hi Guys,

I've got a 406 Turbo Exec that just last night developed a weird electrical problem. It's got the following symptoms:

- Remote central locking has stopped working (the key's LED still lights, so it's not flat)
- Accessories circuit always seems to be on

So even with the ignition key removed and the doors locked the radio stays on, anything plugged into the cig lighter circuit stays on, and so do interior lights, and the battery tell-tale in the instrument cluster is always on.

I've eyeballed all the fuses in the cabin and seem ok. Fuse 1 is set to its first position so the cig lighter circuit should be off when the ignition is.

Basically I parked the car last night and remote-locked it, then came back an hour later and found the radio was still on and I needed the key in the lock to open the doors.. had to disable the alarm manually.

Any ideas??

[jasper5]

Look under the drivers carpet and side panels for dampness, check all the electrical connections, clean them and spray WD40 all over them.

Corrosion in these connections causes all sorts of weird problems.

[cthulhu]

Will do, thanks. It's a nice warm day today (so far anyway), so if it is dampness it might clear itself up before I get a chance. Fingers crossed.. otherwise I can just see the main dealer charging my monthly salary to troubleshoot this one, so I'd rather find a fix.

[teamster1975]

Possibly the ignition barrel? You could test that by unplugging the barrel to see if everything goes off.

[cthulhu]

Possibly the ignition barrel? You could test that by unplugging the barrel to see if everything goes off.

Where's the plug for that? Is it just under the steering column, or is it tucked away somewhere unexpected?

[teamster1975]

Take the bottom shroud off and you should be able to get to the back of the barrel; I've never had to do it myself.
It'll help if you release the steering column adjuster so that you can pull the wheel right out.

[cthulhu]

There doesn't seem to be any dampness anywhere, and I pulled the three plugs that seem to be connected to the ignition switch (I haven't removed the lower steering wheel shroud yet, but going by the haynes manual these are the right plugs.. will remove the shroud and confirm), and it made no difference. Hm.

There must be a short somewhere, I figure, but the question is where. I've been scouring the Haynes manual's generic wiring diagrams, and it does look like the remote central locking receiver gets a signal when the ignition is "on" or in the accessories position, which would explain why the remote locking doesn't respond, so I'm going to try and back track that to see where there might be a short to put a voltage on that line when the ignition is off. Any pointers appreciated.

[cthulhu]

It turned out that the relay responsible for switching the rear windscreen heater circuit was stuck on. I've just pulled it out for now while I source a replacement.

[steve_earwig]

Nice one! Umm, how did you find it?

[cthulhu]

I discussed the problem with a friend of mine who's a bit more clued up on electronics than I am. First thing he said was "It sounds like a busted relay". Since there are only about 5 of them in the car, we just pulled each one in turn until the problem went away.

The dealer wants £39 for a new one! Not likely.

[teamster1975]

Job well done mate! Trip to the breakers I reckon

[steve_earwig]

Nice one! I hope you bought him a pint