72 Ammeter shows discharge

[Richard R.]

Recently installed a new battery and rebuilt alternator. Ammeter always returned to center after vehicle was started a run for a few seconds. Last night I had to use the headlights and the needle feel to almost -40, turned the heater blower motor and discharge when about -20. I have not used he headlights all summer so don't know if it did this before last night.
I checked the voltage at the battery with lights on and engine running at 1300 rpm and got a reading of 14.8 volts. Figured the ammeter was bad and replaced with a new one, Same results as before. Need some suggestions on we're to start looking for the problem.

[Edward J.]

Re: 72 Ammeter shows discharge

Richard, Did you have a charging problem before you replaced the alternator? Normal charging rate is about 13.8/14.2 with a fully charged battery.

[Richard R.]

Re: 72 Ammeter shows discharge

Battery was 5 years old so I replaced it. The alternator was only. Charging at 12 volts so I replaced li.

[Edward J.]

Re: 72 Ammeter shows discharge

Rich, sounds like something is up with alternator.

[Richard R.]

Re: 72 Ammeter shows discharge

Would you still get 14.8 volts at the battery even though it shows a discharge on the gage?

[Edward J.]

Re: 72 Ammeter shows discharge

Rich, 14.8 should be showing the +side on the amp gauge. At 14.8 with a load on it sounds like the voltage regulator is stuck on. There maybe more than meets the eye internally in the alternator. I can not explain what is up with the neg. discharge on the Gauge, I have seen some weard things in my years and have rebuilt many alternators over 40 years as a tech. If I had to guess I would say the voltage polarity is reversed, meaning since your gauge shows the opposite some is crossed internally.

[Richard R.]

Re: 72 Ammeter shows discharge

Thanks I will get it checked tommorow.