72 c10, my headlights only works on high beam. Does any one have experience with this problem.. I've already replaced dimmer switch, waiting on head light harness to come in to change that.. any suggestions ???
this is a straight forward system....headlight switch sends power down the yellow or probably BLUE wire to the center terminal on the dimmer switch... the dimmer switch sends the power to either right or left terminal.. there is NO OFF Position..from there it will be either a TAN wire or a LIGHT GREEN wire... HIGH and LOW beams..the third wire on the back of the bulbs is a ground connection to the engine core support..don't forget...from the NEGATIVE BATTERY terminal.. you have to have a battery cable to the engine blockfrom the negative battery terminal.. you have to have a smaller wire to the radiator core support...from the back of the engine.. you have to have a ground wire to the firewall.. take a look at how they run the grounds on a later GM truck..can you figure out which wire is the ground connection.. twist the end of a long wire around the terminal coming out the headlight.. that plugs into the black wire in the socket.. then touch that to the negative battery and see if the headlight comes on when you operate the dimmer switch to both positions..you could also have an issue with the bulk head connector..i am really familiar with this models headlights and turn signal lights..i just finished making a 71 GMC lights system work..when i got there.. the tech had all the bulbs hanging out of their housings.. the ground wires for the headlights were connected.. but the ground between the negative battery and the body was missing as was the ground between the back of the engine and the firewall..he could not figure out why the turn signals did not work as all the bulbs were hooked up.. and had just cut the turn signal switch harness to replace the ts switch... the turn signal bulbs ground thru the housings... and the housings have to be grounded thru the body/chassis... all the way back to the battery negative...do you own a digital volt meter.. print this chart.. follow it .. run the tests.. post results by number1....2...3.,..4....i drop in here a few time a day... so feel free to ask questions... i even have a wiring diagram sitting in front of me to help..
THANKS FOR THE INSIGHT. THE PASSENGER SIDE LIGHT WAS WORKING, & THE DRIVER SIDE WAS OUT WHEN I BOUGHT THE TRUCK. SO I DECIDED TO UPGRADE WITH THE SILVER STAR LIGHTS.. THEY WORKED FOR A FEW MINUTES AND STOPPED WORKING, SO THAT WHERE I'M AT NOW CHECKING THE WIRING..
start with a test light at the dimmer switch...yellow or blue wire... to the Center terminal should have power when you turn the headlight switch on..clicking the dimmer switch should switch the power between either of the outer contacts.. like i said. there is NO off position...only issue might be is if the wiring got reversed on the dimmer switch... if the power from the headlight switch is run to one of the outer terminals on the dimmer switch.. it will only connect to one contact...this is the back of the connector.. the top single terminal is from the headlight switch...the lower TWO are high and low beam...i don't recall which one of the terminals on the headlight bulb is ground.. its either the left or the right. but looking at which end.. front of back.. this is an issue with my brain.. why i cannot recall..again.. one of the three will have power when the dimmer switch is in one direction.. depress it and the other will have power.. you will have to follow the 3 wires to figure out which one is ground... just be sure that you understand that electrons flow from NEGATIVE to POSITIVE...so .. no ground.. no electrons to flow and heat up the element to turn on the light.. even though the head light might come on dim.. it might be getting ground the hard way thru the other bulb..
THANKS FOR THE INFO ..