headlamp issue

[bornn57]

I have replaced one burned out headlamp and replaced the dimmer switch on my 57 3100. I still am not able to switch from brights to dim or vice versa. Any suggestions?

[mr48chev]

If it has the plug with the three wires going into it that slips on the switch you should be good but if the wires are separate you may have them in the wrong spots so only high or low. I've had to troubleshoot a few done like that in the past

Usually what happens if you are trying to hook up three female slide ends on the switch is that you get the input wire from the headlight switch on one of the output pins and the wire to the light on the input pin so you only have high or low beams working.
Then you have to move the wires around so that they are in the proper spots and you are good to go.

Otherwise it's get out the test light or volt meter and start tracking the voltage down the wires.

[dsraven]

check for proper wire locations on the dimmer switch
check for proper wire locations on the headlights
check for a good ground on the headlights
check for power at the headlights on each circuit

a bad ground at the headlight will give you all sorts of grief. ensure the ground from battery goes to a good ground on the body in several spots, where ever there is a circuit like lights or heater fan etc, that will require a ground.-10ga, frame and engine-battery cable size.

[mr48chev]

I forgot about the ground thing when I answered but about 70 % of the time electrical problems relate directly to ground issues.

[1project2many]

bornn57, why did you replace the dimmer switch?

[mr48chev]

From my experience floor mounted dimmer switches only last about two or three years if you drive the truck regularly. On a Weekend when the sun is shining cruiser they would probably last forever though.

Looking at the stock switch I'd say that two of the wires are in the wrong spot. http://www.oreillyauto.com/site/c/de...1970&ppt=C0039
I didn't think of that earlier thinking that it was the later style switch that sits on top of the floorboard.

[_Ogre]

never had a floor dimmer fail. yet.

first i'd check voltage at the headlights, if both highbeams failed i'd suspect a broken wire
that said... always assume a bad ground on these old trucks

[Jesse Z]

Did he say whether it was a floor dimmer or column? Nor did he say if the high beams worked previously.

Could be a simple short circuit or improper wiring orientation. Here's my hand-scrawled restaurant napkin diagram of GM floor switch wiring position:

[1project2many]

I'm with Ogre. We use a "non-clicking" version of a floor dimmer in some of our school buses to start the yellow warning lights because they last so long.

[dsraven]

hey, bornn57, did you get your lights fixed? if not what have you done to find the problem?

[OrrieG]

[QUOTE=_Ogre;7759003]never had a floor dimmer fail. yet.

/QUOTE]

Agree, I bought my truck in 76 and the original dimmer was still working fine when I took it off in 2000.

[bornn55]

shoulder surgery has put the project on hold i am guessing ground issue. Dim and bright both worked a month ago. It is a floor mounted switch

[dsraven]

I hear you on the shoulder surgery. I just had a major one myself 3 wks ago. debrided acromium bone down till it bled, cleaned up joint cartiledge, 6 anchors placed on humerous, tendons pulled back and attached, muscle sutured together. tylenol is my friend. sleep is just a dream I have. in a sling for 6 wks. hopefully yours is progressing well and you will heal up well. good luck.

if you think you may have a ground issue, you can try turning on the lights and then use a booster cable from battery neg to the rad support, fender mount bolt or headlight ground wire to supply a good ground. if the issue goes away then you know where to start once you can get back to normal.

classic trucks website is a good place to burn some time if you get bored. they have a tech section that can keep your mind busy for a bit and help you pass the time. this site has kept my mind busy for awhile as well.

[Coupeguy2001]

It has been my experience that the headlight connectors by the horns get corroded, and lose contact on one or more terminals.
To keep that from happening, add a little white grease, or some dielectric like dow corning DC-4 compound.