72 Pontiac Headlights

An even longer shot, we had a 65 pontiac ambulance,that would quit,pop it in neutral and it would start again,after many, many garage visits,they put it down to something in the steering mechanism would short it out near the firewall,weird but true...

If you have a wire diagram, find out what feed power to the headlight switch. Check for power there. Just go backwards, till you find out where the power break is. You may need to open up the wire bundles to find a short.

shorts are easy to find just look for the smoke. now a open is the one you have to trace out. the last fuel gage I traced has the short at the clip on the frame. it final cut threw the jacket and ground the wire before it got to the sending unit causing it to read full all the time.

the ignition switches in 68 were the bake o lite back crimped to the pot housing. with contacts in both. we started at the coil and worked threw everything up to the switch and just haven't taken the time to pull it. hard to trace a momentary open. we did the take the cap off and leave it trick first time it happen. the pop right off again and the fact that it's intermittent leads me to the switch being the bad guy. we have a used one we'll try the next time we get the car out of storage

This is directed at John, not to jump the origional poster. My 72 did that several times, but with long periods in between. It would also jerk sometimes, usually after being in heavy traffic. Anyway, shut it off for a long train, and You got it, wouldn't start. A Guy in the club kept telling Me ignition switch. Anyway, sent a Chic to Autozone for an ignition switch, a roll of wire, and some connections. Came back with all. I have a HEI, so I ran a jumper wire from the battery straight to the HEI. Fired right up, made the nite, and drove 75 miles home the next morning. The ign switch #LS309, listed for a 72 Comm chassis. I switched it out, and it worked, BACKWARDS. Turn the key all the way back to start. Anyway, the replacement was made to mount on the pass side of the steering column, not the driver side. Pulled the one off the 72 parts car, and all has been good ever since.

Raymond Armstrong said:

A Guy in the club kept telling Me ignition switch. Anyway, sent a Chic to Autozone for an ignition switch, a roll of wire, and some connections. Came back with all. I have a HEI, so I ran a jumper wire from the battery straight to the HEI. Fired right up, made the nite, and drove 75 miles home the next morning. The ign switch #LS309, listed for a 72 Comm chassis. I switched it out, and it worked, BACKWARDS. Turn the key all the way back to start. Anyway, the replacement was made to mount on the pass side of the steering column, not the driver side. Pulled the one off the 72 parts car, and all has been good ever since.

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Actually the reason the one ignition switch worked backwards because it was the wrong switch. They had two ignition switches for those Cadillac's, one for a non-tilt or telescopic column and one for a tilt and telescopic column. The only difference was that the mounting plates were reversed. The switch its self was the same just the mounting bracket on the switch was turned around. Most professional cars had a strait non tilt column but a few did have tilt and telescopic steering columns. Odds are when asked at the the parts house your girl told them it had a tilt wheel when it was actually a strait steering column car.

69 was the first year for the switch on the column. the 68 down is on the dash. when working on the column mount remember there are two parts the key lock and the switch. the two are only connected with a rod. on the 68 down switch the bake-o-lite works lose from the white metal casting and you can lose contact. that was the lesion from the good old days to not hang all that stuff from the lock. replacing switches under warranty prompted GM to rethink the design for the 69 modal. that must have worked we us it today. the switch is no long available for the 68 down but the key and tumblers are. one way to isolate the open is if the car will start but not run. in this case we have worked over every connection from the coil threw the fire wall up to the back of the switch.so next time we get the chance to bring the car back home we will drop the switch out and check that connector and tighten the back-o-lite on the back of the key housing and hope for the best.

when tracing out the circet the digram is helpful. it lets you see how the major components your having trouble with get and share there power. in the case of this headlight switch and now the gas gage. you know were each thing is in the circet.

the gas gage gets it's power from the battery threw the ignition to the fuse block, threw the gage, threw the sending units resister, then back to ground and back to the battery. in truth all the gas gage is is a volt meter with different markings. if it reds high current it's got a short between it and the sending unit. if it's Reading low it's got a open some were and that can be any were between the positive side of the battery and the negative side. if it reads between it's reading the residence in the sending unit as it should.

it's just human nature to jump in and start taking things apart and replacing stuff. but unless you know were the problem is you never know if your repair was necessary or successful. you may have just created more opens to fix.

my favorite tool for electrical problems are the small amp battery charger and the test light. you can apply power to components to test them and wiring with one. probe to test for power with the other. if the charger finds a short it will hum and not burn up anything. but if the circet from it to the component is good it will work the component. you can eliminate a lot of things with a little power

in my case I jumped for the easy stuff first and was hoping I did not have to go to the obvious and more difficult moving part. plus I was redoing some one else's temporary fix. that switch on the 68 is not a fun one to get out.

Tools

my favorite tool for electrical problems are the small amp battery charger and the test light. you can apply power to components to test them and wiring with one. probe to test for power with the other. if the charger finds a short it will hum and not burn up anything. but if the circet from it to the component is good it will work the component. you can eliminate a lot of things with a little power

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This is one of the best tools for electrical it does it all apply's ground, power , can check for continuity and has a built in circuit breaker and light.

a lot of stuff to buy out there but I all ready have the the battery charger and the test light. 90 bucks will get a lot of stuff.

Update

High beams were still flickering.

After all of the troubleshooting, I think I narrowed it down to a short or overloading in the front headlight harness. Worked on low beams, but would start to click and flicker on high beams. Voltage intermittent at foot switch, which manual confirmed issue.

Bought a front headlight add on harness with relays from eBay. Quality workmanship, ceramic sockets, nice wire with loom and connectors. Plug and play. So far, works like a champ. Highly recommend this for those intimidated by relays.

I can now add my halogen headlights or those dark Louisiana roads, which is how this started in the first place....

Thanks again for all of the tips.