Crazy electrical problem

[AnkerB-S]

I have a really crazy electrical problem.

When I turn the key to the run position and test the horn, emergency blinker and turn signals they work like a charm. If I start the car they will stop working after a while. Since the horn is on a different relay than the blink relay used by the emergency blinker and turn indicator it must be either an electrical supply problem or a grounding problem.

When it is close to failure the horn and flashers will work intermittently and I can hear the relays buzzing instead of clicking. When they fail there is no sound from the relays.

Strangely the head light switch works fine all the time and I can switch between high and low beams with no problem.

My problem is that I can't find the chassis grounding point for the instrument panel. Will appreciate if someone can tell me where it is.

The car is a 1987 1700 Supersprint. It is a mix of a pre-1988 and post-1988 1700. It is a LHD USA model.

Thanks/Anker

[Jonathan Kay]

Private Message sent.

Jonathan

[SM25T]

Often turns out to be corrosion inside the hazard warning light switch. Work the switch heavily a few times. The earth point for cars 2000-vintage is a stud on the wiper motor bracket.

[AnkerB-S]

So, after two days of effort, I found the problem.

Most of the time, I was sure it was a grounding problem. I did find both ground points. Yes, one was hidden on top of the wiper motor bracket. The other one on the oil cooler bracket. Also very difficult to spot. Because the problem was heat-related, I thought it had to be the ground point on the oil cooler and ran a wire from there directly to the negative battery terminal. It didn't help.

So, this morning I decided to use the fact that both the horn and indicators were failing had to have significance. I printed out multiple copies of the wiring diagram and traced all connections to and from the indicators on one sheet and the horn on another. They are both powered through independent fuses from one terminal on the alternator. When I checked those, I found that one was loose and needed pinching, and another was loose, but just had to be pushed fully in. Then everything worked as it should!

The prior owner had lived with the problem for a long time and had tried replacing the flasher unit.

Jonathan was a huge help. What a great resource. Thank you, Jonathan!

A very relieved and tired Anker.

[SM25T]

Good result.