2001 DGC battery light came on the other night. It starts just fine, so I'm ruling out a bad ground from the neg battery post. Driving it home I noticed that the headlights and all dash illumination flickers. Using a VOM, with the engine off the battery reads 12.5 volts. Starting and revving the engine at idle brings it up to about 14V. I can hear the engine pulling against the alternator when the regulator cycles on and off and watch the voltage across the battery (or at the alternator + post) climb to 13.4V when charging, then drop to 12.5 when the regulator cuts out.

I completely cleaned and wire brushed the crusty connections at the battery terminals, including the smaller gauge wires bolted to the posts. It's not a connection issue.

Attempting to rule out the battery I disconnected it and jumpered the vans cables to our other car and started the van. Within 10 seconds the battery light came on again, dash lights flicker, etc.

So, voltage regulator? Is it internal to the alternator?

Thanks,

Weekender

 

The voltage regulator is built into the PCM. The PCM uses a battery temp sensor (also built into the PCM) along with electrical load sensing to determine how much power to generate. The electrical tests you conducted actually sound ok IF you didn't have any electrical accessories turned on at the time. The PCM wasn't sensing much electrical load so it put out 13.4-14 volts. Try the test again but turn on the fan and headlights. Then rev the engine to 2500 RPM. I bet you'll see a bit higher voltage.

As for the flickering, here are two possibilities. There's an electrical connection right under the battery tray and that's a known corrosion spot. So check that out. If you find corrosion, clean it up and reseal the connection. Also, the headlights are powered through the front control module located in the intelligent power module. That entire unit can develop corrosion issues. So pull the FCM and check the pins for corrosion. If you find any, check the circuit board for corrosion. If you find any, replace the entire IPM. Nobody has had long term success by cleaning it.

 

Rick,

Thanks very much for the detailed reply. I did not have any accessories on while conducting the tests so that's a plus. I'll pull the battery tray and look for the connector you mentioned.

Is the IPM the module in front of the battery? There is a device there with two multi-pin connectors.

I'll investigate this afternoon. Sounds like I'm going to the U-pull-it yard for a couple of spares.

Regards,

Weekender

 

Ok,

The module between the headlight and fuse box, ahead of the battery, is apparently the ECM. Got it out, opened it, and it's completely potted. Nothing to do here.

I discovered that the FCM is the small silver box attached to the front of the fuse box. Got it off, removed the three torx screws and it apparently doesn't open without some judicious prying, or destroying the case, which I stopped short of.

No corrosion found on any pins anywhere.

The ground connection under the battery tray looked ok when I disconnected it but it's now cleaner and tight. Running out of ideas but I do find on the web that these type problems are not uncommon.

If I get another FCM out of the salvage yard, is there programming specific to the vehicle that will keep it from working? VIN, Mileage, options, etc.

Any further advice, short of taking it to a dealer, would be most appreciated!

By the way, it's a 2002 DGC Sport, 3.3L w/ 150,000 miles.

Thanks,

Weekender

 

Last symptom.

After getting everything back together, there was no change. Start the van and in about 20 seconds the battery light came on.

I took a small plastic mallet and tapped the FCM several times against the IPM. I tried it again, this time with the hi-beams, AC and radio on and the battery light stayed off and the dash lights didn't flicker.

I drove it around with all of these accessories on for about 10 minutes and everything was fine. Turning off all the accessories, the battery light came back on in a few seconds.

Going to look for a clean, used IPM / FCM but also keep my '94 Volvo 940.

Weekender.

 

Have you not considered the alternator as the problem? Unless I missed it, I would have taken the alternator out and had it bench tested.

 

I have considered it but haven't for two reasons. One being that it was replaced a year ago by the previous owner, a neighbor and friend, (but could be failing) and the other is that the battery is being charged and as long as the AC, and headlights are on, the battery light stays off.

I'll hunt for an FCM and IPM this weekend. If that doesn't work, I'll have the alternator tested.

Thanks,

Weekender