Alternator issues

[Coach_Cleats]

Our alternator is now reading 12 volts. In the past it always read between 13-14.5 volts. Is 12 volts sufficient for battery charging? If not would this be an alternator fail or a voltage regulator problem?

Thanks for your help!

[77rollalong]

check the single large wire coming from the back of the alternator to the isolator to ground (neg terminal) and see what you have for voltage.

[atsrmf]

A 12 volt reading is not charging. Always do the check at the battery posts with the engine running. Minimum should be 12.6, 13.5 to 14 is just about perfect under normal conditions.

[turbojimmy]

wolfe10 wrote:
Stop. You need to diagnose the cause of the "no charge" problem.

Yes, it could the the alternator. But, it could be the BATTERY ISOLATOR.

With a digital voltmeter, locate the battery isolator. Start the engine and use the cruise control to raise RPM to 1100 or so.

Check voltage at the center lug and at each of the outer lugs. Let us know what you get.

^This

A friend of mine went through this over the weekend. Showed up at the campground overheating - battery dead and cooling fans not running. Replaced the battery and alternator on-site. The battery ran itself dead on the way home. The isolator had failed and was not allowing the alternator to charge the chassis battery. Find it and test it before you throw money and parts at it.

[rgatijnet1]

Unless you have disconnected everything from the charging circuit, the 12 volts you are reading is probably your battery voltage, NOT your alternator output.
An OBDII meter can tell if your charging circuit is working. I would suspect that you probably have a failed diode but you also could have an open "exciter" wire if your system requires one. This is a small wire that feeds 12 volts to the alternator.

[wa8yxm]

12 volts is not enough.. However if you changed meters that may be the issue as alternators do not put out DC. they put out rectified 3 phase A/C good chance you've popped a diode or two if you are seeing only 12 volts. An alternator test is often FREE at many shops on a car.. Motor home.. Well may be a big harder to hook up.. Or not. Been a LONG time since I did an alternator test. Pull into "Auto Parts R US" and ask 'em (Generic for most of the low-cost auto parts places) just make sure the store has a big enough lot.

[10forty2]

No, 12 volts is not enough to charge a 12V battery. And yes, it sounds more like your alternator may have gone bad. BUT, not being familiar with the model, there could be a fuse blown in the charging circuit. I'd check for that first, and then consider changing the alternator.

[wolfe10]

Stop. You need to diagnose the cause of the "no charge" problem.

Yes, it could the the alternator. But, it could be the BATTERY ISOLATOR.

With a digital voltmeter, locate the battery isolator. Start the engine and use the cruise control to raise RPM to 1100 or so.

Check voltage at the center lug and at each of the outer lugs. Let us know what you get.

[sailor_lou]

12 VDC is too low. Rather than replacing it with another low quality product I usually bring alternators to a rewind shop for repair. A good shop will repair it better than new for less money with higher quality bearings, a heavy duty diode bank and regulator and will also improve the conformal coating on the windings.

Here is a place I've used that's not too far away from you:

Joe's Auto Electric

I do not work/own this business, just a happy customer. Good luck.

Lou
05 Travel Supreme Envoy

[tinkerer]

My experience with checking voltage on a running alternator reads only 12 volts is not working. That is what happened on my MH. Put a new alternator on and it read 13.6 volts and problem was solved.