Low Beams and Highbeams both went out

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72valiant

72valiant

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Hello, I was driving home from work tonight and noticed my headlights were both out on my '72 Valiant. I wiggled the headlight knob some but it had no effect. I then pushed down on the high beam switch on the floor board. The high beams came on for a split second and then burned out.

Does anyone have any suggestions as to what the cause could be? I've never had both lights go out at once. And I had just replaced one of the bulbs barely a year ago.
 
Do you think the headlights are blown out or should they still be working if it was the dimmer switch? I wish I could fix it now but its almost 1am here and everything's closed plus I have to work in the morning.
 
It's not uncommon for the wiring plug that attaches to the dimmer switch coming loose. I'd try to wiggle/test it to see if the lights come back. I can't imagine your lights actually blowing. There is a headlight breaker that could be an issue but not as likely as that dimmer switch.
 
If you lost both at the same time your probably looking at dimmer switch onfloor or headlight switch itself. The dimmer switch just because of it's location down on the floor is subject to abuse, check first there, pull the carpet back if you have to and make sure the connector is still tight, then if it is check for 12 volts with a meter if you don't have that you may be needing a headlight switch but also first there make sure the connector on the back of it is tight and not come loose
 
The headlights should be OK. It sounds like the dimmer switch is shorting power to ground, that is triggering the self resetting breaker in light switch. The dimmer switch toggles the headlight feed power to high or low beams, and does not involce a ground connection, except for mounting.
 
Hell you can "rig" it on the spot, there are only three wires.

Turn on the light switch, find the 1 of 3 that is hot.

Try it to the other two and find low beams.

Jumper them together and drive home.
 
On a few occasions, we've had a vehicle come in with both headlites burnt out.. We surmised the drivers had been unknowingly driving with one headlite for a while, (like you never see, ha ), when the other goes out, THEN they notice..

And of course you figure,, can't be both seal beams at once,, lol.. so you check all the other stuff,, only to learn to check power to the headlites 1st...

hope it helps
 
This case sounds like the switch but I did buy a 73 Satellite years ago and the low beams didn't work so I checked the switch. It was fine. Yup both low beams were burned out...DOH!
 
It's also possible you have a charging problem, the voltage "went high" and burned out the lamps, but usually, I would expect OTHER problems related to the high voltage
 
If a bad dimmer switch send both high and low beam current for extended period could that blow the bulbs ? I really don't know ?
 
RedFish said:
If a bad dimmer switch send both high and low beam current for extended period could that blow the bulbs ? I really don't know ?
Click to expand...

no, you can run a light with both high and low beam on at the same time... it is a lot of current draw on the system but won't kill the lights.... (done it on purpose before, using relays though)
 
Most every modern car with the light and dimmer switch on the stalk on the steerin column burns both high and low when you pull back on the switch to flash somebody. You are burning both when you do that.
 
Yes, but that is for a limited time. I have "heard" also, that extended running with both beams in the low beam lamp will shorten it's life. "I should try it" LOL
 
Well, I tried to replace the dimmer switch before work this morning but stupid Autozone has the wrong switch listed as belonging to the '72 Valiant. I'm gonna track down the correct one tomorrow once I wake up.

After having spent the day thinking about it I remember having a strange power surge in the car about a month ago. It was daylight and raining outside. All of a sudden my wiper blades started moving back and forth and a very accelerated pace. I quickly turned them off. The next day I replaced the voltage regulator and every things seemed fine since then. Now I'm wondering if that surge burnt my headlights out and I'm just now noticing it.
 
Well, did you actually check this out or are you just throwing parts at it?
 
What are you talking about?

I've worked 24 hours in the past two days. I've made my situation very clear in my post. I have tomorrow off and I will be able to get a good look at it then.
 
I had a similar thing happen tonight with my 67 Dart about a mile out of town and noticed my low beams going out just for a split second, stopped for ice cream, got to the edge of town, then the low beams would go out for a full second or so, tail lights were still working, ended up driving home with the high beams. Thoughts? I had a 72 Fury that the headlights would go out ended up changing both the headlight, switch and dimmer but it was so long ago that I don't remember which one fixed it.
No pictures of low beams, please.
sorry, don't mean to hijack the thread.
 
If it was me, I'd apply voltage to the headlight wires exiting the bulkhead in the engine compartment. That will give you an idea if the issue is upstream (pass compartment) or downstream (engine side) from the bulkhead.
 
Think I fixed my lowbeams. Pulled the carpet up and the plug was loose on the dimmer, and the black wire was coming out of the socket, then one prong broke on the dimmer switch. Went out to my favorite parts car(78 Dodge Sportsman motorhome)pulled the dimmer out and also took the molded plug as it has a base that gets screwed down under the dimmer so the plug cannot work loose unless the screws come out. Also trimmed some of the padding on the Dart carpet around the dimmer and made the dimmer hole bigger as the dimmer was hanging up on the grommet. Sorry I was going to right down the numbers on the motorhome dimmer plug and forgot. I think it is fixed but it seems like sometimes lighting gremlins just pretend to be fixed only to pop up at the worst times.
 
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