Bloomin Horn and Heated Window

[ORB 227 1 Cars]

I’ve been chasing an electrical fault on my 1992 205 GTI where the horn, heated rear window (demister) and cigarette lighter all stopped working together.

 

After a lot of poking about I’ve found they seem to share a common feed through Fuse 8 and the connectors on the back of the fusebox.

 

Here’s the odd part:

 

• Horn works fine from stalk and if I power it via the relay in the bay.
• As soon as I press the demister switch, everything dies — horn stops, demister relay drops out, and the lighter loses power again.
• If I pull and refit Fuse 8 and the demister relay and cycle the ignition everything comes back to life until I hit the demister button again.

 

 

I’ve had the fusebox out, cleaned it thoroughly, checked all continuity and voltages, sprayed the contacts with cleaner, and can’t see any burnt tracks or corrosion anywhere.

 

It really feels like the shared feed between the horn and demister relay is dropping voltage under load — maybe a bad splice or dodgy connection somewhere in the loom near the fusebox.

 

Has anyone had this same issue before, or know exactly where that shared feed / splice sits on a right-hand-drive car?

Any other suggestions welcome before I start unwrapping the loom!

 

** shamelessly I wrote this using AI as I spoke into it.

 

** anyone know a good ad blocker for the iPhone for this forum? It’s become really hard to navigate 

 

Edited Sunday at 08:15 PM by ORB

[SRDT 209]

Looks like the usual hidden solder joint problem, fidling with the rear window relay can fix it for a short while as it's right under there. Sometimes it can also fix itself after a few hours/days as long as you don't try to draw too much current.

 

 

 

[ORB 227 1 Cars]

Thanks for the reply. 
 

I did a load more testing and decided that it must be due to a dodgy tract within the board. I could not get the bloomin thing fully to bits to test it or examine it as it’s within the layers? 
 

so, I made the below: took an old style fuse, cut off sole insulation and soldered a wire to the cold side of the fuse leg. I then removed the cover from the relay and drilled a wire sized hole, threaded the other end through and soldered it to pin 36. Rebuilt and it seems to have fixed my issue. I hope. 
 

Thanks again SRDT for replying, I’ll let y’all know if it lasts or sets my car on fire.

 

Tell me if I’m wrong, I’ve had a few Stella’s and I haven’t got my glasses on…

[SRDT 209]

It should work, it's pretty much the bodge that you can use to get the horn working for MOT:

 

As for fixing the fusebox it's not the copper tract that's dodgy but a solder joint. The relay connector is used as a bridge between the two plates and that put the hidden solder joint under too much stress.

As far as I know it's the only brigde of this kind so once you reflow this particular joint the fusebox is as good as new.