I've been chasing an electrical problem on my 91 DX hatch. While driving with the headlights on, whenever I hit the brakes the dash lights, headlights, etc dim slightly. I've done some research prior to posting, and I am led to suspect a grounding issue. I also have an intermittant issue that has been getting worse where the starter will click several times before engaging, but after several attempts will turn over the engine. Ambient temps or engine temps make no difference so I don't think its a heat soaking issue.

The only aftermarket add-on to the electrical system is a tach, wired to a fused circuit and grounded to the chassis. I've disconnected it to rule it out as a cause, no change.

I replaced the starter as it was getting worn (249k miles on the original starter).

I previously had a diode issue with the alternator, and recently replaced it. The problem was present before and after replacing the alternator, but the diode issue is obviously resolved.

Battery is 1.5 years old, rated 500cca, measuring 485cca with a midtronics tester.

I have checked and verified the battery cables are tight, terminals are clean. As I said before, I suspect its a grounding issue. I have both valve cover grounds clean and tight, transmission/chassis ground from the battery negative terminal are clean and tight. I load tested the valve cover grounds and battery negative cable with a head lamp bulb (high draw bulb will reveal high resistance in the circuit). I added a redundant chassis and engine ground by attaching a battery jumper cables from the battery negative to chassis and engine. I feel confident I've ruled out anything from the battery to chassis ground, and engine to chassis ground.

Any thoughts on where to check next?

Thanks!

 

Look in your taillight sockets. If there is corrosion in them, there is your problem. Reseal the taillights and you are done.
Regards
Dave