Our 75 2.0/FI car has completed a two year restoration that included an engine and transmission rebuild, along with rebuilding or replacing all FI components.

The car runs perfectly all the time until it has been running with electrical load for 30 min (radio w/Bluetooth, rear fan) and then I turn on the headlights. The car immediately starts to sputter and will die unless the lights are turned off, which puts the car back to perfect.

We initially thought that it was a bad ground in the headlight circuit, but cleaned and verified, no red flags there.

Is it possible that the mounting plate for the regulator has a bad connection? I think it is original to the car.

Any help would be greatly appreciated as last week I had no lights coming back from the first cruise.

Thanks

Have you measured voltage under these different load conditions?

Yeah, what van said. I would suspect the regulator just due to recent issues with the old buggers (used and nos) not ever being able to kick good voltage to the battery.

I would also point towards some strange ground issue at the rear. I had quite a bit of luck checking resistance to ground from various points on the motor in my search for low charging issues. Fan shroud to ground, starter, etc.

Start with the basics as suggested above.

The headlamps are the largest electrical load on a stock 914.

Sounds like you're getting low battery voltage and when you apply the large headlamp load it collapses the battery voltage. Probably to the point that the coil or the ECU no longer have adequate voltage supply causing the mis-fire.

Quickest fix will be testing with DMM in a methodical manner.

Thanks for all the feedback! Will report back.

What happens when you turn off the aux fan? Is the idle low when everthing except for the lights are turned off? Does the gen/alt light flicker?

Nothing noticeable and no Gen light.