I've got some electrical issues and would really appreciate some help form any Rennlist electrical gurus. My airbag light started to stay on and the check lights were very dim and virtually unreadable when you turn the key, I also had an intermittent working alternator gauge. The hammer tool showed a bad ground for the airbag light so I disconnected the cluster, pulled the grounding posts in the back and gave them a clean.
Now I get under-reading instruments (even the RPM hardly moves) and no alternator reading. The freaky part is that when I put my foot on the brake all the gauges fall to zero! Any help greatly appreciated!

 

Check the grounds...

 

Thanks 75ohm,

I've pulled the cluster again, fiddled and re tightened the four "football" grounds and I've just finished doing one of the under dash chassis ground points. Is there anything inside the cluster that I need to check?

 

That's a good start - what are the results now?

 

I went through and cleaned everything again and pinched in the female contacts on the ribbon connectors. I seem to have fixed the airbag light problem. Now I have an intermittent problem with the brake switch effecting the gauges. Every time I hit the bake pedal all the gauges drop to zero and it coincides with no brake lights. Sometimes it does it, sometimes not. The other big one is that when I turn the key all the check lights don't come on. I wonder if that could be the ignition? I think there is another ground in the center of the dash area that I'll need to check.

 

Airbag still on. If I turn the key with my foot on the brake I get all the check lights. I'm not sure what's going on between the brake switch and my check lights. It does seem like a ground issue but I'm stumped!

 

Now that's peculiar... pull the brake switch...

 

Probably a worn-out voltage regulator. I suspect battery could be shot, alternator/voltage reg. isn't doing it's job.

 

Sounds like the soul of Lucas has invaded your 944. An exorcism is the only cure. Seriously though, it's probably one of several grounds that get hinky from old age. Even the contacts on the cluster ribbon strips are suspect on these cars if you live where it's humid.

 

Steve... good point on the ribbons... wonder if some cleaning on the edge contacts wouldn't help there...

 

Voltage drops too low and the running condition would stumble...no?

 

Hi All, When I had my instrument cluster out to do the light refurbish I used MAAS Metal Polish on the football shaped contacts. I put a cut off Q-Tip down in the holes so no polish would go down in them. I even polished the nuts and threaded part. Cleaned all up with alcohol, cleaned off where the three clamps slide onto. I have not had a problem since. Look for any place a Brown Wire (Ground) is connected and clean it. It sounds as if the brake switch is going out or needs to be cleaned with electrical contact cleaner.

Cheers,
Larry

 

Thanks guys. I'm thinking more of a sacrificial burning! Seriously, I thought all my electrical woes were over when I gave up Italian cars. Needless to say it is kind of entertaining to watch your gauges die when you hit the brakes. The alternator was replaced about four weeks ago. I'll go through the grounds again and see what's up with the brake switch. I paid special attention to the ribbon connectors. Could the ignition switch somehow be involved in all this? More importantly, do I need a German priest to perform the exorcism?

 

I would look at battery and alternator before anything else.

 

I would check and clean all the earthing points including the main earth strap and ground points between the engine block and bulkhead behind the cam cover . Also there is a triple earth point below one of the headlight pods that gets rusty and the ones on the rear valence
Wouldn't hurt to remove and replace the ignition switch connectors to make sure they have a good electrical conductance