headlight problem.

[MIDNIGHT RIDER]

Headlight mod? I have a similar problem. Only my brights work, I click it into low beams and the headlights turn off. Sorry I cant help, but maybe its the same problem.

You have either a bad dimmer-switch; or, more likely, both head-lights are shot on DIM.

When one bulb shoots an element, whether Bright or Dim, the other bulb will soon shoot on account of it now getting all of the power.

 

[redneckaggie]

Sorry i never followed up on this thread it actually ended up bein a bad fuse. The filament inside the fuse was just barely cracked and not burnt at all and it looked good and tested good maybe because when i would push on the fuse it would actually close the break in the filament. i went ahead and replaced the fuse and everything is perfectly fine. thank you for the in depth explanation on relays though that will come in handy when working through a future problem. when i understand how something works it always helps to figure out why it malfunctioned.


but while we are on the subject are there any other headlight bulb options besides the normal halogens. something like the cool blue or whatever those lights that look blue but are bright as hell.

 

[MIDNIGHT RIDER]

but while we are on the subject are there any other headlight bulb options besides the normal halogens. something like the cool blue or whatever those lights that look blue but are bright as hell.

So far as sealed-beams go, Sylvania makes a couple notches above the run-of-the-mill halogens, Xtra-Vision and SilverStar.

I had SilverStars on two of our trucks and we could see plumb across the county............., so long as they were working.

With a good strong relayed system, the SilverStars don't live long; and, almost as soon as one bulb shoots, the other follows suit.

At twenty-bucks plus each, this soon gets expensive; so, I down-graded to the plain old halogens; they are still plenty bright, just not the pavement burners that the SilverStars are.



Kits are available to changeover to the "European" system of permanent lens and all manner of little fragile replacement bulbs, including those blue ones; but, such tom-foolery doesn't appeal to me; I very much prefer sealed-beams.

 

[Greenie]

I finally fingered out my problem (with low beams, that is) the truck has a Fisher plow and there are two relays added to the truck's wiring. One or both relays are bad.

 

[jim x 3]

When one bulb shoots an element, whether Bright or Dim, the other bulb will soon shoot on account of it now getting all of the power.

Midnite:

If you have used large supply wire to your headlight lamps when you did the relay mod, then your analysis of failure isn't quite correct. Lamp resistance is the power limiting factor, so the remaining lamp won't consume any more power.

But if you replaced both lamps at the same time, if one is at end-of-life the other is likely near end-of-life as well.

Regards,

 

[MIDNIGHT RIDER]

Midnite:

If you have used large supply wire to your headlight lamps when you did the relay mod, then your analysis of failure isn't quite correct. Lamp resistance is the power limiting factor, so the remaining lamp won't consume any more power.

But if you replaced both lamps at the same time, if one is at end-of-life the other is likely near end-of-life as well.

Regards,

My analysis is correct according to the experiences we were having.

All head-light wires are 12-AWG, including GROUNDs and new replacement pigtail-sockets that also have 12-AWG leads.

I can install TWO NEW SilverStars; a couple months later, ONE will shoot; SECONDs later, DUE TO NOW RECEIVING ALL OF THE AVAILABLE POWER, the other will also shoot.

Regardless of whether they shoot on BRIGHT or DIM, it usually takes out both elements of the shooting bulb.

Have you ever noticed that, when meeting an oncoming vehicle that only has one light burning that the remaining light blinds you more than the same vehicle would with both lights working ??

The same principle applies here; one light shoots = the other one is now receiving ALL the current that was being shared by both.

The same principle is exhibited when we change from the wimpy factory system to larger wires and a much shorter path from source to light via relays.

Before the change to a relayed system, voltage AT THE BULB, lights ON and engine running , depending on how healthy otherwise the factory system is, will be somewhere between 9-volts to about 10.5-volts.

Bigger wire and a shorter path via the relayed system will yield within 1/4-volt of full regulated alternator out-put, depending on vehicle = between 14- and 14.8-volts.


Regardless of how much power a lamp "consumes", it can only "consume" the power available to it.

For instance, one marker-light is going to be a lot brighter than a whole string of them on the same circuit.

The same principle is exhibited when you start turning on accessories.

Nothing ON but the head-lights and they will be as bright as the system allows; start turning on wipers, blower, more lights, and the coffee-maker, and the lights will dim ( and other accessories slow ) with each added load, due to decreasing available power with each added load.





For what it's worth, since we down-graded to plain old halogens, although not nearly so bright, the bulbs are lasting much much longer.

 

[Greenie]

I finally fingered out my problem (with low beams, that is) the truck has a Fisher plow and there are two relays added to the truck's wiring. One or both relays are bad.

Just in case someone has a similar problem, there are 2 relays - both identical laid in the cavity under the drivers side battery. Carquest gets $14 each for them. I replaced the 2 in 20 minutes and am golden again.

 

[rjjp]

but while we are on the subject are there any other headlight bulb options besides the normal halogens. something like the cool blue or whatever those lights that look blue but are bright as hell.

Yes, go to your local wally world or meijer or even the car parts store and you can find them for your 91, 9007 is the bulb type your looking for.

 

[redneckaggie]

thank you i notice you have plenty of parts trucks any chance you have a steering column for an 87-91 truck

 

[OLDBULL8]

In the first place you shouldn't even have a fuse in the headlight circuit.

The headlight circuit power should be direct from the battery or any hot point connection with the key on thru a CIRCUIT BREAKER of suitable size. When you do the mod for the power to the relay. If a fuse blows, LIGHTS OUT no see where your going. Thru a circuit breaker, the breaker will continuosly reset it self. The lights will go OFF/ON/OFF/ON, but you will know there is a problem, all vehicles are wired that way from the factory.

The newer cars/trucks are a little different, where the lights stay on after the key is shut off, but that is controlled by the computer, but the power still goes thru a circuit breaker.

Most all vehicals have the circuit breaker incorporated right in the headlight switch. That's usually what burns up the switch when to many lights are added just to the switch, rather than powering the extra lights thru a relay.

 

[RLDSL]

If you ever need to replace the relays, use these puppies they are waterproof , perfect for mounting under the hood.
I just replaced one of those funky non standard relays that corroded out from moisture that came with the LMC headlight mod kit with one of those . It's nice to have my low beams back.