My Ford charging system is charging the battery just fine, but I have a Battery light on. I have had no problems with the battery running down. The ammeter stays on the + side and a voltmeter plugged into the cigarette lighter shows 13.1-13.5V when the engine is running. Measuring at the Alternator with the engine running I have 9-11V on the Field terminal, 0V on the Stator terminal and 13.5 volts on the Battery terminal. On the Voltage Regulator with the engine running I have 5v on the I contact, 13V on the A contact, 0 Volts on the S contact and 9-11Volts on the F contact. If I remove the wire to the I contact with the engine running I have 0 volts on that contact. I read about 5 volts on the disconnected wire. shouldn't I see regulated voltage on the I contact of the regulator? That would keep the Battery light out. I've had the Alt tested and told it was good, but I don't know if they look at S terminal output. I tried 3 different regulators with the same results. This system has worked fine for years but now the idiot light is on and I feel like an idiot because I can't get it out. The good news is the battery is being charged nicely. I did search this forum and couldn't find anything that matched my problem. I appreciate your help.

 

Welcome to FTE

So do you have a battery light or a AMP gauge?
The factory did not install both so we first need to know what you got.
If you have a AMP gauge you can not go by it as they never move to show charge or dis-charge.

Now on your voltage readings something is not right as the output of the ALT and at the battery you should see between 13.5 to 14.5 volts at idle.
If you turn on everything head lights on high, heater / AC on high, radio playing what do you get for voltage at the battery at idle & with the RPM up to 2000 RPM?

If you put 12 volts to the "F" stud (dont do this for too long) on the ALT you should hear the ALT change pitch and the volts go up to 15+.
That is called full field testing the ALT and if it changed pitch and the volts went up the ALT is good and the regulator is bad.

Now I said it could be bad is the connector connection good and clean both the plug and the regulator side?
Also the regulator needs to be grounded good where it is bolted down to. May want to pull it off and take sand paper to the REG & fender.
The other thing to check would be the wiring to / from the REG / ALT because if a wire broke the 2 cant talk and work together.

Right now I would say REG or ALT or both are bad but you need to do a full field test to see if the ALT is good.
Dave ----

 

When you pulled the I wire off the regulator, the dash light went out correct?

 

Yes when I removed the wire from the I terminal of the regulator the battery light went out.

 

I would buy a new regulator.

 

I would still put 12 volts to the field wire to make sure the ALT puts out.
A bad ALT could have taken out the regulator.
Dave ----