I have discovered that neither of my low beam headlights are working. I tested the plugs for power and I have no voltage. The highbeams and the parking lights are working. I also looked at the relay under the hood in the black box and it appears to be clicking when I turn on the headlight switch. I'm thinking I have a short somewhere but no fuses are blown. Any ideas??
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check low beam fuse when switched on if it has voltage registering across the fuse ,if there is voltage across the low beam RHS fuse then it is possibly a pinched wire from the headlight running back towards inside of the car
ok if you run a power wire to the positive on battery does it go?
if so its a plug or cable issue. if not make an earth wire for the earth side of light and try the power again. if it goes you have a bad earth.
These trucks are known for bad multifuction switches. the switch that i talk of is the signal switch , the handle is the switch, it bolts to side of steering column . this switch controls the signals and the headlights and high /low beams. the other thing is the headlight switch connector, the connector some times goes bad and starts to melt or just comes out of the connector. you will need to remove the cover to steering column, the screws are located under the bottom cover in holes. remove cover and check connector and then test for power if you have power going into switch but not coming out then switch is bad.
the last thing is to make sure the bulbs are good , make sure the headlight bulbs are good , and also the driving light bulbs, test for power at the connectors to those lights to. You will need to do a little testing to find the problem.
if the fuses are good then you need to check for power and ground at the headlight plug that attaches to the headlight bulb if you have a good power and ground there and the connections are good then the bulbs are both no good.or if you can tell the bulbs are burnt out by looking at them then you don`t have to check powers and grounds.you also can directly feed power and ground to the bulb and check both the terminals for high beam and low beam as you cannot tell which is which by looking at the terminals
check for a bad ground or check plug and back track wires with test light till you get power and fix the wire. Make sure you check for a good ground first. If all fails then run a new wire from the other low beam light to the non working one.
Power flows from the battery to the main fuse. Then it flows to the control coil and contact side of the headlight relay. When you turn on the headlights, the headlight switch provides ground to the control coil in the headlight relay and that operates the contacts. The contacts allow power to flow to the right and left hand headlight fuses. Power flows to the headlights. The headlight switch is what provides ground to the high and low beams on the headlights.
To diagnose, remove the headlight relay. Using a voltmeter, check for battery voltage on terminals 3 & 4 in the socket with the key in the RUN position. Then turn on the low beams. Test for good ground on terminal 1 in the socket. If you're not getting ground, then you've got a problem with either a bad headlight combo switch or a bad ground. If you get good ground on terminal 1, reinstall the relay, turn on the low beams and test for power in the headlight sockets. If you get battery voltage, that confirms you've got good fuses and wiring up to that point. Next, check for good low beam ground on the red/green wire in the bulb socket. If you're not getting good ground, it's either a bad combo switch or bad ground from the combo switch. Then turn on the high beams and check for good ground on the red/yellow wire in the bulb sockets.
It wouldn't hurt to clean the ID ground on the left side of the instrument panel, but based on everything you've said so far, this sounds like a bad combo switch