Topic: Headlights going on and off

[ChrisV289]

Does anyone know what would cause the headlights to go on and off on a 65 fastback?  I was driving home saturday night and the headlights and maybe eventhe fog lights would go on and off.  I changed the headlight switch last year thinking that was the problem since it happened last year as well...I am not sure if the tail lights are going out as well.  Thoughts?

[carlite65]

the headlight switch would be my first check. just because it was recently replaced does not mean it cannot go bad again.then the dimmer switch. i would also check the grounds and connections on those systems.

[gjz30075]

Agree on the headlight switch.  If you put in Halogens of any sorts, the switch won't last long.

[CharlesTurner]

I'd also add that you might have a voltage regulator problem.  The reproduction VR's are notorious for causing problems with light flicker.  Try a Motorcraft electronic voltage regulator.

Otherwise, check all your grounds.

[67gta289]

+1 on the switch

A contact inside overheats and opens the circuit, shutting the lights off.  Then with no current flow, it eventually cools off enough to close the circuit, turning the lights back on.  The process repeats itself.   This is how the turn signal and hazard light blinking mechanisms work, although by design as opposed to what you are dealing with for headlights.

I've had one fail even with the standard (non halogen) lights.

If you need the halogens or other higher load bulb set, you should either install an interposing relay or, better yet, find out if someone makes a repop with a higher current capacity.  The relay is more involved and is an extra device that could fail and result in no headlights.  Also if you modify any circuit carefully consider the power source and fuse/fuse link size - we don't want to melt any insulation and start a fire.

[Richard P.]

It does sound like you've got a bad headlamp switch. As mentioned earlier if you're using Halogen bulbs they draw more current than regular bulbs. I've solved that problem by installing a 1969 Mustang headlamp switch. The 1969 Mustang came with four headlamps and the headlamp switch has a larger resistor to carry the current. You'll need to remove the bracket from the back of the old switch and install you old bracket on the new switch. I've had luck super gluing the bracket back on. Be careful with the super glue and don't get it inside of the switch as it will stick everything inside the new switch together.

[Texas Swede]

I did exactly the same as Richard on my 67 Shelby over in Sweden.
Used a 69 Mustang switch for 4 head lamps and glued the bracket onto
the new switch. Many years ago I was driving back to our summer house and it was very dark outside. Suddenly the lights went off and when they came back on a few
seconds later a large moose was standing in the middle of the road too close for comfort.
Slammed the brakes and was able to avoid the large animal. After that I replaced the switch and have not had any problems.
Texas Swede

[ChrisV289]

Thanks everyone..I am just running regular bulbs as opposed to halogens...Does anyone know what the main difference is between the three headligh switches that they offer?  They have one before 08/17/64, one between 08/17/64 and 11/1964 and then one after 11/1964 to work till 1968?  Of course my car was built on 10/29/64 so it has that middle switch...Did they try testing something and it didn't work? 

[baflstangobx]

I have to disagree with the use of a '69 switch.  It is designed for a four-lamp system and will not work properly with any other.  I do however use a '70 switch with good results.  Just drill out the bracket spot welds and JB weld the early bracket onto the '70 switch.  I had a '70 box that contained a '69 switch and it had many problems until I saw the engineering number and realized it was boxed wrong.  The 65-68 switches have an internal circuit breaker for the headlamps and it is a lesser rating than the '70 ( 20 amp as opposed to 30 amp I believe).  That will typically correct the problem with halogens.  I know you said that you were not running halogens so I would venture that the culprit may be the dimmer switch.  It is often overlooked but can cause the exact situation you are experiencing.
Bill

[Richard P.]

I've only had and used the 69 Ford Mustang head lamp switch on my wife's 65 convertible for 20 years. I guess I haven't waited long enough for it to fail. I'll wait a little longer and see what happens. 

[ChrisV289]

Still working on finding the problem.  I am working on trying to find a headlight dimmer switch made here in the USA.  I did look at the olde dimmer switch and it is the original switch with the Fomoco script on one of the prongs.  I do have a question, does anyone know what the main difference is between the three headlight switches that they offer?  They have one before 08/17/64, one between 08/17/64 and 11/1964 and then one after 11/1964 to work till 1968.  Of course my car was built on 10/29/64 so it has that middle switch...Is there a real difference between the three?

[baflstangobx]

The early switch is for generator equipped cars.  The last is a replacement for the middle and I do not know what the running change was.  More than likely a small change at best.  Did not last long.  Have you checked with your local Ford dealer.  They had gotten rather expensive but I thought they were still available.

[NEFaurora]

It's most likely a bad headlight switch or a bad ground contact.. It's usually not much else.

Tony K.