PFM Alternator Not Charging

[Extreme1]

Dave from Veracity Racing came by yesterday and was helping me with some issues with my car. One thing that showed up is that the alternator is not charging the battery. The voltage on the dash is showing 11.8 volts. That’s also what is showing when I hook up the UTC.

Any ideas where to start?

[Fred Michael]

First thing to check, make sure the belts are tight. They can seem tight enough and not be and they WILL slip. Beyond that, check the output at the alternator itself, I have had broken wires cause the battery to not receive the charge from the alternator even though the alternator was in fact working.
Bad alternators are also not unheard of

[Extreme1]

Thanks Fred. The belt is turning the alternator pulley, I can see it at idle with the engine cover off. I’ll check the belt tension. I’m sure it’s not slipping as I would hear the squeal like I can on my street car occasionally. Any idea which alternator terminals to check with a voltmeter? I’m thinking check the alternator first, then chase down thru the wires towards the battery.

[BeerBudgetRacing]

What is the rpm range that your alternator works?

A lot of us run dynamos on the zetec fc and they don't charge at idle.

Did you rev it and still see no change?

[David Ferguson]

We noticed the lack of voltage from his first on track experience. While not running full revs, it should have been charging, instead the car was running like a total loss.

For voltage output you want to check the post connected to the thick wire on the alternator. Should have a little white rubber boot over it. Probably connects to either the master switch or the starter.

[Extreme1]

Dave, I’m assuming one lead from the volt meter to that wire you’re talking about, and one lead to ground?

[BeerBudgetRacing]

If the alternator runs through the master switch, check it to see if it's actually switching on.

[David Ferguson]

Dave, I’m assuming one lead from the volt meter to that wire you’re talking about, and one lead to ground?

Yes, that's correct. I would also check the resistance (ohms reading), between the alternator body and chasisis ground (alternator does not have to be turning). This should be less than 1 ohm. There might be a separate ground wire from the alternator to the engine block since anodized aluminum is not a good electrical conductor. But if one of the alternator mounts bolts directly to the engine block, you are probably OK. Ohmmeter will confirm.

[Extreme1]

Ok thanks guys. I’m out of town, I’ll check everything when I get back. I’ll keep you updated. Thanks again everyone.

[kflyer]

On the back of the alternator where the single wire that has the female spade connector attaches there are TWO male terminals. If you are not attached to the correct terminal it will not charge. Connect to the other and check for charge. -Kevin

[Fred Michael]

On the back of the alternator where the single wire that has the female spade connector attaches there are TWO male terminals. If you are not attached to the correct terminal it will not charge. Connect to the other and check for charge. -Kevin

If you are connected to the wrong terminal the engine most likely will not shut off with the switch

[Extreme1]

////Update/////

First I wiggled the spade connector ( there’s only one ) on the back of the alternator, and checked the tightness of the ring terminal connection. Then I started up the car and after a few minutes, revved it to 4000 RPM, then connected a voltmeter lead to the big terminal on the back of the alternator, and the other lead to ground. The voltmeter was reading 12.7 volts at idle. The dash was showing 12.4 volts.

Should it be reading higher or is that okay at idle? Should I get my wife to sit in the car and rev it higher to see if the voltage output increases? Any other thoughts?

It has a double pulley system and both belts were turning like they should be. There was no belt slipping.

[Extreme1]

Yes, that's correct. I would also check the resistance (ohms reading), between the alternator body and chasisis ground (alternator does not have to be turning). This should be less than 1 ohm. There might be a separate ground wire from the alternator to the engine block since anodized aluminum is not a good electrical conductor. But if one of the alternator mounts bolts directly to the engine block, you are probably OK. Ohmmeter will confirm.

Hi Dave,
I checked the resistance using my Fluke. It showed .6 ohms resistance from the body of the alternator to the engine mounting bolt.

Sound okay?

Mike

[Extreme1]

/////Another Update///////

Maris stopped by and revved the engine to 4000 rpm and held it there. I checked the voltage coming from the big lead off the alternator . The most it was putting out was 12.8 volts.

Im thinking it should be higher, correct? Normally car alternators are 13.8-14.3 volts.

[Extreme1]

Finally fixed!!!

I took my existing alternator out of the car and to an alternator shop. He bench tested it in front of me and it tested good. I watched when his machine put a load on the alternator and it hit with 50 amps and 14.3 volts of charge. I was stumped and frustrated.

I had already ordered a new alternator. It just arrived, I installed it, and it’s charging at 14.2 volts.

If anyone has a similar problem, just replace the alternator.