Yesterday, my red battery light came on and my interior lights were flickering when the door was open.

I picked up a new Alternator (120Amp), and replaced the original 90 Amp alternator. Everything worked great, for 5 minutes. Then the red battery light came on again.

Early this morning, I took the van for a drive, requiring the headlights. Everything OK for 2 mins., then the red battery light came on again, and my headlights and dashboard lights began to go very bright, then back to normal.

By the time I got home, the Temp. Guage, Fuel Guage, and Odometer were cutting out when the engine was revved up over the idle speed.

I used my digital voltmeter on the battery, it reads 12.6V. with the engine OFF. With the engine running, it read 13.7V. last night, and now reads over 17.5V this morning.

I checked the PCM for codes, and it reads Codes 41 & 46.

41 = Alternator Field Not Switching Properly; an open or shorted condition detected in the alternator field control circuit.

46 = Charging System Voltage Too High; battery voltage sense input above target charging voltage during engine operation.

I understand #46, as this explains my lights getting brighter.

What does #41 mean? A problem with my new alternator, or the voltage regulator in the PCM? Or both?

Thank you.

 

yep it could be both. could be a wiring problem... could be a lot of things. the PCM is the voltage regulator. it could very well be bad and there was actually nothing wrong with your original alternator. BTW did you have the original tested? I find it's really rare for these alternators to actually go bad (except brushes and commutator rings)

 

Problem found.

The wiring harness from below the battery that goes over the transmission had a broken wire, and it was grounding against the transmission housing.

3 hours later, the excellent Dodge mechanic had it fixed.

He also suggested I leave the new 120A alternator on the van, as it provides more power.

Without testing it, I know the original 90A alternator I removed still works.