Headlight fuse pops when I "get on it"

Anyone had this problem? Headlights are fine when driving "normal" but lay into it and your in the dark! Makes for an exiting ride, that's for sure. Never had a problem with this before. Just installed a new set of 34 commercial headlights from Speedway. Both are grounded to the frame and are currently wired up on high beam only. Any thoughts would be helpful, thanks.

 

That's a good gas saving device.....

 

Wow, I am looking forward to seeing the answer to this one
I can't really wrap my head around it being a voltage / rpm type problem.
I think you may have some wires grounding out behind the light possibly or another short that is ready to ground at any time and when you drop the hammer the wiring is moving slightly and grounding out then.

 

Finish wiring them and see if there's any difference. Not likely, but have it 100% before you start chasing ghosts.

Popping a fuse USUALLY indicates too much draw (amperage) on the circuit. Can't see how getting on it (higher RPM therefore more potential for alternator output) would create more demand on the fuse.....

Wait, how are they wired? Heavy duty or new headlight switch involved? That could be faulty, but I'm troubleshooting something I can't see.

Sent from atop my toilet using the TJJ app for Android.

 

High beam only? Like Daddio said, finish wiring then trouble shoot.

 

CHECK THE CHARGING. Quickest and easiest thing to do.

 

trace the wires out, it sounds like a wire is pinched or pulled during body roll/twist.

 

does it blow in nuetral while reving it up?Why are the high beams just wired up?

 

Did you size the fuse correctly for the high beams? They're normally higher wattage and draw more current.

 

I'm thinking the regulator sensing wire isn't seeing the correct voltage and over compensating with over voltage. As others have said hook up a volt meter and try to reproduce the problem.

 

Higher voltage would draw less current....if the fuse is blowing, the voltage would likely be dipping down, drawing more current.

 

I'd run the harness thru a wiggle test

 

True only if the resistance changes. While a headlight resistance does vary slightly, I'm 99.5% certain that if you bump up the voltage across a headlight filament, you will also see a rise in current.

To the OP, it does sound like you have a wire that is moving under acceleration. Could be a headlight wire, if you have an alternator with a remote sensing lead, that lead could be losing it's connection and going open, which would result in the alternator output voltage increasing, and a corresponding current increase through the fuse. Albeit for a short time. No pun intended.

 

Could be a problem with your flux capacitor back feeding through the electrical system. Does it only happen when you hit 88 MPH?

 

I experienced a similar problem with my old 4 door Deuce,,I was running down the interstate running with traffic and suddenly no lights....

I had blown a fuse,I road down the shoulder for about a mile and eased into a well lit gas station and got under the dash to discover a blown fuse.

I bought a couple,installed one and flipped the headlights on.. everything worked as it should and I hit the interstate not having any problem until I pulled off the highway and meandered the dark back roads leading home,,I tapped the dimmer switch and the lights went out.

A few days later I started looking for a short and couldn't find one,,I convinced myself it was it was the dimmer switch and replaced it,,sitting in the shop I cranked the car,turned on the lights,hit the dimmer switch both high and low beams worked flawlessly and I patted myself on the back as I had solved the problem.

By this time daylight savings time had started and I was usually home before I need the headlights...but one evening it started raining and I flipped on the lights and every thing worked as it should then about 2 miles form my destination all of a sudden no lights!

I didn't try to find the problem that evening but within a few days I stuck a new bigger fuse in thinking the previous one was to small,,hit the lights and everything worked as it should,,I drove the car around in the daylight with the lights for most of the day on bright and on the way home I noticed the hi beam indicator light was out.

By now I had just about wore out my tester but upon return arrival to the shop out it came again,,this time I found my problem,,it was my headlight switch,,I removed it was shocked to see that the phenolic material on the top of this particular headlight switch had deteriorated and cracked and obviously when I hit a bump it would ground out.

I replaced it and never had a problem again. HRP

 

Why would you be driving at night with high beam only? If you met me at night with high beams on you can expect a rock through your windshield.

I had a Caddy that rubbed through the loom cover and the breaker would pop when I hit a bump. It's easier to find at night as it sparks.

 

A circuit breaker would be a plus in some of the scenarios offered above, many later model (60s and up..maybe earlier?) OE switches have them built-in, and CBs can be had for fuse slots as well.

