Headlights intermittently turning off and on.

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Location
Blue Springs, MO
My Car
1971 Mach 1, Grabber Blue w/Argent stripes. Original 2V 351C Auto, Tilt, rear defog, Black Comfortweave Interior. Under restoration. Original colors, 4V 351C, 4-Speed, Spoilers, Magnums, Ram Air. All Ford parts.
Has anyone ever solved this problem? I thought I had the solution, but I am stumped as the problem is still here.

When driving with the headlights on, the headlights will turn off and come back on intermittently. Some seems to be vibration related, but It does it at stops too. High beam or low beam. It did it before restoration, and it is doing it now even with harnesses checked by Midlife, NOS headlamp Switch, new dimmer switch, and a headlamp relay kit from CJ Ponyparts. I am afraid something is heating up and I am going to burn the car up or something.

I thought the problem was the headlamp switch, so that was replaced first. then I added the relay system since I was running halogen headlamps. Now that I am finally doing some dusk and dark driving, I am shocked to see the problem is still there. I thought the ONLY thing I had not replaced was the dimmer switch. Now that I have done that the problem is still present.

What solution have others found?

kcmash
 
I would have suggested a loose ground or balky headlamp switch, but you seem to have those covered. If you think you have a thermal problem, you can check for warmer than normal harnesses with the lights on and the car stopped. There are cooling sprays used to check electronics for thermal intermittents - you can try spraying the connectors to see if there is a resistive pin somewhere. Do the lights turn off intermittently with the car just sitting still with the engine off?
 
The usual solution for Halogen headlights is a relay. Is the relay you installed rated high enough for the current load? I'd recommend 30-40 amps as a safety amount.
 
Ok I just did a garage test. Yes I have a relay system. It has a 30 amp fuse in the power line. When I shook that around the lights come on and off. I am VERY unimpressed with the fit of the fuse. It was quite warm when I pulled it out, and the fit is very loose. The fuse never”snaps” in place.

So this appears to be a very cheap way to build the fuse box on the relay system. The whole thing was under $100. So I am thinking of getting a better fuse holder and splicing that in unless Midlife feels I am safer buying a higher end relay kit. Attached is the picture of the one I bought and have in the car now.

Kcmash
 

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I purchased that same relay harness and the fuse blew after using it for an hour or so. I replaced that fuse with another spade type fuse after pinching the contacts inside the boot to ensure good contact. No problems since then, but if it happens again I’ll go the circuit breaker route mentioned by Hemikiller.
 
So I just pinched the contacts on mine. That was definitely the problem based on the charring on the fuse terminal. Anyway I increased my pullout force for the fuse by 4x easily. I tried shaking the fuse holder severely and had no intermittent lighting. Hopefully that keeps the contacts tight and the heat at the fse down.

thanks for the help everyone. I noticed this problem is a frequent complaint on the CJ Ponyparts site for this product.

kcmash
 
Rocketman may have a relay system (RCCI). He's one of the forum sponsors and his work can be trusted.
I totally agree re: his headlight relay kits, and to the comment that his work can be trusted. We are fortunate to have him in our forum, much less in our particular hobby.
 
Simply replace the fuse with a circuit breaker. You want a Type 1, which automatically resets regardless of the load being present. Image from the Bussman catalog.

View attachment 78488
Nice photo and info. I felt it was well worth saving the photo and part #s in a PDF file for future reference. Thank for sharing it.
 
So I just pinched the contacts on mine. That was definitely the problem based on the charring on the fuse terminal. Anyway I increased my pullout force for the fuse by 4x easily. I tried shaking the fuse holder severely and had no intermittent lighting. Hopefully that keeps the contacts tight and the heat at the fse down.

thanks for the help everyone. I noticed this problem is a frequent complaint on the CJ Ponyparts site for this product.

kcmash
Thank you for sharing what you found. Too often such questions are not updated with the final correction needed. Frankly, that is probably one of the last things i would have considered looking at. Well, no longer. It will now be one of my first checkpoints.
 
So I just pinched the contacts on mine. That was definitely the problem based on the charring on the fuse terminal. Anyway I increased my pullout force for the fuse by 4x easily. I tried shaking the fuse holder severely and had no intermittent lighting. Hopefully that keeps the contacts tight and the heat at the fse down.

thanks for the help everyone. I noticed this problem is a frequent complaint on the CJ Ponyparts site for this product.

kcmash
Out of morbid curiosity I thought I would check the reviews of this product. Most of the ratings were positive, every positive. Bur, sure enough, there were several low ratings that all involved a loose fuse holder issue. I hope the manufacturer takes the time to read the ratings and does something to correct that design issue.

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I did not buy a kit. I used 14 Awg GXL High Temp Automotive wire and wired my own adding to the factory wire harness when I repaired and rewrapped it. Taped into the factory high & low beam wires to term 86 on each 40 amp SPDT relay and from the battery to the high and low relays term 30 and 87 NO to the headlights. Connect 85 to chassis ground. I had to buy a pair of 3 terminal ceramic headlight plugs. No more stress on the old headlight and high beam switches.

I also recommend doing the same for the two horns to take the stress off the horn pad in the steering wheel. Especially on a rim blow. The horns draw a lot of juice.
 
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