99 XLT 4x4 with fog lamps. I'm bewildered...New dual filament bulbs, new light switch, new multifunction switch... no hi beams, even on flash to pass. When I throw the switch forward, fog lamps stay on but lights go out...???

 

If the fuses are good, you need to go out there with a voltmeter and trace the circuit, beginning at the fuse, which should have voltage. I don't know what sequence you replaced the parts in (bulbs first?), but there was once in my life that I fixed this problem on a pickup that for no apparent reason, managed to burn out both low beams at the same time. Who would have ever thought...........

 

Check fuse 33 (15 amp) bottom left fuse. If its good, check your multifunction switch connector.

 

When you check the fuse use an ohm meter not your eye. If the fuse is ok the next steps.




Measure the resistance between LH headlamp C147-2, circuit 12 (LG/BK), and fuse junction panel fuse 33, pin 2.

l Is the resistance less than 5 ohms?

è Yes

RECONNECT the LH headlamp. Go to «C3».


Place the headlamp switch in the ON position.

2 Verify the multi-function switch is in the high beam position.


Measure the voltage between fuse junction panel fuse 33, pin 1, and ground.

l Is the voltage greater than 10 volts?

è Yes

REPLACE the headlamp bulbs. TEST the system for normal operation.


Measure the resistance between multi-function switch C254-12, circuit 632 (GY/O), and fuse junction panel fuse 33, pin 1.

l Is the resistance less than 5 ohms?

è Yes

REPLACE the multi-function switch. TEST the system for normal operation.

Measure the resistance between LH headlamp C147-2, circuit 12 (LG/BK), and ground.

l Is the resistance greater than 10,000 ohms?

è Yes

RECONNECT the LH headlamp bulb. REPLACE fuse junction panel fuse 33 (15A). Go to «C6».

 

I had read in an earlier post to check fuses 4 and 8 for the headlites. They were fine. Never checked 33. Guess what... whalla, hi beams. Thank you for your help!

 

Each low has a fuse then a common for high.

So there is 3