 

If they are aimed correctly(down and to the right), you'd never know they were high beams.

 

Obviously,you don't have a car with small bulb headlights,,the early cars with a glass lens and small bulbs on high beam are marginal at best.

They don't even begin to compere with normal seal beam lights and pale in comparison to the extra bright blue lights that are common on todays autos. HRP

 

Thanks for all the replies. Getting ready to head out to the garage and have a look at things. To answer a few of your questions, they are wired up on high beam only because I've never had a dimmer switch on the car. The old headlights were wired this way and I ran it for 7 years and never had a problem, also never had anyone bright light me. Also noticed that my new engine seems to have separated the rubber from the metal part of my motor mount (ain't torque great!) So my engine got quite a lean last night. So guess I'll switch over to some all metal motor mounts. She's not really built for comfort anyway. I guess I could run more wires (to try and hide) and put in some sort of dimmer switch, but it had always done fine without one up to this point without. Going to check my grounds and pull my headlight switch out to check next, updates to follow...

 

Uhhhh........then, functionally, that would make them LOW beams, would it not?

 

I'm going to guess that Hot Rod Primer has this one nailed! I have had a similar situation with the Plymouth at one time. With non relayed headlights on the car and running my high beams most of the time back in the sealed beam days I would find the regular Cole Hersey switches would last about two years and that was it. I have since gone to a set of Hella flat lens Hallogen headlights with high output European spec bulbs, (the human smuggling types have a bad habit of driving loaded trucks down the opposing left lane with no lights to avoid border patrol stations on highway 8!) and relays so the switch doesn't take the entire load of the headlight out put.

Barring that I would check regulator function as everybody else said.

 

Ehh, just brighter low beams

 

Sounds like you have a overcharging issue. Are you running a genny or an alt. If genny, what is the condition of your Voltage regulator? Is the cut out circuit operating correctly??? Do you have an ammeter, if so what is it telling you? Or is it as simple as pinching a wire into a direct to ground short during engine movement?

 

I think if there is a fully charged battery in the system it would be able to supply MANY amps ( a couple of hundred) with minimal voltage drop ( 1 or 2, or maybe 10.5-ish) for several seconds, just like it has to starting my car on a frosty morning. Look what a pair of batteries can do @ 4:00 here -
http://www.youtube.com/watch?feature=endscreen&NR=1&v=PV5oLPLUzrM

DC test - Hook a 6 volt incandescent stop light bulb to the terminals of a 6 volt battery with an ammeter in the line, and a volt meter across the bat terminals. Read and record amps and volts. Then repeat with a 12 v battery. Quickly read and record amps and volts.

AC test - Rewire a 120 volt test receptacle adapter as 240 volts. Set up video camera. Borrow your neighbor's pride and joy expensive 120 volt shop vac, and Plug in to 240 volts. Post video on You-tube.

 

I am leaning toward 2 possibilities...

HRP thing..... and perhaps at higher speeds, or when you hammer it, the engine leans, or fan blows just enough causing a wire to ground, thus popping the fuse...

I would even check wires near the throttle linkage under the dash

 

The headlights in question

The plot thickens, here is the headlight switch which has a 30amp fuse which has NOT blown, the fuse in the fusebox (which calls for a 20amp) is the fuse that has blown, even tried a 25 with the same result. However it's only the headlights that are affected, taillight does fine. I switched headlights/taillight/and engine over the winter. The fusebox came out of a 76 Pontiac if I remember correctly. I am running an alternator also. alternator is just a standard GM, not a one wire unit.

 

Also installed a battery quick disconnect this winter, but don't see how this would affect anything.

 

Forgive me if I'm wrong, I'm no electrician, but I did stay in a holiday inn last night... I don't know if my thought process is correct but hear me out.. More voltage causes a light to be brighter, reason being is the filament is being stretched causing more resistance, more heat, equals more current/amps. Am I wrong? I always like to learn something new....

 

So I dug out the old headlights and they only had one wire coming out. If this is the hot wire how are these grounded? the new headlights have 3 wires, one ground, one high beam one low beam. I wired the old "hot" wire to the green high beam wire and ran the ground wire to the frame.