Battery volts drop

[BDR_Boy]

Resurrecting an old thread. I'll be the 1st to admit, I'm electrically illiterate.

I've got the same problems as allcarfan had. It appears I take a hit when switching on ANY accessory... fan switch... lights... wipers... heater... and with each accessory turned on... the voltage drops a little further. I can actually make the volt meter on the dash drop from 14 down to about 11 very easily. However... to this point I've just kind of lived with it... the cooling fan seems to have the least affect and doesn't affect operation of the car during the day... and I never use the heater... so... it's been a daytime driver only.

However... just this past weekend I was stuck out & about after dark, so I had to use my lights for the short trip home... and... when the voltage dropped... some of the other gauges began to act wacko too... for example the temperature gauge started slowly going up & then back down by about 10 degrees C... despite it being a cool night and no cooling system issues.

The multi-meter indicates at the battery... and also at the alternator... that the alternator is charging at about 14.55 volts max and the dash gauge reading about a 1/2 volt off at 14. With all the accessories running... the multi-meter might drop down to about 14.51... while the gauge on the dash will drop down below 11. If I'm getting the desired voltage at the battery at all times... with, or without, accessories... doesn't that rule out the alternator/voltage regulator?

Maybe I'm wrong (remember, I said I'm electrically illiterate)... but I'd almost bet it's a grounding issue... maybe corroded... maybe loose. I have VDO gauges... and I've read where VDO temperature gauges need to have a separate ground. However... before I start taking things apart... can anyone tell me where the ground(s) for the dash components on a BDR (#509 here) are typically located? Hoping to narrow down the search before starting to dig "in search of".

Any other advice appreciated.

allcarfan... it's been a year... what have you found on yours?

[allcarfan]

I never could figure it out, nor could the shop. I just live with it. No adverse performance. I havent put many miles on in a year though. I had back surgery.

[patrickt]

Originally Posted by allcarfan

I never could figure it out, nor could the shop.

Well that's a piss-poor shop that probably didn't want to go to the trouble of running voltage drop tests along the circuit, both on the hot side and the ground side. If you have normal voltage at the alternator/battery, and not-normal voltage a distance away, then you "walk the circuit," while it's under load, looking for the spot of increased resistance, with your ten dollar VOM, that will have a voltage reading when you bracket it with your probes. Voltage doesn't just vanish and fly off like Tinkerbell. It's slipping away because of high resistance, like a bad crimp, poor soldering, loose ground, or a broken wire inside the insulation. The only way you can test for it is when it's under load, and it takes a little patience. But it's not brain surgery.