Alternator Wont Charge

[mikeynags]

Hi everyone,

Today I started up the RR to see the ammeter discharging and my voltmeter only reading about 11.8 volts. Battery reads about 12 volts between the terminals when the car is running. As soon as I pull the negative cable the car dies. I am measuring about 20 volts on the output of the alternator itself (which I bought brand new this summer along with a brand new voltage regulator) and I also measured 20V on the connector going into the firewall. I pulled the voltage regulator and measured 12 volts DC (with the key in the on position) between both pins and ground per the instructions of the troubleshooting section in the Mopar service manual. Also, I changed the VR and no luck either.


Any ideas on where to look next???
thanks,

 

[mikeynags]

Some more info. This summer I put a new powermaster alternator and voltage regulator in the car. It has been running just fine until today. I started the car and immediatley noticed the discharge on the ammeter. Looked down at my autometer gauge and saw that it was only reading about 11.5 volts. Normally, it reads about 14.5V and fluctuates a bit with throttle. I am not seeing any fluctuation at all. It just stays solid at 11.5 with or without throttle. Any help would be greatly appreciated.

thanks,

--mike

 

[68ChargerAG]

I am no mechanic, but here are a couple things I would check. Ensure engine is grounded to firewall. If you are getting 20V out of the alternator but engine dies when battery is disconnected it seems that the battery is acting as the only engine ground for ignition. Voltage regulator might be fried also, even though it is pretty new the points might be fried from that high voltage. Some of them you can pop opened to see how the points look. I have even cleaned them up before like you could with ignition point type distributors.

 

[Meep-Meep]

Checking/adding grounds is always a good idea on our older cars.

If you are getting 20V out of the alternator that would indicate you are getting voltage into the field terminal - and probably a full 12V, which is not good. The B terminal of the ALT goes through the bulkhead connector, through the ammeter and ends at the starter relay with a fusible link (69 RR example). Check the link for continuity. If you have a bad link and you fix it, you should get the 20V you measured at the SOL and the bat - again, too much voltage for the battery. You also want to remove the bulkhead connector and clean the terminals. Bad connection = high resistance = heat = melted connector.