Intermittent fault on 4 electrical components

[ecsk]

I posted a question in general chat section about my problem on a M28B25 E30 convertible.
viewtopic.php?f=1&t=280940

Suddenly 4 electrical component stopped working, the four component that stopped working are turn indicator light, horn, brake light, wiper. They are controlled by the 4 adjacent fuses (4, 5, 6, 7), tapping the fuse box a few time can make them work again. I have swapped fuse and make sure they plug in securely.

I'm running out of idea, any help/opinion will be appreciated.

[Brianmoooore]

Fuses 4, 5 and 6, and 7, via a relay, are all fed with power by a multi pin plug underneath the deck of the fusebox.
The pins of this plug are in a line, and the one feeding these fuses is at the end, with a couple of unused pin spaces next to it. Chances are that the plug is partly off, with that end not connecting. This will because someone has had the deck of the fusebox off at some point, and not taken care to ensure the plug is fully seated when they replaced it.

[davidt]

This is what you will find when you take it apart .

S1035374.JPG

[Brianmoooore]

This is what you will find when you take it apart .
S1035374.JPG

And I predict you will find the purple wire end of the plug nearly off.

[ecsk]

Thanks guys. I did try test current in the thick purple wire under glove box, as soon as I poke it with a test light. everything suddenly work.
Unfortunately to fix it I believe the fuse box must be out isn't it ??

[ecsk]

Searched this forum about 'fuse box removal'. I hope I can cut some cable ties under the glovebox area and move the fuse box up a bit to access to that plug.

[davidt]

Disconnect battery, remove the two cross head screws then gently lift lift the top half of fuse box. this will give you enough room to push the plug in.

S1035369.JPG

[ecsk]

Thanks Davidt. I pull it apart as you mentioned. That plug is actually not loose, I slide my finger to push it as much as I can anyway, I didn't feel any room to push in more.
They are working at the moment, if it play up again. Would it be crack solder join in the circuit board ?

[Brianmoooore]

Crack in the circuit board, around the pin, isn't impossible, but there's another multi pin plug and socket that the wire runs through, which should be clipped to the steering column, about half way down.

[ecsk]

I'll try to look for that, however If problem is with plug near steering column, that does not explain why tapping the fuse box can make them working

[Brianmoooore]

Just giving the full range of options. I still reckon it was the plug under the box not seated properly. It's fairly common.

[davidt]

Some views of the underside of the fuse box, I doubt the printed circuit board is cracked as its a very strong well made piece of kit.

S1035380.JPG

S1035383.JPG

S1035377.JPG

[Brianmoooore]

It is indeed very well made, but it's still breakable with enough effort!

[ecsk]

I didn't mean cracked circuit board, I mean hair line crack in some solder joint of the board due to age, they are common electrical problem in old BMW.
I'll open it to check the plug again.

[ecsk]

https://www.bimmerfest.com/threads/brak ... op.436514/

I wish my problem isn't this, broken solder joint on pin 8 of c114
https://photos.google.com/share/AF1QipM ... h4dkl3RHpn

Can I turn the upper part of fuse box 90 degree if I cut some cable tie under glovebox ? want to unplug that c114 to see the solder joint, i just worry that I'll break other thing

[Brianmoooore]

Don't be afraid to pull on the wiring under the fusebox deck - you won't do any damage, and if you can identify a cable tie that is restricting things, then it won't hurt to cut it. Just make sure you don't pull hard on wires in such a way as to strain the joints on the circuit board.

[davidt]

Save yourself a lot of work with a borescope snake camera.