Ammeter behaviour and ignition light on questions

[David Womby]

My car has an alternator with an internal regulator fitted in place of the original dynamo and regulator. Recently, the ignition warning light has refused to go out. It glows a bit all the time. I read that is an indication that the charging system is not working and there being an imbalance between the voltage coming from the battery and that from the alternator.

I checked the battery - 12.6V when the engine was off. 14.4V when the engine was running. So, those seem to indicate battery and alternator are working. Then today, driving, I noticed in a short distance today (say 3miles) the ammeter read as follows (all readings are approximate)

Ignition on, engine not running 0A
Starter engaged -20A
Engine running at idle - +20A
Driving +20a then a sudden drop to 0A. A few minutes later it was back at +20A then it dropped to 0A again, then up to 15A and stayed there until the engine was turned off.

I don't have experience monitoring an ammeter but is that normal? I'd expect it to stay + charging and gradually drop to 0 as the battery became recharged not drop to 0 then jump back up.

Any insights into this behaviour and/or the dimly glowing ignition light would be appreciated. Thanks.

David

 

[Gold Rush]

With none MOPAR configuration it's difficult to say but I'd be looking at the self regulated alternator very closely. Take it to Advance Auto or Autozone and have them check it out.

 

[72RoadrunnerGTX]

Dynamo? Ignition light? What are you working on?

 

[khryslerkid]

That wouldn't happen to have a Lucas electrical system?

 

[David Womby]

With none MOPAR configuration it's difficult to say but I'd be looking at the self regulated alternator very closely. Take it to Advance Auto or Autozone and have them check it out.

Thanks. I did but all they could do was a battery load test. Their fancy computerized tester needed to know the year, make and model of car and didn't go back before 1991!!!!!

Dynamo? Ignition light? What are you working on?

It's a 1964 Bristol 408 but fitted with 1978 LA360 engine with an alternator that has an internal regulator.

That wouldn't happen to have a Lucas electrical system?

LOL - no. It's electrics were originally all British including Lucas dynamo and voltage regulator but they have been replaced long ago.

David

 

[RJRENTON]

With none MOPAR configuration it's difficult to say but I'd be looking at the self regulated alternator very closely. Take it to Advance Auto or Autozone and have them check it out.

Taking the questionable alternator to an auto parts store, such as Advance Auto, and asking them to test it, without knowing what tests will be performed and how they (the tests) will be administered is useless. To test the alternators capabilities it needs to be connected to a variable load, with output amps and voltage measured, with the unit driven (rotated) at a specific RPM. Just handing it over to a counter person, saying its not working, will prove useless. Why don't you communicate with the alternators manufacturer to determine possible fixes or at least, how to successfully test it. Just my opinion of course.
BOB RENTON

 

[David Womby]

Thanks for the replies. Feeling a bit foolish here but the ammeter behaviour seems to be caused by the electric fan. When it's running the ammeter swings to +20A and drops to approx. 0A when the fan cuts off.

I still can't figure out why the ignition warning light stays on though!!!

David

 

[72RoadrunnerGTX]

When it's running the ammeter swings to +20A and drops to approx.

The fan is drawing it's power from the battery side of the ammeter. Connected to the battery directly? Running an ammeter, all loads need to be on the alternator side of the ammeter. Any loads added at the battery with register as false charging current.

 

[David Womby]

The fan is drawing it's power from the battery side of the ammeter. Connected to the battery directly? Running an ammeter, all loads need to be on the alternator side of the ammeter. Any loads added at the battery with register as false charging current.

Thanks. Should I rewire it to source its power from the alternator side then?

David