Help! Ford F53 Alternator Over Voltage

[Tom N3EQF]

2015 Windsport on 2014 Ford F53 chassis - V10. Engine starts normally, but voltage on the chassis runs 17 volts DC, dashboard goes dead in a moment, except for the battery idiot light.

Chassis battery is good. In fact, it was the original battery so I replaced it with a new one just in case. Problem remains.

I removed the alternator lead from the battery positive post. Now, the dashboard stays up but the battery light remains. I am not surprised at that, since without the alternator charging the battery the voltage soon falls below 12 volts.

I'm assuming the voltage regulator is internal to the alternator. What has me really puzzled is that when I measure the alternator lead (still removed from the battery) with respect to ground, I measure ZERO volts! I was expecting to see a high 17 volts on that lead, which to me would for certain that the alternator is bad.

Does anyone have suggestions? I have a trip to NASCAR races in Darlington at the end of the week, so I am in a panic! No way my battery will last an 8 hour trip without the alternator charging it.

[javelin]

Sounds like a bad regulator and it is likely built into the alternator as most modern units seem to do.....it conveniently costs more to replace things, coincidently.

Before you do the alt replace though, I would suggest making sure all your battery cables at the chassis battery and the alternator are clean and tight; all ground cables as well; and that any other connectors on alternator are also in good condition and tightly connected. It might also be worth checking for computer codes on your OBD2 plug as I am not sure if PCMs these days also have some control over charging systems......it would not surprise me; but I am not sure either. Perhaps others with past V10 charging problems can comment as well?

[ducksface]

https://js-alternators.com

Not the help you want, but if you need to replace it, you might as well go to 370amp....

[Tom N3EQF]

Originally Posted by javelin

Sounds like a bad regulator and it is likely built into the alternator as most modern units seem to do.....it conveniently costs more to replace things, coincidently.

Before you do the alt replace though, I would suggest making sure all your battery cables at the chassis battery and the alternator are clean and tight; all ground cables as well; and that any other connectors on alternator are also in good condition and tightly connected. It might also be worth checking for computer codes on your OBD2 plug as I am not sure if PCMs these days also have some control over charging systems......it would not surprise me; but I am not sure either. Perhaps others with past V10 charging problems can comment as well?

Thanks for the good reply. I just got back from the RV and checked the wiring just as you suggested. No issues found. I have a monitor plugged into the OBD2 plug full time, but it only displays "connecting..." so that appears to be inop as well.

I'll be reaching out to local mobile RV techs in the morning and hope that one can come out and work a miracle so the DW and I don't miss the races!

[javelin]

OBD2 plug needs power to handshake with the code tester/monitor device ....so ignition on.....maybe you have a fuse(s) blown or other battery fault somewhere also affecting your OBD2 monitor interface?

[16ACE27]

You will get nothing out of the alternator without the battery connected. It needs some voltage to generate the field in the rotor.

[rynosback]

Originally Posted by javelin

Sounds like a bad regulator and it is likely built into the alternator as most modern units seem to do.....it conveniently costs more to replace things, coincidently.

Before you do the alt replace though, I would suggest making sure all your battery cables at the chassis battery and the alternator are clean and tight; all ground cables as well; and that any other connectors on alternator are also in good condition and tightly connected. It might also be worth checking for computer codes on your OBD2 plug as I am not sure if PCMs these days also have some control over charging systems......it would not surprise me; but I am not sure either. Perhaps others with past V10 charging problems can comment as well?

Connections should be fine as he was seeing 17 volts.

[rynosback]

Originally Posted by Tom N3EQF

Thanks for the good reply. I just got back from the RV and checked the wiring just as you suggested. No issues found. I have a monitor plugged into the OBD2 plug full time, but it only displays "connecting..." so that appears to be inop as well.

I'll be reaching out to local mobile RV techs in the morning and hope that one can come out and work a miracle so the DW and I don't miss the races!

Replace the alternator, as they all have the regulator built in now. You also may want to retest your new batter after replacing it. As an over charging alternator can damage your battery.

[ducksface]

3. Upgrade your alternator wiring.

Do this too while you're torn down.
I don't have a clue as to a Ford v10, but it makes a very obvious difference in incandescent lights and the sound of the horn on a gm vehicle.

Big three is universally accepted as having value.

[Tom N3EQF]

Originally Posted by 16ACE27

You will get nothing out of the alternator without the battery connected. It needs some voltage to generate the field in the rotor.

DING DING DING DING! That was the correct answer! :-) In the heat of battle I overlooked that possibility. I was expecting the excitation voltage would be supplied by one of the other leads on the alternator connector, but indeed the main lead to the battery was needed for the alternator to create output.

Bottom line, my alternator is now replaced and all is well! Thank you all for the helpful suggestions. We'll be off to NASCAR races at the "Track Too Tough to Tame!" soon.

Oh, one other item. The ScanGauge plugged into the OBD2 port is toast. I tried it in another vehicle with a different cable with the same endless "connecting..." result. I like ScanGauge so I'll buy a new one.