The Stovebolt Site Forums The Shop Area The Electrical Bay Hi beam problem

I recently replaced beat up wiring harness on my 58' apache with a wiring harness from a classic truck vendor. Since then, the Hi-beams will turn on just fine for about 10 seconds then flicker for a second or two then turn off completely. I don't remember trying the Hi-beams before the rewire as I had just purchased the truck from the previous owner. The re-wire was pretty basic, vendor provided a detailed diagram. I have replaced the dimmer switch and headlamp switch. Low beams function as they should. Anyone have an idea as to why it might be happening?

Chava's 58,

You haven't' said a fuse is blowing and being replaced, so it sounds like a thermal switch is overloading and opening, then cooling and allowing the procedure to repeat itself. Is this what's happening.

While I'm just guessing at this, some light switches have thermal overloads built into them. Maybe you replaced the light switch, but have not repaired the short that is tripping the thermal.

Because it doesn't appear to instantaneous, and it's only in the Hi-beam circuit, it sounds like a wire that is mashed between body panels or something of that sort, a high resistance short to ground.

If any of this sounds plausible, I would inspect the wiring harness that goes all the way from light switch to dimmer to headlights.

EDIT. Did your new wiring setup have a fuse box with circuit breakers?

Stuart

If you have changed to halagen bulbs it is probably drawing more current then the breaker Stuart talks cabout can handle. I would put relays on both high & low beam lights. You would be surprized how much brighter the lights will be. The relays are available as a kit or you can make them up yourself. Headlights going off on a dark night on a country road can be scary.

Here is the write up on Bosch Relays that works for our old trucks. This is posted on Jolly's 60-66 GMC page.

http://www.6066gmcguy.org/BoschRelay.htm

Jake Groby

Automarc, Wrenchbender & V-6 Fix,

I did a complete look-over this weekend. I could not find any spots where the wiring may have been cut up or shorted out. I replaced the dimmer switch as these are easier to come by. Same result. The relay suggestion is the next up for me. I'm unfamiliar with relays and will hve to study up on V-6s relay page before I tackle it. I keep thinking that the problm has to be somewhere between the dimmer switch and the high beams themselves, am I right to think so?

Chava,

The question that needs to be answered first is...when the high beams flicker and turn OFF, what does it take to get them back ON.

Are you having to replace a fuse? If you don't have to replace a fuse and they will function again after sitting awhile, you are dealing with some type of thermal overload.

If it's a thermal overload, and it was purposefully installed in the circuit by someone, then the first step would be to see what its electrical rating is and to see if you could step up a size or two to match the current draw of your high beams.

Do you have to replace a fuse or not..that's the big question!

Stuart

LMC has a kit with relays, connectors, & directions for about $30. You can hardly buy the parts for that.

The Hi-Beams will turn on and work for about 15 seconds, then begin to flicker, turn off, flicker some more, turn off again, flicker again and so on. Once I push the dimmer switch to Lo-Beams, the low beams work just fine. Then I push the dimmer switch again to high beam, they will work for a little while and begin the flickering and shutting off routine.

Chava,

This is strange. I looked at some '58's in the gallery and they appear to have four headlights. I'm not familiar with these rigs so I don't know if HI beam is all four lamps illuminated, or if there are two dedicated HI beam lamps only.

What I'm driving at is, is it possible to swap the circuits to see if the problems follows the physical wiring when you stick it on the other headlights.

For the HI beams to flicker and go out, the circuit (or ground) must be interrupted. Then for it to go back on, the circuit must be made again. If there is no thermal circuit breaker or switch in the circuit, it would leave only a faulty wire or faulty connection. A loose connection on the HI beam circuit might work when cold, then as it's powered, the heat builds resistance and the circuit fails. When it cools, it works again.

This makes sense to me, but then a lot of things make sense to me...I would look for a loose connection or even a fault in the wire the HI beams. Has it been determined that the headlight switch itself doesn't have a thermal strip for headlight overload protection.

If you can isolate a single wire for that circuit, you would 'jump around' it with a temporary wire from dimmer to some terminal strip on a inner fender or something.

