[Steve's 66 Cat]

I've had issues with my headlights for a while. It seems like with the low beams on, they will light just fine for 15 mins or so of driving and then they will start to flicker on and off without any effect from the road. I can be sitting at a light completely stopped and they will flicker. If I try to run the high beams the problem becomes even worse and they flicker rapidly.

I've tried inspecting and wiggling the harness in the engine bay but found nothing wrong there. I was also messing around with the high beam floor switch and thought that to be causing the problems since I could hit it and move it a little and make the lights flicker. So I replaced the switch but the problem still persists. Anyone else know what I can do?

[Steve's 66 Cat]

I've had issues with my headlights for a while. It seems like with the low beams on, they will light just fine for 15 mins or so of driving and then they will start to flicker on and off without any effect from the road. I can be sitting at a light completely stopped and they will flicker. If I try to run the high beams the problem becomes even worse and they flicker rapidly.

I've tried inspecting and wiggling the harness in the engine bay but found nothing wrong there. I was also messing around with the high beam floor switch and thought that to be causing the problems since I could hit it and move it a little and make the lights flicker. So I replaced the switch but the problem still persists. Anyone else know what I can do?

[66bonneville]

my bonneville did that several years ago. turned out to be the wire that grounds to the firewall, just under the booster. it wasn't off, just loose.

[george kujanski]

Check your grounds at the headlights, make sure the connections to the dimmer switch are clean and tight, all the ground straps are in place connecting the sheet metal to the frame, to the block, etc. and make sure the regulator body is grounded well to the firewall, & firewall to the block.

George

[Steve's 66 Cat]

Thanks George, as you suggested I picked up a copy of the electrical diagram for my car and traced through all of my grounds. I found the two right next to the headlights themselves to be rather weak and not making a good contact. No more flickering lights!

[Steve's 66 Cat]

Alright, my problem continues after fixing grounds and replacing many questionable looking connectors in wire harnesses. I was about ready to give up then I decided to look at the light switch itself behind the dash. Upon inspection, I found that the 7 pin harness is melted in a couple of spots. I also noticed that the switch box itself gets scorching hot in a matter of a few seconds when the lights are turned on. None of the wires are hot until the switch box heats them up. My guess is that something inside is shorting out. Is this a common occurance? I haven't found any of the wire leads on the connector to be shorted anywhere, so that's why I'm now thinking it's the switch. Anyone have input on this?

[george kujanski]

My first thought would be that the connectors are loose; once they get loose, they will get hot, discoloring the plastic connector. Also, once they get hot, the brass terminals tend to lose their spring tension, propagating the problem.

Squeeze the terminals with some long nose pliers and see if the heat problems diminish. If not, there may be the same type of problem internally in the switch. A third possibility is that there is short in the circuits connected to the switch, drawing extra current, but this would tend to blow a fuse.

[Steve's 66 Cat]

Well I did some digging tonight and here's what I found.

-The plastic harness is melted pretty good from the heat off the switch, but it still feels very tight on all the connections.

-The headlight switch heats up within 10sec of turning the lights on and will burn your hand.

-I disconnected the switch and ran 12V straight to just the headlight wire in the harness and was able to switch the lights from low to high and have no flickering, not to mention the lights were extremely bright. This leads me to believe the headlight switch itself is bad.

-I also checked the alternator (brand new one wire delco 12SI) and it seems to be charging a little high at 14.5 - 14.6 Volts. Any ideas about this???

[george kujanski]

You've done some good investigation on the switch problem, Steve. From what you are saying, it sure sounds like there is a high resistance connection in the switch. One other possibility is that you are getting high current draw in your other lighting circuits, i.e. taillights. The switch connects them all together whereas it sounds like in your test, you just connected the headlights. You could try simulating the actual connections, altho at this point, the cost of a switch is not too bad.

The regulator inside the alternator is temperature compensated such that it charges slightly higher when the alternator is cold. Run it awhile with lights on, etc, and then measure, the voltage will drop a few tenths.

Also, in a one-wire configuration, the output voltage purposely may be slightly higher so that at the battery the voltage will be closer to 14.0.

George

[Steve's 66 Cat]

Thanks George, I'll see tomorrow if I can't simulate the entire light circuit with the tails too as a final test. What is my best option for finding a switch? I checked my local parts stores (Napa and Bumper to Bumper) and neither had a listing. I also looked in the full-size PY catalog but they don't show any stock on the 66 switch.

As for the alt, thanks for the info. I didn't notice a huge difference in voltage once the car was warmed up and driven for 10 mins, but I did notice about .2V difference between the alt and the battery, so I think I should be alright.

Thanks a million for helping me out with this tedious problem, I appreciate it since I'm still in the learning process.

[aitstra]

After you get your problem fixed - if you still have dim headlights or your wiring is still getting hot, check out this site. I did the headlight relay thing on my son's old Plymouth and it worked great. I plan to do it on my 68 GTO soon. The guy is great to talk with to on electrical tech for old cars. He has supplies to rebuild harness connectors too.
Brighter headlights -Mad Electrical

Randy

[ctgross]

Steve, I just got a new Year One Cat. and they show the switch for the 64-72 GTO models @ $19.95. Not sure if it's the same for larger cars?