Head lights Flashing

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mchandford

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May 23, 2012
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Location
Marysville, WA
My Car
'71 Mustang Mach 1 "M" Code. 351C and 4 speed toploader.
I had posted a question a while back and got responses about my headlights turning on and off while driving. So I have already replaced the headlight switch. That was quite some time ago and I haven't really had it out at night since. Well, i went out to dinner with the car this last weekend and the lights started flickering on and off while cruising around the parking lot. I am not sure if they will keep flashing with the car at higher RPMs. Maybe that will answer some questions about it though. I am thinking it is in the lights themselves, but then it is both of them at the same time, not alternating. So it must be in the fuse box, or in the wiring somewhere. Any thoughts on how to track this down? Preferably without tearing out all the wiring and starting over. Maybe a wire is too small gauge and needs to be replaced? a bad connector somewhere? or maybe just a bad fuse. i wills tart with the easy stuff and go from there, but wanted to ask all of your thoughts first.

 
A common problem, almost always found with a faulty dimmer switch. It has too much resistance and is causing the headlight switch to activate its internal circuit breaker which causes the headlights to turn on/off in a cyclic manner. Replace the dimmer switch and all will be right with the world.

 
A common problem, almost always found with a faulty dimmer switch. It has too much resistance and is causing the headlight switch to activate its internal circuit breaker which causes the headlights to turn on/off in a cyclic manner. Replace the dimmer switch and all will be right with the world.
HMMM. even if I already did that?

 
Did you install a relay with the new switch back then? Will the switch turning hot if "on"?

A common problem on the older circuits is, that in the light switch there is a bi-metal as a overcurrent protection! Now, if the current is too large due to stronger lights or if the contacts of the bi-metal due to resistance (old contacts) are too warm, then the light suddenly drops out ... and comes sometime shortly thereafter!

The best remedy is to light via a relay (normally 12V/25Ah you get it from a car parts dealer). So the light switch only has to turn the small control current. Then the switch will no longer be warm and the lights do not turn on and off.

Here is a small instruction which you can zoom in:

http://tinypic.com/r/34f3q/5

Hope, this helps,

Cheers

Tim

 
A common problem, almost always found with a faulty dimmer switch. It has too much resistance and is causing the headlight switch to activate its internal circuit breaker which causes the headlights to turn on/off in a cyclic manner. Replace the dimmer switch and all will be right with the world.
HMMM. even if I already did that?
Are you running Halogen headlights by any chance? They use more current than the wiring was designed for. If not, then you have high resistance in the headlight circuitry, probably in the headlight harness under the hood.

Headlights (and dash lights) can "flicker" or change intensity with a bad voltage regulator at near curb idle rpms, but that isn't quite what was described in the first post.

 
A common problem, almost always found with a faulty dimmer switch. It has too much resistance and is causing the headlight switch to activate its internal circuit breaker which causes the headlights to turn on/off in a cyclic manner. Replace the dimmer switch and all will be right with the world.
HMMM. even if I already did that?
Are you running Halogen headlights by any chance? They use more current than the wiring was designed for. If not, then you have high resistance in the headlight circuitry, probably in the headlight harness under the hood.

Headlights (and dash lights) can "flicker" or change intensity with a bad voltage regulator at near curb idle rpms, but that isn't quite what was described in the first post.
the headlights do flicker a little bit at idle. And I think they are halogens. So how can I get less current without losing out on brightness? Thay are already pretty dim to begin with. i think i may upgrade to the newer bulb housing and replaceable bulbs. What do you think?

I also like the idea of the relay in-line. I will do some more research on that and see what I come up with. I will have to find the headlight wires in the engine bay first.

 
Any resistance in the system can contribute to the headlight switch circuit breaker acting like this. Tylicay bad, worn-out dimmer and/or headlight switches can do this, as can bad grounds and degraded wiring.

Go through and methodically clean every electrical connection and your problem will probably cease.

 
Do you have original wiring or aftermarket? some aftermarket harness' do not have heavy enough wire, so they use relays that kick out when hot...otherwise midlife has got you covered

 
I had posted a question a while back and got responses about my headlights turning on and off while driving.
I had a similar issue 5 years ago. Was stuck 40 miles from home without headlights. It ended up being the HIGH BEAM foot switch. Got one at Auto Zone for $10.

Kick the switch from side to side, should be able to get it to stay on, then off.

Even if that isn't the problem, would not be a bad idea to replace it.

 
I remember when I had the same problem I replaced the headlight switch and it got worse. I guess some of the new made in China reproduction switches are even more sensitive than my old worn one.

So it might not actually help to change that, although it should be the remedy.

Then there's the high beam switch which can decide from one moment to the next that you don't need headlights right now and turn them off. Like Wolverine said, slightly tipping it from side to side will often turn them on again.

The best remedy is the relay solution. It also made my headlights a little brighter probably because it bypasses a lot of the resistance in the old wiring.

I'd still replace the high beam switch though as it is prone to cause trouble sooner or later.

 
I remember when I had the same problem I replaced the headlight switch and it got worse. I guess some of the new made in China reproduction switches are even more sensitive than my old worn one.

So it might not actually help to change that, although it should be the remedy.

Then there's the high beam switch which can decide from one moment to the next that you don't need headlights right now and turn them off. Like Wolverine said, slightly tipping it from side to side will often turn them on again.

The best remedy is the relay solution. It also made my headlights a little brighter probably because it bypasses a lot of the resistance in the old wiring.

I'd still replace the high beam switch though as it is prone to cause trouble sooner or later.
If your looking for a relay kit to bypass the headlight switch then you may want to check out Rocketman's offerings.....

http://rccinnovations.com/index.php?show=menu-hrk-all

BDK

 
Ok...I traded messages with Rocketman after watching the video above and bought the kit. It fit like a champ, and is totally concealed. I won't know for sure until I drive it a few times at night but so far all looks good!

John

 
Ok...I traded messages with Rocketman after watching the video above and bought the kit. It fit like a champ, and is totally concealed. I won't know for sure until I drive it a few times at night but so far all looks good!

John
Curious to see how you like the kit. I bought it too but haven't gotten to the point of installing it yet. I want to use halogen lights so this seemed to be the route to go. Been happy with everything that I have purchased from Rocketman.

 
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