Electrical gremlins

[gordon]

No wipers, horn or cigarette lighter. Fuse no 2 is good ( screen wash pump works.   An independent supply to the wiper makes it run.
Horns, nothing live at the horns  with ignition switched on so I guess I've lost supply somewhere,  the horns work with a separate live supply,I can't see anything adrift on the back of the fuse board.

Any ideas anyone, any help would be much appreciated  1965 230 SL

[Mike Hughes]

If the fuses look good, sometimes the fuses just need to be rotated around in their sockets to clear up the little bit of corrosion that can accumulate there to re-establish good contact and complete the circuit.

[gordon]

Thankyou Mike, yes I've thoroughly cleaned the fuses and holders

[BobH]

Hello, possibly a bad earth connection, have a look at the earth/ground point below the dash. The horn, cigar lighter and possibly the wipers may all  get their earth from this position, whereas the washer pump probably picks up an earth local to the pump, hence why that's still working

The earth point is shown on here

https://www.sl113.org/wiki/Electrical/Ground
 

[gordon]

Thanks for the grounding suggestion, everything looks clean and tight so I'm still looking for an answer!

When I fed a live to the horns they sounded immediately but surely this shouldn't happen until I press the horn ring to ground it.?  Any more ideas?

[BobH]

It does sound odd, perhaps Mr Peterssen can offer some suggestions, but in the meantime, i would start testing out the circuits, and double checking the earths, as this still seems the most likely

There should be a permanent +ve supply at the horns, and a switched - (earth) through the horn ring, so if you are applying another +, and making the horn work, then this indicates that you have a permanent earth there, which is incorrect.  Perhaps break apart the 12 way connector under the dash, that's connected to the steering column switch,  and then start metering out the circuit to the horn, and see if you still have an earth at the horn

I'm not sure how this would affect the feed to the cigar lighter or the wipers, perhaps there's a short on the loom, which is affecting these other devices, you may find this by a process of elimination, once you start disconnecting circuits

[Paul & Dolly]

Hi Gordon,
I find that the best place to usually start is to answer the Question:

What was the last thing that was done to the car before the problem commenced ?

Also the horn wireing catches out many, as they are fed with a LIVE and switched to EARTH via the horn ring - as BobH mentions, so I would be suspicious if there is no supply at the Horns.

Good luck

Paul

[gordon]

Ht thankyou for all your support , after undoing and remaking lots of connections everything now works as it did before, I've no idea what I did to get it to fail or how I fixed it! Thanks  again Gordon

[rwmastel]

Similar to spinning or cleaning the fuses, I guess other connections just need refreshed.  I'm starting to preach about using FACTS when troubleshooting.  Earlier in the thread you said "Thanks for the grounding suggestion, everything looks clean and tight so I'm still looking for an answer!"  That is an assumption that the grounds are good.  If you remove and clean, then you know.  You ended up touching several connections/grounds and got it working, which is great, but systematically testing each thing is best.  Just advice for everyone for the future.

[lpeterssen]

Thanks Bob for suggesting my advise.  Currently busy on a wiring harness project for a customer in Germany.  Interesting project, will post pictures soon, with description of the custom work developed for him.

Maybe tomorrow will have a rest and will think over this particular case