I have a 2001 E250. While driving it today the battery light came on and the guage was topped out. By taking my foot off the accelerator or turning on various devices like the fan on high I could get the needle to come down. When I was stopped at a light it would come back to normal.

I got back to my shop with everything on with the needle indicating just a bit high and the light on whenever I had my foot on the accelerator at all and it back in normal when idling.

I was assuming the alternator was bad at first, but maybe the voltage regulator?

I glanced under the hood and the alternator looks tought to replace, I don't even know how to locate the voltage regulator.

Any thoughts and ideas would be much appreciated. My mechanic skills and knowledge is limited.

 

Charging System — Single Generator

THE CHARGING SYSTEM WARNING INDICATOR IS ON WITH THE ENGINE RUNNING AND THE SYSTEM INCREASES VOLTAGE
CHECK I CIRCUIT 904 (LG/RD) FOR SHORT TO GROUND
1. Unplug Generator C198 plug.
2. With the ignition switch in the RUN position, check the charging system warning indicator.
Is the charging system warning indicator illuminated?
Yes
REPAIR I circuit 904 (LG/RD) for a short to ground. TEST the system for normal operation.

No, INSPECT GENERATOR S TERMINAL C199
1. Turn the key off.
2. Replug Generator C198 plug.
3. Inspect generator S terminal C199 to make sure it is correctly mated to the generator and making contact with the S terminal.
Is generator S terminal C199 OK?
Yes
Start the engine.
Note:
Generator S terminal C199 must be connected for this test.
With the engine running at 2,000 rpm, measure the voltage between generator S terminal C199, circuit 4 (WH/BK), component side and ground.
Is the voltage greater than 5 volts?
Yes
INSTALL a new voltage regulator. TEST the system for normal operation.

No
INSTALL a new generator. TEST the system for normal operation.



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Thanks so very much for your help.