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Old 02-07-2010, 11:04 PM
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High Beams go out!!!!!

I have a 68 Firebird.
124K miles
New headlight control switch on the dash.
New High/Low beam foot switch.
4 new headlights.

While driving at night when I switch on the High Beams they go out totally after about a mile or 2. All 4 beams. BLACK!

I switch to the Low Beams and they come on fine

I must have a loose connection??


Open to suggestions.

Thanks, Gman

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Old 02-07-2010, 11:35 PM
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Check the highbeam switch. I had the same problem and it was a bad switch. I know you said it was new, but with some of the off shore stuff, its really junk. Could also be a ground or a bad headlight switch. The switches are cheap enough.

Do you still have the old ones? If so, you may want to swap them out to check them.
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Old 02-08-2010, 06:18 AM
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As already stated possibly a bad switch,but I would go with the bad ground theory. I have done a lot of electrical and when something makes no sense it is usually a bad ground. It is a good idea to go over all your grounds while you are at it. Grounds are just as important as hots.My friend had a similar problem on his 68 Elky and it was the ground strap from the valve cover to the firewall.
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Old 02-08-2010, 06:33 AM
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3 grounds. Back of passenger side head to firewall, neg. post to frame or alt. bracket, and neg. post to passenger side fender where the wheel well meets, or on the front wall next to the radiator by the inside of the headlight where the wires go through to the headlight. Like others said, don't rule out a defective headlight switch on the floor.
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Old 02-08-2010, 10:03 AM
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I had the same problem on my 58 apache truck new headlight switch and new halogen bulbs.The problem is the headlight switch will only handle the amps of the old style headlights.The halogens draw allot more amps.I used 2 relays on the core support by the existing wires.I cut the wire to each headlight and connected them to the relays.The switch only works the relays.One for the high beams and one for the low beams.Use 12 gauge wire to feed power to the headlight relays.
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Old 02-08-2010, 10:35 AM
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first test:
is it the negative circuit side ground source volts/amps supply to the lamps problem tripping the safety breaker = just run a jumper connected to the wire lamps ground connect screws to the batt neg post,,,,motor off/high beam lamps on and stay on with the jumper = neg ground side needs attention...
(a smart move is make the jumper a permanent ground wire for a "belt and suspenders" worth of conductor path even if the ground is now OK,,,very often that copper ground to the batt will make lamps brighter because the positive ("wire") side of the circuit does degrade)

second test:
is it high amps "heat" tripping the breaker on the positive side of the circuit (due to a bad switch or bad wire or corroded firewall connect etc)=do a voltage drop test with a meter = motor off,,,lamps off,,,measure the volts across the batt terminals,,,then,,,lamps on measure the volts at the lamps to see how much was lost in the circuit...

lamp Watts= Volts x Amps
55 Watts lamp with normal 12V supply at the lamp = 4.5A worth of heat in the wire
55 Watt with only 9 Volts at the lamp = 6.1 amps "when cold" and more amps when/as all gets hotter to the point it trips the breaker to prevent a electrical wire fire....

test shows say 12.4V at the batt and say 12.0V at the lamps (typical on a old car) it is OK and the dimmer switch is likely the fault source

can just be a corroded lamp plug in female socket at the lamps on the high beam post,,,that plug is not sealed and is exposed to water and air which with a current present causes rapid corrosion...

Last edited by red65mustang; 02-08-2010 at 12:36 PM.
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Old 02-08-2010, 10:36 AM
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I was also going to suggest the circuit breaker in the headlight switch, but if you immediately switch back to low beams, do the lights go on? If so, it is probably not the switch since it does take some time to reset the breaker as it cools.

The low beams use the same ground as the high beam filaments in those bulbs, so again, if the low beams work, it is unlikely to be these grounds. It IS possible that the ground between the core support and the rest of the body is bad.

There is no relay in the headlight circuit of your car. My thought is also with the dimmer switch.
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Old 02-08-2010, 12:04 PM
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The dimmer is most likely overheating and the contacts are failing. In order to find out what the issue is you need a meter or a test light. You can then methodically start following the circuit to see where you are loosing the connection. Like the others have posted, It sound like your dimmer switch but I dont replace anything unless I know it is bad.
Are the lights you are running standard seal beams, if not some of the newer style bulbs draw a lot more current and you may need to install a relay with the proper current rating to run the lights.
The first thing is find out where it is failing and go from there.
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Old 02-08-2010, 03:10 PM
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Change the dimmer switch. Well most of the time thats what is wrong also check the wires at the dimmer switch.


Last edited by eloc431962; 02-08-2010 at 03:16 PM.
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Old 02-08-2010, 03:35 PM
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I'd first double check the wire and terminals to the floor dimmer. A new switch can be bad, but those old wires/terminals are really suspect in this case, IMHO.
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Old 02-08-2010, 05:24 PM
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Brighter Headlights>> http://www.madelectrical.com/electri...adlights.shtml
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