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decco37 · 02-09-2005, 10:48 PM

This one may test you guys to see what we know. I have a 64 tri-power GTO that has a pulse in the lights with the engine running, high or low beam. It's admittedly only a slight pulse, or dimming and brightening, but it'll drive you nuts if you know it's there. I've changed the alternator, regulator, (with new ones), checked the belt for tension, polished all the grounds and their mounting holes, and still can't stop the pulse. No other electrical trouble, starts right up, full batteery all the time, shows 14.5 volts on the volt meter, (aftermarket under dash cluster). Anyone have more ideas as to what can cause this pulse? Thanks for any help.

decco37 · 02-09-2005, 10:48 PM

This one may test you guys to see what we know. I have a 64 tri-power GTO that has a pulse in the lights with the engine running, high or low beam. It's admittedly only a slight pulse, or dimming and brightening, but it'll drive you nuts if you know it's there. I've changed the alternator, regulator, (with new ones), checked the belt for tension, polished all the grounds and their mounting holes, and still can't stop the pulse. No other electrical trouble, starts right up, full batteery all the time, shows 14.5 volts on the volt meter, (aftermarket under dash cluster). Anyone have more ideas as to what can cause this pulse? Thanks for any help.

Pod · 02-10-2005, 04:31 AM

Just an idea, but have you tried swapping the battery?

Droptop64 · 02-10-2005, 11:19 AM

Check the grounds. Even though you may have a ground strap between the body sheetmetal and the engine, it could be corroded/old and not giving the regulator a good solid ground. Is the regulator mount grounded by a wire to the sheetmetal where it mounts?
Actually, the grounding process happens in two links:
1.) from the engine (where the negative battery cable should attach), to the frame.
2.) from the frame to the sheetmetal. Sometimes this second one is done via pigtail directly from the battery post, but on '64s - they normally don't have that provision.
Good Luck...

mike nixon · 02-10-2005, 11:45 AM

if you run the battery down part way does this still happen?

what it sounds like to me is the normal cycling of the regulator with the battery at full charge.

i'll agree with cleaning the grounds. while you're at this make sure the body has a good ground to the frame and the frame has a good ground to the battery.

mike

Pecosbill · 02-10-2005, 01:05 PM

Do you have any non-stock electrical equipment on the car that could be pulling amperage? Our 64 had the same problem and it was driving me nuts. I installed new dash, forward engine and headlamp harnesses, and saw no change (I was going to change these out anyway and was just hoping that would do it). I bought a new voltage regulator and installed it and did notice a little improvement. I then connected another ground wire from the voltage regulator directly to the engine block and the problem ALMOST vanished, but not quite. Shortly after installing the new regulator the idiot light on the dash started glowing and I came to find that the alternator output was down from what it should be. I replaced the alternator with a 60 amp model and the pulsating quit.

loadedgoat65 · 02-10-2005, 07:01 PM

Sounds like possibly a bad diode in the alternator. Are the alternators that you are buying a quallity rebuild? I have seen some cheap rebuilds over the years and with some rebuild companies they will only replace the part that is bad. Only the basics like the brushes or a diode. As long as it passes there bench test thats all there concerned about. As soon as it passes they paint it put it in a box and put it on the self for the next victom. Hope this helps.

decco37 · 02-11-2005, 07:45 PM

I took all the ground straps off and bead blasted them, wire brushed the contact spots, and made sure to get all the grounds. Battery to engine, frame to fenders, engine to firewall, headlights to radiator support, etc. Perhaps it is a diode, or too small an alternator, but I bought a remanufactured alternator from the best parts house in Tucson, so I don't know. How would I check the output of the alternator? Thanks for all youe help, everyone!!! Dave.

george kujanski · 02-11-2005, 08:28 PM

Usually this problem is caused by A poor ground connection from the regulator body to the firewall and back to the battery negative.

Jump the regulator body (a good clean, bare metal spot) to the battery negative while the engine is running. If the problem goes away, the regulator body needs a better ground.

The wirewound resistors on the bottom of the regulaotr need to be riveted well to the reg body also.

George

Tonyc · 02-15-2005, 07:51 AM

I HAD THE SAME PULSING ON MY 64 AND CHANGED EVERYTHING ALSO. BACK IN OCT 2003 CHIEF PONT-YACKER SAID TO CHANGE THE REG.TO A STANDARD MOTOR PRODUCTS PART #VR103. FOR ABOUT 35.00 I DID AND NEVER HAD ANY PROBLEM OR PULSING AGAIN.
HOPE THIS HELPS.
TONYC

decco37 · 02-15-2005, 09:06 AM

I'd lke to thank you guys for your response. I think I found it. The ground from the regulator to the firewall was not good, and I found that one of the wires going into the alternator had a loose connection on the connector. Seems like the problem is solved . Thanks for your help, I knew you guys would find it!!

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