generator testing - looking for confirmation and suggestions
Thread Starter
Pro
Joined: Mar 2001
Posts: 675
Likes: 0
From: formerly perryth TX
Cruise-In VIII Veteran
generator testing - looking for confirmation and suggestions
The last few times I went to fire up the 62 it needed a battery charge if it had been more than about 5 days. I went three weeks without trying to start and it was completely dead. So new battery is in tonight. With the car running there is only about 12.4 across the terminals.
Im suspicious of the generator so to test I got my voltmeter, attached black to field, red to arm, and with the engine running it reads a little over 10. Shouldnt it be higher and did I do the test correctly?
Assuming I did and its the generator, any suggestions on what may be wrong?
TIA,
-TP
Im suspicious of the generator so to test I got my voltmeter, attached black to field, red to arm, and with the engine running it reads a little over 10. Shouldnt it be higher and did I do the test correctly?
Assuming I did and its the generator, any suggestions on what may be wrong?
TIA,
-TP
Burning Brakes
Joined: Oct 2004
Posts: 1,210
Likes: 1
From: fighter pilots make movies, bomber pilots make history
Todd,
Generators do not put out voltage at idle like newer alternators. My manual for our old 61/62s says at 1500 rpms, the voltage should read 14V.
If the voltage does not increase at 1500, probably volatge regulator...hot, old springs, etc. You can pull the cover and you probably have an adjustment screw since yours is highly original. Requires only a slight adjustment.
Joe
Generators do not put out voltage at idle like newer alternators. My manual for our old 61/62s says at 1500 rpms, the voltage should read 14V.
If the voltage does not increase at 1500, probably volatge regulator...hot, old springs, etc. You can pull the cover and you probably have an adjustment screw since yours is highly original. Requires only a slight adjustment.
Joe
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
On generator systems the voltage regulator can charge continuously if stuck and cause the generator armature to "throw solder" by overheating. If the voltage regulator is doing this, it will quickly burn a new replacement generator out too. If and only if this is the case, a silver line will form inside the generator housing visable at the rear. It may be hard to see with the unit still on the car. But it is a place to check.
Burning Brakes
Joined: Feb 2004
Posts: 924
Likes: 2
From: Kearneysville West Virginia
As a general rule, generators will runs as motors if they are good. One quick and dirty acid test to see if a generator is good, is to disconnect all wires and the fan belt. Then, ground the field terminal and connect a wire from the positive side of the 12V battery to the terminal where the heavy red wire was attached to the generator. If the generator is good, it should run slowly as a motor. Again, make sure all other wires are disconnected and the fan belt is off the generator pulley. This will not work for alternators.
