Bitsyncmaster
08-03-2026, 09:13 AM
I ran this alternator diode test on my car. I have a DMCH alternator that provides over 14.5 volts engine running at 850 RPM no loads. Testing the voltage at the cigarette lighter.
You want to have your electrical system loaded to detect a bad diode using an AC voltmeter. Note my idle RPM is 950 with the AC on
Headlights on, I have LED headlights
Defogger on
AC on
Blower #4
DC voltage = 13.95 volts
AC voltage = 0.083 volts
If you have a bad diode in your alternator, you AC volts will be much higher.
Would be nice to have some other owners share their results.
You want to have your electrical system loaded to detect a bad diode using an AC voltmeter. Note my idle RPM is 950 with the AC on
Headlights on, I have LED headlights
Defogger on
AC on
Blower #4
DC voltage = 13.95 volts
AC voltage = 0.083 volts
If you have a bad diode in your alternator, you AC volts will be much higher.
Would be nice to have some other owners share their results.