I'm betting that more than one of you will know the answer to my question. The lights on my Skylark - all of them including dash lights - pulsate. The effect is more noticeable at idle than at higher rpms yet the effect remains. The car still has the external voltage regulator. Is this an alternator or a regulator problem? Thanks for the help. Dean
Possibly... I always run my car up to the Zone and have them test the chargins system. Could be voltage reg, or alternator...
Hey Dean, I've been living with this exact problem for about two years now. Both my alt. and reg are about 3 years old. Can you hear the regulator switching on and off in unison with the pulsation? - I can. Are you running an MSD? My dad (a very knowledgable electronics guy) and I have been speculating that without the diode installed with the MSD it causes the pulsation. I've also had some strange battery drawdowns and odd voltage readings that tended to indicate voltage traveling in seemingly impossible pathways (i.e., with the battery ground disconnected why would you find voltage between the battery and the chassis?). I've been too busy to troubleshoot this problem and the car drives fine just the same - just looks lame at night.
In the past when cars I have worked on with that problem, it was either a bad ground from the battery to the frame and body or shorted diodes in the alternator........ You can check them with an ohmeter. Remove the fat red wire from the back of the alt, and check one way-then rerverse the polarity of the ohmeter and re-check. One way should conduct, the opposite way should read infinity. If it reads continuity in both directions, the diodes are toast. If you leave it that way too long, your battery will become toast also.:bglasses:
Thanks for the responses. BTW the car is running a later '70s GM HEI distributor. Will get around to checking with the ohmeter as suggested. Bought the car a few months back and still getting to know it. One thing is for sure, I can assume nothing. This pulsating light thing has got to go before some youngster in his Civic decides my lights are too cool and it becomes another fad. Dean
Joe, My car does not have a ground running direct to the body from the battery. The ground from the engine to the firewall is there and in good condition. In my car's case the pulsation is totally syncronous with the sound of the regulator switching on and off. Can hear it very well since it is on the firewall.
You need to have a ground wire going from the batt. neg. post to the body b/c the neg. cable that's attached to the motor will find ground through your parking cables or whatever path it can find. The motor is insulated by the motor mounts, rear end bushings and exhaust hangers. Trust me on that one, once on a Ford I used to own I melted a new parking cable that way.:af:
Dean, we used to have the same problem with the tanks when I was in the Army. We used to disconnect the negative and still had power on in the tank. Turns out the negative bus bar and cable had welded itself to the battery retainer in a place where it was not easy to find. If theres excessive corrosion, or even moisture on top of the battery, it will cause a battery drain. Cant offer much advice about the pulsing. I use a one wire 100 amp alternator and have had no problems.
Sometime it is the strangest things Had a similar problem with lights flickering bright then dim on Shari's GS on the way back from Bowling Green, KY one year with a fresh rebuilt alternator from Scottys. Replaced the regulator when we got home, but that did not solve the problem. Turned out the connection of the output cable lug to the diode bridge was not clean and tight, therefore eroding the alumnimum away. A fresh rebuild on that alternator cured the problem.
I had an identical problem on my '70 w/ '68 430. I replaced the reg with an aftermarket due to corrosion and the pulsing started. It click in synch with the pulse. I switched to a later internally regulated alt, and soldered jumpers in the old regulator so the wires look correct. No more pulse. it seems the orginal Delco regs varied the field voltage more continuously than the Niehoff did.
I had the same problem. It was high-impedance (bad, corroded, etc.) connection(s). Yours may not just be limited to ground, but could be a weak connection anywhere in the charging loop (including a "bad" ground).
Thanks to all that replied to my question. To all that followed the suggestions this is how it played out. The diodes checked out just fine but the alternator was putting out NOTHING! So I went ahead (apologies to all the concours folks out there) and converted over to an internally regulated alternator and modified the wiring. The pulsating lights are history and my battery can now breathe a sigh of relief. All this also confirmed that the car really needs a new engine wiring harness as the underhood wires, at least, are SOOOOOOOOO brittle from the heat and age. Thanks again for the help. In hindsight I believe the external regulator was the source of the pulsing. Dean
Surprise surprise! My alternator just died. So Dean, what alternator did you buy and did you go to one wire, etc. etc.?
alternator Brad, I switched to the internally regulated type. I got one for a 1974 Regal 455 which is rated at 63 amps. Be sure to save your double pulley for the rebuilt unit will have the pulley for the single belt only. I got mine at the local O'Reilly's with the lifetime warranty and they had 3 units on the shelf. They also had the new plug with the wiring needed to convert to the single wire approach. Got those instructions from some old GSCA newsletter articles. I believe there are instructions from the Buick Performance Group website. Hope this helps. Dean
I've already posted this in another thread, but what you need to do is simply connect the fat red wire to the back of the new alt. and run a jumper from that to pin 2 on the side, that's all there is to it. Your old connector and wiring is no longer needed, unless you wish to hook up your warning light. :bglasses:
