Overcharging

[lights_sirens]

When I started up my '98 P71 to leave work tonight my charging system went haywire. The idiot light for the battery was flickering so I parked the car, opened the hood, and check to make sure the battery terminals were tight and they were. So I started to leave the parking lot and the dash and interior lights quit operating (except for the idiot light). At first I thought I must have blown a fuse, but when I got to a stop sign the dash lights came back on for a moment. When the RPM's increased the lights turned off again. Thank goodness I had headlights and taillights (no turn signals).

When I got to a stop light there was enough street lighting I could see the voltage gage was reading very high (right below the red zone). When I got home I checked the battery voltage with the engine off and it read 12.54. With the engine on it read 16.2 to 17.2. The lights stayed on at 16 V and shut off at 17.

Questions:

Should I replace the voltage regulator first, or get a whole new alternator? (Car has 128K miles and there is no evidence in the service records of the alternator ever being replaced and a whole new alternator is only $70 more).

Do I still need to get it "bench tested" before investing in any parts?

I believe the "3G" police alternator (130A) is the correct one for my crown vic, right?

It's good to be back here!

[KimMG]

Some autoparts stores can test the voltage regulator and alternator.

[SCPDMechanic]

Definitley replace the alternator, on that vehicle the regulator is built into the alternator. It might be a good idea to replace the battery as well since overcharging can damage it.

It's a pretty simple job, all you need is a 1/2" breaker bar (to release the belt tensioner) and a 3/8 drive ratchet with an extension and a 10mm socket. After you disconnect the neg terminal on the battery, remove the serp belt then the four 10mm bolts on top of the Alt. Remove the main wire going to the alt and the plate above the alt should be free to move out of the way.

The two bolts in front of the alt (on the bottom) just need to be loosened about 1/4". Disconnect the regulator plug on the back of the Alt, and the whole thing should slide right out.

Good luck

[lights_sirens]

Thanks SCPDMech. You know your stuff. I was hoping you'd be wrong, but my battery was toast. Now my interceptor has a new charging system (total cost $180). I found a great deal on a new alterternator on ebay motors (search #7795).

I was glad the battery was the only item damaged by the extra voltage. That's the easiest alternator I've ever removed/replaced. It was the original Ford unit from 1998.