How To Test/Remove Headlight Switch?

[CVD]

My headlights stopped working, no high or low beams. Running lights, brake lights, turn signals, dash lights and overhead light (with dimmer) all work properly. This is a 1999 Winnebago on a Freightliner XC chassis.

I looked for a fuse, found none. I did find a relay hanging (literally) off the 7 wire harness that attaches to the headlight/dimmer switch. I’m guessing it’s for the headlights. I tested that relay, it’s good (I also swapped in a known good relay, no difference).

When testing the relay, I tested for current across the “switching circuit” by putting a test light across pin 86 and 30. With the headlight switch pushed in (off), no test light. With the headlight switch pulled out (on), I did get a test light. So, I think the switch is driving that relay and the switch is good.

I tested for current at the headlight housings; none at any of the four housings. Somewhere between the relay and the actual headlights, I’m loosing current on this circuit.

I looked at the Freightliner wiring diagram and see the path goes from the headlight switch to the high/low beam dimmer (no mention of the relay). I guess my next step is to trace down that high/low dimmer (it’s probably somewhere in the steering column). Before dive any deeper into this, a couple questions”

1) Any suggestions on something I’m overlooking?
2) Where is that high/low dimmer switch? Do they commonly go out?
3) I want to look closer at the headlight switch, just to confirm that’s not the problem. I’m not sure how to remove the box. I see a spring loaded button on the box (middle of picture below). I tried pushing in the button while pulling out the light switch, but it’s as if pushing it in actually holds the shaft in place. It doesn’t free the shaft to slide out (as I’ve read in other posts). Any suggestions on getting the switch box out?

[1BryNelson]

Your going to have to open the steering column plastic cover to identify the dimmer switch. Then you can get to it to be sure it's not an open circut. It should always pass voltage when headlight switch is ON.

[APRSRVer]

Circuit breaker for headlights is in headlight switch. If you have voltage for headlights out of the sw look for dimmer sw. Many are low on steering column operated by a rod down from lever on column. Or it may be a combo sw with wipers in column below steering wheel. I'd use a mechanics test light and probe the wire connector at the base of the steering column for a light that comes on with headlight sw and changes with operation of the dimmer sw. If that proves to be ok then the problem is between there and the headlights.

[1BryNelson]

Have you found the high/low dimmer switch? Thinks where I'd be looking next.

[CVD]

Thanks - got the switch out. I think it’s ok (see below). I’m back to looking for the fuse/relay/circuit breaker that controls the headlight circuit. Has anyone found this on a late 90’s Freightliner XC chassis (preferably from Winnebago)?

Here’s how I tested the switch - there is one full time powered pin, one ground (grounded to the switch body), and 6 other pins with wires going to them. With the switch removed, I tested continuity across the various pins.

With the switch shaft pushed in all the way (off), I got continuity across one set of pins – this had to be the dome light. With it pulled out half way, I got continuity across 3 pin sets (must be running lights, dash lights, and something else). With it pulled out all the way, I got continuity across the same pins as when halfway out, plus one more set (must be the headlights). All this makes me think the switch is good.

I must be overlooking something obvious. Back to the Freightliner wiring diagram - the light switch feed an “auxiliary light relay”, but it shows the tail light circuit going to this relay. The headlight circuit goes to the dimmer switch, then to the headlights. I don’t think the relay I found controls the headlight circuit, which means I haven’t found a fuse or circuit breaker for the headlight circuit.

Suggestions?

[RLS7201]

Cliff, pull the headlight switch out all the way (headlights on) then push the release button and pull the lever out.

Richard