Strange electrical problems

[prclayton]

Hi,

I have been having odd electrical problems on my Isuzu for some time now. Actually for the last 5 years. Two odd ones I do have are charging current, and aparently poor voltage to the internal electrics of the car.

1) The alternator and regulator are OK. I say this, as I had it tested. The alternator puts out 13.8 VDC, but I only see 13.2 at the battery. This problem seems to suggest a voltage drop across the wires, but bridging does not make an difference. When I put the headlights on high, the battery voltage drops to as low as 12.6 and the alternater can't keep up and drops to 13.4VDC.

2) The next problem may be related to the above. When I put my indicators(turn signals) on, the volt meter internally jumps up and down quite noticeably. The internal fan does not blow very hard, and at best I measure 11.5v on the motor on high 2 volts lower than what it should be. The aircon cuts in and out with long breaks between cutting back in. The power windows are very slow, the door lock solenoids don't work smoothly. Yet I cannot seem to find anything that suggests poor circuits.

Anyone had similar problems. This model is 2.6L model with 4ZE1.

regards

[amigo-2k]

Have you ever replaced the alt before? If so, what brand is it and where did you purchase it from?

[Cat Fuzz]

Your alternator could put out 14 volts all day but if its not keeping up with the current demand, its useless. The fact that voltage keeps dropping when you increase the load suggests a weak alternator. A simple voltage test with no load is not an accurate test.

The typical auto parts store alternator tester can usually only tell for sure if one is bad. They can, and do, give false positives because they don't put a load on the alternator.

[prclayton]

Today I replaced the regulator, and did a small mod to raise the ground reference to put out a bit more voltage which worked a treat.

So taking the the multimeter I monitored the battery voltage with a charger in place as well, and using the turn indicator, the internal volt meter still jumped up and down, but the voltage on the battery remained contant within a few millivolts.
I suspect that I have an earth fault hr, but don't know where the earth is for the dash instruments.