Help with Charging issue
 

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,

What condition is the battery in ? What do you get with engine off just from the posts with the meter ?

I get about the same 12.2V with the car running or not. The battery is about 2 years old.

if the alternator that you purchased has 2 field terminals-you need to ground one of them.

I have the output and 2 fields and the wiring harness has to field connections. Why would I have to ground one? This just started happening. Thanks for your help on this.....

i guess i need to ask-what year mopar are we discussing? and if you are pulling battery cables while the car is running with solid state regulators-you run a chance of frying regulators.

it's a '70 Roadrunner. I put a new alternator and voltage regulator in the car this summer and things have been fine until today. Now, I get about 12V on the voltmeter when running. Normally I would see about 14.5V across the battery with the car running. Also the ammeter is visually discharging. It's never done that until today. No more pulling of the cables ....I promise :)

depends on if you have the original style regulator (electro mechanical). If you do have it, this was designed to work with a alternator with only one field terminal. As stated, you CAN use the dual field alt IF you ground one of the field terminals. Dont matter which one. Of course the newer style electronic regulators require the use of the dual field alt. Is that a misprint of "20 volts going into the firewall"?

my guess: diodes starting to go bad.

Yes, I measure 20V at the firewall yet I don't see it reflected on the ammeter. My hope is that the new powermaster alternator I installed in June this year is the culprit.

Update: Pulled bulkhead connector apartbased on article I read here: http://www.madelectrical.com/electricaltech/amp-gauges.shtml

and it looks like I am a victim of this problem. Does anyone have any good details on how to remove the dash? I would like to re-wire according to the article but having a tough time trying to get the dash out. Any help would be greatly appreciated.

thanks,

--mike

very good info. will have to store that in the back of my head