Having the HI beams turn on and turn off like they do screams loose connection to me!

Stuart

the 58 is indeed 4 eyed
the low beams are the outer pair
the high beams should be all 4 [same bulb #s]
there is a thermal protection circuit on the light switch

in a quiet place, engine off, turn the headlights on, click to high beam, listen carefully for any click noise from the switch

could be a poor connection heating up, which could be the socket that plugs onto the bulbs - if so, you might see some evidence there in the form of melting plastic

Bill

Bill,

We have been waiting for you and your TF expertise!
Stuart

I will look at take another look at the headlight switch and the wiring coming in from the inner fender to the headlight socket. As both headlight are flickering and turning off simultaneously, am I right to think that the glitch would be after the dimmer switch to the headlights?

The glitch could be anywhere in the circuit. I noticed on your first post that this was after a conversion to a new wiring harness. Did everything work o.k. before? Did you change out the light switch or is it the original one?

My thought, for whatever it's worth, is this sounds to me like a breaker that possibly came with the new harness that's not rated high enough for all those filliments up front. Take a look at the schematic that (hopefully) came with your new wiring and see if it uses circuit breakers and what they are rated for. It may be as simple as changing out a breaker.

Chava,

If LO beam is the two outside lights and HI beam is all the lights, what lights flicker and go out on HI? If there was a thermal overload located in the headlight switch, ALL the lights would flicker and go out.

When the lights are on HI beam, and all the lamps are illuminated as Bill in indicates, and the problem happens, do just the inside lights flicker and go out? This would mean it is indeed in the circuit from dimmer to headlights...wouldn't it!

Does this make sense?

Stuart

As I recall on my ol'59 the outside lights were dual filament (hi/lo) and the inside lights were single filament (high only). They are 2 completely independant circuits controlled by the dimmer switch.

Lets say the new wiring harness came with a 15 amp breaker for headlights that is wired through the headlight switch then to the dimmer switch. On low beam, everything is fine. But when the highs are switched on the circuit pulls (lets say) 18 amps. It works for a few seconds, then "poof" no lights. The problem appears to be between the dimmer switch and the headlights as the low beams work fine, but actually the problem is way back behind the dimmer switch. That's why I'm saying the glitch could be anywhere in the circuit.

I was also curious if he replaced the light switch as it may have a thermal protection that is not rated for that much load.

As waldo stated, the 58 does indeed have the single filament headlamps inner, double filament outer. I have looked over the wiring again, checking for any bad grounds or possible cuts in the wiring, with no problems found. I ordered the relay kit from LMC that wrenchbender talked about. I hope to get it in the first part of next week. I am anxious to see the difference in terms of light brightness that the relays might provide. I will let you all know how it goes. I am a little confused as to the "breaker" that is being mentioned. Are you referring to the fuse that is on the dimmer switch? If the fuse failed, wouldn't the lights no longer turn on at all?

Chava,

The pregnant question with this whole thread has been the suggestion that the lights flicker and go out when switched to HI, then after a period of time seem to auto reset and do the whole scenario over again. This isn't the same as blowing a one time fuse that needs to be manually replaced.

A self resetting circuit breaker or a thermal overload will break the circuit under a higher than rated load, then automatically reset the circuit after cooling. This is done with no outside influence from you.

A loose connection could simulate this too. The marginal connection passes current and the circuit functions. Because the connection is loose, it creates heats and eventually opens the circuit. Like the thermal scenario above, it then cools and the circuit closes. This theory is a stretch, but has been know to happen.

The bottom line is this...what is causing your HI beam circuit to flicker and shut down, only to function a little later with no outside influence. That's the million dollar question.

A headlight relay system will not fix this unanswered problem.

Stuart

Many head light switches have a built in thermal breaker. 4 halagen headlights are too much load for this. I think a relay on the high beams will solve the problem.

Sorry, I called a relay a circuit breaker.

I would suggest that you observe the dash lights when this happens. If the dash lights go out, the thermal breaker is indeed tripping. If this is so, it probably will be making a buzzing noise at the same time.

