Intermittent electrical fault?

[keithC70]

Today I set off and within 20 miles the lights had come on. I stopped and deleted them and scrounged a bit of cardboard and used Dave's tip.

Just back after 90 miles and no lights! Thanks Dave, brilliant tip which makes me think maybe dirty contacts on the multiplug.

Anyway stopped at the breakers on the way home and managed to get the module off (£16), in the rain and almost dark, so very pleased as I now have a spare to dismantle and re solder.

Thanks for all your helpful comments.

Keith

[DaveNP]

Glad the cardboard bodge worked. From my experience it's not the contacts in the plug that are the problem but it's where the contacts in the socket are soldered into the circuit board in the electronics unit. The plug must put a little bit of strain on the pins and vibrate as the car goes along which leads to the solder actually cracking, known as a dry solder joint, once you're into the box it's not too tricky with a good soldering iron to just touch each solder blob to make it melt and reset.
I think I've got some pics on the wife's computer which I'll try to upload soon.

[DaveNP]

Unfortunately my wife has deleted my photo's off of her computer, I really should have saved them for myself but my laptop doesn't have the software to manipulate the images hence using her desktop.
If you've got the luxury of a spare unit, first check all of the part numbers match, I've known some electronic parts which would appear to be the same but when you swap them they don't behave properly.
There's various threads/blogs/videos on the net about getting into them, I found it did end up being a bit destructive of the join as the edges of the pieces are both channels which interlock with each other all filled up with mastic. When you get to the circuit board some of them have a protective film over the back/soldered side of the board which would need stripping back. The solder joints which fail are most likely the ones for the pins for the plug socket, if you've got some good magnification you can see the cracks in the solder although like the images below a very fine crack is all that is needed to ruin the contact (it's why the cardboard bodge works as it deflects the pin enough to make contact again). Fixing the solder just needs a hot soldering iron to melt the solder then let it reset, the hotter the iron the better as it will melt the solder instantly and you can then take the iron away quickly rather than having to hold a not so hot iron on it for longer and risk heating up the board and other components too.

[keithC70]

Many thanks for your tip Dave.

I've now completed over 300 trouble free miles without any further warning lights. Hope it lasts a long time.

Also thanks for the great photo showing the cracked solder. I'll get round to soldering all the loose joints eventually!

Just need a bit of leather to sew up the rip on the seat now!

Thanks for all your input.

Keith

[keithC70]

Just to finish off the story, I continued with the cardboard for a while and it got me through the mot but finally after the cold spell I took off my asb module.

It had already been opened and sealed. I carefully examined it but could see no signs of cracks or of repair by anyone. It was part no 9467582.

So I decided to open the one I got from the breakers. It had not been opened previously and was part no 8619535. I used a hot knife to melt the plastic, very quick and easy to do and left a clean level surface to glue back together.

Again I could see no cracks and so re-sealed it and fitted it back on the car.

It's working perfectly so far, about 300 miles.

So for £16 I've extended the life of the car, which is great, so thanks for the helpful comments everyone.