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Discussion Starter · #1 ·
I must start by saying I'm very green at trouble shooting wiring issues. So here is the problem. Headlights worked a week ago, out now. Taillights, parking lights etc all work. High and Low beams both out. Checked fuses and changed the one I thought was associated with headlights (upper right in fuse box?) Tough to read labelling. Fuse looked bad. No change in light function. What should I do/check next? Never had headlight issues before. Will say that last time I was driving(Sunday) car my foot caught part of wiring under dash above gas pedal( I know secure wires) and stereo (not factory stereo) cut out and back in. Is there a ground under the dash that would impact headlights? Can't be certain this was the cause as it was daylight out. Headlights did not work when went to put the car back in the garage that evening.
 

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Headlights do not have a fuse. Their form of circuit protection is a thermo circuit breaker within the headlight switch that will open up the headlight circuit if a defective headlight or a short is detected. Since a wiring short generates heat within the wiring from overcurrent it will then automatically reset once the heat has been reduced. So in theory the headlights will keep flashing on and off until the problem is resolved. The tail lights keep working since they operate off a different circuit than the headlights but are still controlled by the switch.
But... in your case the switch may have permanently opened up for no reason at all or detected a short and permanently opened rather than resetting.

Another cause could be the floor mounted dimmer switch which receives power from the headlight switch and depending upon its position sends power to either the high or low beams.

For effective troubleshooting you need a test light or a multimeter. Test light is cheap and will do the job. A multimeter is a bit more expensive but also checks AC & DC voltages, circuit resistance, and amperage readings, hence the name 'Multi'. A good tool to have in your box.

All the vendors carry headlight and dimmer switches but you should see what the problem is first before spending your money. So when you have either a light or meter let us know and one of us will walk you through the process.

The only wiring I'm aware above the gas pedal is the transmission downshift switch and of course an aftermarket stereo. but who knows what's under a dash after 49 years.
 

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time for a quality dimmer switch x2
is where I would start
or tinker with it and jump the plug or test for power in and out of switch
 

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Discussion Starter · #4 ·
thank you, appreciate the help. I will post again when I get a test light/multimeter. Hopefully this weekend.
Kurt
 

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Discussion Starter · #6 ·
Hi, finally was able to get the Pontiac out of storage and into the garage at home to work on headlight issue. I replaced both the dash mounted headlight switch and the floor mounted dimmer switch. As a reminder all headlights (low and high beams were out) but all other lights work. After just replacing the dash headlight switch both the high and low beams work together, however I could not get the low beams to work alone. I then replaced the floor mounted dimmer and had the same exact results just all four lights work when the dimmer switch is on high beam setting but toggle it to the low beam position and none of the headlights work. I really could use some help here. Thought I had it taken care of..
 

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Discussion Starter · #8 ·
Thanks for the response. Just so I'm understanding correctly and that I was clear all 4 beams work when the high setting on dimmer switch (dash red light on indicating high beams). I did notice that when I stepped on the dimmer switch to go from high to low beams there is a noise on the motor side of the fire wall, like some kind of relay or something. I do not hear it when high beam setting is on. Here is pic of all four beams. Do the low beam lights have two bulbs? If so then maybe blew the low bulbs when the switch failed?
pontiac lights.jpg
 

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Discussion Starter · #9 ·
Again I'm so green at this stuff. Went back into the garage and noticed that with dimmer switch set to low beams there is a definite noise coming from engine side of mid firewall. Also notice all the other lights (parking, interior etc) are flickering a tiny bit when the low beam setting is on. This does not occur when high beams are on. Wondering if there is some kind of relay bad or maybe the dimmer switch pigtail connector? Attached pic of new dimmer switch with old connector. I'm completely guessing. Thanks for any help!
pontiac dimmer switch.jpg
 

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Discussion Starter · #10 ·
Going to borrow a multi-meter from a buddy this weekend. I noticed that it looks like previous owner by-passed the tan wire to the dimmer switch(can see in pick above. Worked with no issues for 6 years for me). I've not had time to trace out the dark green wire that seems to by-pass the tan. The blue goes to the headlight switch. I'm guessing the tan should have been the low beam wire before they by-passed. Does anyone know? Love this wiring stuff😆
 

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Green - Hi Beam
Tan - Low Beam

Previous owner may have added relays to the headlight circuit and the low beam relay could have failed.

835734C4-4F46-4CA3-92E3-8AAD5A6C41A3_1_105_c.jpeg
 

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Discussion Starter · #12 ·
71 wiring.jpg
Confirmed that it is tan wire(low beam) that was by-passed in pic from earlier post and dark green (not the light green hi beam wire) used to by-pass is actually tucked behind bolt that mounts power brake booster(my finger is touching before it passes behind bolt)that was installed at a repair shop last year. I think they must have accidentally pinched the wire and now the wire insulation has been worn through and causing a short? I bought a circuit tester today and will see if the original tan wire has power to end that is cut. I suspect not and reason for the dark green by-pass. Seems like I should just place a new wire from the dimmer pigtail connector to the place the dark green was spliced back in at the front of the headlight harness (haven't found yet but will). Am I missing something here?
 

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I think you're on the right track. Sometime in the past, the tan wire was bypassed with a new jumper which is now open.
And now would be a great time to upgrade the headlight wiring from the dimmer to the headlights and add some relays.
Factory wiring was small (16 gauge) and just barely met specifications. I upgraded mine with 14 gauge. Where the wiring runs through the firewall plug is very easy to replace. The larger Packard 59 Terminals for the headlights are available from Texas Industrial Electric. I got the correct colored wire from M & H. This is one of the easier electrical mods to do since the wiring is out in the open.



or you can buy the forward lighting harness for about $225
 
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