Wow, you got to love this group. 10 or so responses on headlight issues.
However, no one answered my question as to where the headlight relay is and
if the headlight switch has a circuit breaker builit in as in some
vehicles.

Snoman, I checked the voltage at the battery with the engine running at
around 2500 rpm and got 13.5 volts which I believe is normal charging
voltage. Please correct me if I am wrong. I then changed both bulbs and
everything works, that is both high and low beams now work. Conclusion:
Both bulbs did in fact fail at around the same time. I will/ or my son will
now "Drive happy". Thanks to all who responded. By the way, the comments
posted caused me to re-think electrical circuits and I now realize that a
short circuit would not cause the headlights to fail. Only an over
voltage/regulator problem would do that. However, one final question: If
this vehicle has a headlight relay, (which I can not seem to find), and I
think it must, to avoid heavy wires to the lights and a heavy duty headlight
switch, and if the relay shorted, would that cause the headlights to fail?
I am thinking that if so, then the high beams would fail also. Just
wondering, as the problem seems to be fixed for now.

"sf/gf" <sf90006 (AT) kart (DOT) com> wrote


You are correct. The actual number is 13.6, but close enough ...




I then changed both bulbs and
If the relay shorted ON, the lights would remain ON. If the relay coil
opened, then the relay would not fire and the lights would remain off.




You're way over thinking this. The easiest solution is always the most
likely problem. If the easy stuff doesn't work, THEN put on the Thinking Cap
and analyze stuff until smoke pours out of your ears.

On Mon, 21 May 2007 00:59:08 GMT, "Jeff Strickland"
<crwlr (AT) verizon (DOT) net> wrote:


Actually there is no exact voltage because it will vary with
tempature. It could be as high as 14.5 in cold weather and as low as
13.2 or so in hot weather. Typically it should be in a 13.4 to 13.8
range with a warm engine after running for a bit. When you start
seeing voltages of 14.0 and above when warmed up, you may have
regulator issues because a atlernator can produce well over 16 volts
when regulator goes bad.
-----------------
TheSnoMan.com

"sf/gf" <sf90006 (AT) kart (DOT) com> wrote

If by "fail" you mean "burn out" then the answer is heck no. People are
infatuated with short circuits, so when I am troublshooting, I like tok say
that it's already as shorted out as it's going to get. A headlamp takes
full voltage on one side and a complete short to ground on the other side.
When it's working, it's as shorted out as it can be. No matter how much
stuff shorts out on the truck, you won't generate any extra voltage with
which to burn out light bulbs. I hope this makes sense.

I am innocent on the thermal overload and relay questions, since I don't
have the same kind of truck. I can guess the answers, but I'm not going to
guess. That's how disinformation gets going in these groups. I can say
this: I have not seen a car with a headlight relay in a long time. I had a
50 Chevy that had one. I think that's the last time I saw one. I have
never seen a car that did NOT have a thermal overload on the headlights, but
that's not something that I routinely look for on a car.