Amp meter on 39 Desoto not working

[desoto1939]

I hope I get you to look at this just by the topic.

 

So here is the situation on my 39 Desoto.

 

i noticed the other day when driving home from an event the amp meter was not pointing to the charging side or positive side on the gage.

When I hit the brakes the amp show discharge.

Also note that the battery is 8 years old, yes 8 years old.

over the weekend I tried to start the car but had a dead battery.

Put in a new 6v battery and also charged up the battery on a 3 amp trickle charger.

Started the car and it started real fast and strong but the amp still did not go to the positive side to show that it was charging the battery.

 

I did find the issue why the amp gauge was not working but want to get the members to put on their thinking caps to see if they might have the answer to what happened.

I  did think it might be that the generator needed to be rebuilt since it is the original in the car from what I can tell since I have owned the car since 1987.

 

Post you quesses and answers and then I will post how i fixed the issue and what the cause of the issue. After making the fix the char is now running and the amp gauge does go to positive when starting the car to indicate that it is charging the electrical system

 

Rich Hartung

desoto1939@aol.com

 

 

 

[maok]

Most likely the generator or regulator not supplying any power to the battery.

 

Does the amp meter  needle sit steady on the discharge side? Say at about 7-10amps?

[Merle Coggins]

The fact that the ammeter would show a discharge when power was consumed leads me to believe there is nothing wrong with the gauge or it's connections. So it must be an issue with the generator circuit not putting current back to the battery. You say that you though it may be the generator, which leads me to think it probably wasn't a generator issue. That leaves the regulator and associated wires. I'm guessing it was a simple fix once you investigated things. Possibly a loose connection at the generator or regulator. Or possibly a broken wire at one end. Either way the generator output wasn't reaching the ammeter.

[John Reddie]

The first thing I always check is all connections in the charging and battery circuits for corrosion or looseness and of course, the battery voltage. If all checks out well there, I remember that back when I had some of these six volt Plymouths and Dodges and a no charge situation like you describe occurred, with the engine running, you could briefly ground (I think it was the field terminal) on the voltage regulator while having an assistant observe the amp gauge. If the needle pegged up on the charging side of the gauge then the trouble was in the regulator. If nothing happened and the needle remained on the discharge side, then the generator was the problem.

John R

 

[Dodgeb4ya]

Sticking regulator contacts

[Plymouthy Adams]

nah...just tightened the generator belt...

[greg g]

If your old battery had bridged cells causing an internal short, it would not take a charge.  Depending on where the short was it might show a discharge with the key on and small load of the ign system.  Conversely a new fresh fully charged battery might not call for a charge even after a few start cycles. The regulators job is to sense when the battery is low and to recharge it then.  So a brand spanking new battery in a car that starts easily the regulator might allow the Genny to idle till it sensed a sufficiently low charge condition before it closes the cut out points. Step on the brakes with the hih beams and heater blower on full and report back.

[desoto1939]

I like that our experienced members have been reading my post on the situation with the amp gage.  So I have read all of the posts and one of the members came up with the solution to the issue.

 

My forst thought was that the regulator had some sticking points so I headed in that direction.  The regulator is located on the driver side high on the cowl.  I started to look at all of the connections and then noticed that the wire which is a 10 gauge wire that should, should be connected to the FIELD contact point was broken off and it looked as if the wire had gotten overloaded and had a  burn mark onthe insulation and all the wires had been cut and the connection was lost to the regulator.

 

I  then used a brand new wire to connect the field connection onthe generator to the field contact onthe regulator.  I then crossed my fingers hoping that there might not be any other issue.

 

I started the car and then amp meter was now showing a charge and the needle was pointing at the 10-12 amp rnge becasue i had tried to drain the battery by just having th elights on for approx 20 minutes prior to making the new wire.

 

So thanks to all that provided input to the issue.

 

So yes check all of your connections ever so often and always check for the obvious point of loose connections or a broken wire.

 

Hope this was a lesson that someone else might benefit from.

 

Keep up this great forum for us mopar owners.  i love reading the issues that other people are trying to slove and like it when they post how they solved the issue.  This helps everyone learn more about their cars/trucks.

 

Rich Hartung

Desoto1939@aol.com