Hello all, My 66 is converted to 12 volt. I put a new Bosch, not rebuilt generator in this summer. The battery went dead a week ago and I thought it was because I had left lights on at the store. I took it out and gave it a trickle charge and all was good, for three days. Then last night it wouldn't start, I push started it and drove home. The headights were very dim by the time I got home. The generator is obviously not putting out a charge. What is the method for checking the generator and voltage regulator?
I am better with mechanics than electrical. Any help would be appreciated.
Thanks, Casey
Dead Battery, Generator not charging.
Use a voltmeter for these easy tests:
Battery voltage should be about 12.6 volts with the engine off. Start the engine and rev the volts should increase to about 14 volts and the generator is working and charging the battery. If it does not go that high, check the brushes for wear. With the engine running, push the brushes in a bit with the handle of a plastic screwdriver and see if the volt reading increases. If it does, the brushes may be worn to the point that they don't exert enough pressure on the commentator.
If the brushes are OK, this is the next test:
Remove the wires from the generator. Jumper from the DF post on the generator to the generator frame. Start the engine and measure the voltage from ground to the generator D+ post. Rev the motor and the voltage should go as high at 35 volts as about 3000rpm. If you get around 35, the generator is good. Run this test quickly as not to overheat the generator.
If it fails, the generator may need to be polarized. Leave the jumper wire connected to ground and remove the fan belt. Run a wire from the positive battery post to D+ on the generator. The generator shaft should start to spin. This will properly polarize the generator. If the generator doesn't spin it is bad. If it did spin, put the belt back on and re-test from the top. If you still have low voltage its time for a new generator or take it to an auto electric shop for a rebuild.
One last thing is check the small wire from the generator to the instrument cluster to make sure it is good. Though with a generator it will charge if the wire is bad or bulb is out, it needs to be fixed. BTW, you had an alternator, if the bulb burns out or the wire is bad the alternator quits charging. Just an FYI.
There is a lot of good info on the web about testing the generator. There is also a short YouTube video for testing the voltage regulator.
Battery voltage should be about 12.6 volts with the engine off. Start the engine and rev the volts should increase to about 14 volts and the generator is working and charging the battery. If it does not go that high, check the brushes for wear. With the engine running, push the brushes in a bit with the handle of a plastic screwdriver and see if the volt reading increases. If it does, the brushes may be worn to the point that they don't exert enough pressure on the commentator.
If the brushes are OK, this is the next test:
Remove the wires from the generator. Jumper from the DF post on the generator to the generator frame. Start the engine and measure the voltage from ground to the generator D+ post. Rev the motor and the voltage should go as high at 35 volts as about 3000rpm. If you get around 35, the generator is good. Run this test quickly as not to overheat the generator.
If it fails, the generator may need to be polarized. Leave the jumper wire connected to ground and remove the fan belt. Run a wire from the positive battery post to D+ on the generator. The generator shaft should start to spin. This will properly polarize the generator. If the generator doesn't spin it is bad. If it did spin, put the belt back on and re-test from the top. If you still have low voltage its time for a new generator or take it to an auto electric shop for a rebuild.
One last thing is check the small wire from the generator to the instrument cluster to make sure it is good. Though with a generator it will charge if the wire is bad or bulb is out, it needs to be fixed. BTW, you had an alternator, if the bulb burns out or the wire is bad the alternator quits charging. Just an FYI.
There is a lot of good info on the web about testing the generator. There is also a short YouTube video for testing the voltage regulator.
Hi, thanks for following up. A loose wire in a terminal. New terminal-have charge. I do have a question though - bug is converted to 12 volt and has regulator fastened to the fan shroud. The heavy red wire from harness is connected to D+ and has another heavy wire connecting generator D+ to regulator D+. The thinner wire from harness (generator light)is connected to DF and has a wire connecting to regulator DF. On the regulator I have a thicker wire connecting B+ to starter solenoid. The 61 terminal had a wire that through the firewall and under the back seat that was not connected to anything. My question is shouldn't the thinner wire for the generator light be connected to terminal 61 on regulator instead of DF? Would this be why my generator light was not on when the battery was going dead? It has been this way for the fifteen years I've had the bug. Thanks again for the help, Casey
The wire from 61 should be running to the idiot light. If not, that is why it is not working. Remove it from DF and jumper to 61 and see if light works. You can also just use a test light from 61 to ground and see what you get from there. But yes, the small wire goes from 61 through the harness to the idiot light.
I will lengthen the wire and connect to terminal 61 on regulator. The light comes on when the key is on the "on" position. Explains why it didn't illuminate last week when the battery was going dead. Good thing I have not had a belt break in the last fifteen years! Thanks again for your help and advice, Casey
You may want to check if there is another wire in the loom coming into the engine bay. The wire that runs from the dash back to post 61 is usually in that loom as the voltage regulator was originally mounted on top of the generator and there was not a small wire that ran the path you had mentioned. It may be someone added something over the years and that wire was needed. Good Luck!