I'm sorry if I caused any confusion or problem on this. I said circuit breaker but meant relay. Old age I guess.

Chava,

Does the Hi-beam indicator in the speedo cluster work? If not, could the lead to this lamp be shorted? It is in the Hi-beam circuit as well as the head lights. Just a thought.

best wishes,

Les

Hey Everyone,

It's finally fixed. I picked up the relay kit from LMC. I noticed that the kit was made in China, so I was a little concerned. I had to make a few alterations to the wiring from the kit, but really no problems, just a little extra time for the install. The relays work beautifully, the lighting is much brighter. I would recommend this upgrade to anyone that drives their stovebolt frequently. Thanks to everyone for the great advice.

Check the point on the headlight switch where the main power is attached. The crimp stud holding the anchor was loose. Found this to be the issue on one truck today. Getting a new switch this week. Danchuks?

I installed the DANCHUK switch, I have cleaned the paint off the small area where each side of the 4 head light system grounds and have daisy-chained this ground back to the horn and battery ground. Still have high beam flickering that still takes out the high beam indicator, dash lights and the low beams. Wiring harness has no pinched points on it anywhere, checked it all out. Alternator puts out around 22 amps (down from 28 amps with old switch) with the high beams on. Delivers 14.4 volts to the battery. 3 amps to the battery.
I am wondering if I have a 'floating' ground point that is causing the high amp draw with high beams on? What is the best way to check out ground points? What makes a good ground? The truck has been totally disassembled, painted and re-assembled. Has the ground straps going to the cab from the frame from the cab to the battery, from the frame to the bed, bed to each tail lamp.

It's the light switch. The switches that are sold do not stand up to the quality of the originals. Do the relay addition and no more problems.
With the relay the load for the lights is carried through the relay not the switch. The only thing the switch does is turn on the relay, which is powered and feeds the lights directly from the battery, thus no big draw on the light switch.
If you look on the old switch, and turn the knob you will see a coiled spring that is the part of the switch that dimms the dash lights. On the left side of the switch is a Bi-metalic arm that heats up and if the amp draw is to much opens the circuit and the lights go off, it cools down and the lights come back on.
When you install the relays the load is through the relays not the switch.

I recently had problems with my headlights going out repeatedly, after replacing the harness with the newer style heavy duty harness anticipating installing the projection style lamps. After buying replacement relays twice from the original vendor, I had a visit with a true parts man who understood how to look something up in the book vs. relying on what he was told by the computer, and buying a pair of B/W #4136 relays.Problem solved. Cost more, but warrantied for life. What I learned is good ain't cheap and cheap ain't good. Driving blind is the pits.

This is a good instructive thread. Thanks to Tommy for explaining soup to nuts what the relays do, and why the old setup wasn't working. If I'm correct the attached link is the relay fix Chava used. Does anyone know if someone makes a harness for modern vehicles/lights that includes this relay setup?

Heavy duty harness

Allen,
The newer vehicles most probably already have relays for the lights. Most of them have the high powered lights, and if you look around under the hood, you will see quite a few relays scattered around. I'm NOT a mechanic and really don't work on or near a new vehicle, just an assumption on my part that they already have relays.

One last word on this from me. When my relays were going bad, I was having to buy replacements from LMC, as nobody could cross reference the oriental part number. Of course, when I ask for a number from the vendor, they won't tell you anything, because then, you'd buy them from someone else. Most of the folks working at the parts stores anymore, don't know anything other than what the computer tells them. Relays were costing $X.00, freight twice that, and they were lasting me about 1 week. The new ones were pricey, but came with a lifetime warranty. Fix it once and be done with it. Just my experience.
Tramp

Thanks Tommy. My post was worded very poorly. What I meant to say, is a harness for us guys restoring these old vehicles with modern parts, like high amp halogen lights that we know will cause a problem with the hi/lo beam switches. Just seems like some of these better end harness makers would include the relays.

Always check your grounds first... bad grounds are the cause of many electrical "night mares".