Headlight Dimmer Switch Issues

[homelessduck]

My cluster illumination was not working but everything else controlled by the switch worked fine. I finally got around to replacing the switch today. The cluster illumination will not turn off now. Ignition off , key out , cluster stays illuminated , and the dimmer portion of the switch gets hot. I can dim it all the way down , but the lights never turn off. The harness and plug is not melted at all. I have tried several different switches with the same results. It should be keyed on power , not constant to the cluster illumination right?

 

[Austin86250]

the dimmer switch is in the floor for high and low beams,
The light switch is for turning headlights and all other lights on aswell as dimming
it’s operated pulling outward and turning side to side when it is turned all the way ccw it will lock and keep many things on regardless of key, switch pull position

Also if it’s getting hot that means the switch is no bueno may be bad out if box

The light switch always has power going to it

 

[franklin2]

The cluster illumination is not fed by key on power. It's fed by it's own separate fuse in the fuse box that is hot all the time, and it feeds the exterior marker lamps also. This fuse feeds the main light switch. It does not feed the headlights though.

After it goes through the main light switch it splits off inside, one leg goes to the exterior marker light part of the switch, the other leg goes to the cluster dimmer part of the switch.

After it goes through the dimming part, it leaves the light switch and actually goes back to the fuse box to its own dedicated cluster illumination fuse. Then it finally leaves the fuse box on a blue/red that feeds all the cluster lights.

1st thing to do is pull the cluster fuse, they should go out.

 

[homelessduck]

the dimmer switch is in the floor for high and low beams,
The light switch is for turning headlights and all other lights on aswell as dimming
it’s operated pulling outward and turning side to side when it is turned all the way ccw it will lock and keep many things on regardless of key, switch pull position

Also if it’s getting hot that means the switch is no bueno may be bad out if box

The light switch always has power going to it

This is a 92 , different setup. The headlight dimmer isn't on the floor. However , I am talking about the cluster illumination dimmer , which is part of the headlight switch. I have tried several switches , even different brands , and they all get hot and the illumination stays on.

 

[homelessduck]

The cluster illumination is not fed by key on power. It's fed by it's own separate fuse in the fuse box that is hot all the time, and it feeds the exterior marker lamps also. This fuse feeds the main light switch. It does not feed the headlights though.

After it goes through the main light switch it splits off inside, one leg goes to the exterior marker light part of the switch, the other leg goes to the cluster dimmer part of the switch.

After it goes through the dimming part, it leaves the light switch and actually goes back to the fuse box to its own dedicated cluster illumination fuse. Then it finally leaves the fuse box on a blue/red that feeds all the cluster lights.

1st thing to do is pull the cluster fuse, they should go out.

So if it isn't key on , and is actually constant , what actually turns the cluster illumination off? I did pull the cluster fuse so the batteries don't drain while I figure it out. I was thinking it may be the ignition switch . But if it isn't key on powered , I'm not sure what it could be at this point.

 

[hacked89]

So if it isn't key on , and is actually constant , what actually turns the cluster illumination off? I did pull the cluster fuse so the batteries don't drain while I figure it out. I was thinking it may be the ignition switch . But if it isn't key on powered , I'm not sure what it could be at this point.

It’s the tumbling contact in the headlight switch.

 

[homelessduck]

It’s the tumbling contact in the headlight switch.

So when the dimmer is rotated it should dim down then turn off? It will dim down but it stays slightly illuminated.

 

[franklin2]

The headlight switch has several sections to it. One section is the headlight section and it has it's own separate power supply for the headlights, powered all the time.

Another section of the headlight switch is the marker lamps. This section is fed from a fuse in the fuse box. If you pull this fuse, the marker lights AND the cluster lighting will go out.

Inside the switch, the marker lamp power goes through it's part of the headlight switch section, then it y's out and feeds the marker lights directly, and the other leg goes to the dimmer in the headlight switch for the cluster lights.

Go out to any vehicle in your fleet, most of them will let you turn the marker lights and the cluster lights will come on without the key in the ignition.

 

[hacked89]

do you have the circuit to post for 92 Franklin? I have up to 91. Homeless - I was saying when atleast up to 91 there is a relationship between pulling out the headlight switch “marker vs on vs on” and the always on feed from the fuse box. It’s all unkeyed up to 91 and I’m sure it’s unkeyed in 92 like Franklin is saying. I’m pretty sure the contacts work similar because I use OBS headlight stalks in my switches since bricknose stalks aren’t available reproduction. Usual failure scenario is when it’s in marker or on position I’ll see no illumination and need to wiggle the knob. You have the reverse happening so I think you are “shorting” power.

 

[franklin2]

For troubleshooting, you need to find out where this stray power is coming from. First thing I would do is unplug the headlight switch. If they are still glowing, you know the problem is after the switch.

If they go out, the first thing I would do is carefully inspect the tan/white wire feeding the switch. This wire is famous for overheating.

 

[franklin2]

Another common problem area for this circuit is the radio. The cluster blue/red wire feeds the radio and dims the display when the lights are turn on. People miss-wiring aftermarket radios can easily cause problems.

 

[homelessduck]

For troubleshooting, you need to find out where this stray power is coming from. First thing I would do is unplug the headlight switch. If they are still glowing, you know the problem is after the switch.

If they go out, the first thing I would do is carefully inspect the tan/white wire feeding the switch. This wire is famous for overheating.

With the switch unplugged the lights turn off. And with the fuse pulled the lights turn off. I've inspected the wires and they all look good. I guess where I am confused is what actually turns the power off to the illumination. If there is constant power to the dimmer , and the only thing controlling the power from there to the illumination is the dimmer rheostat (?) ... there is no off setting . There is only clicked on , then when it is rotated it makes contact with the spring all of the way to low dim, but doesn't click "off". So it is technically always drawing some power.

 

[hacked89]

The circuit opening when the stalk is pushed all the way in. Or are you looking for more specific?

 

[Rdnck84_03]

There is only clicked on , then when it is rotated it makes contact with the spring all of the way to low dim, but doesn't click "off". So it is technically always drawing some power.

The rheostat should be dead with the headlight switch pushed all the way in. The on position on the dimmer only controls the dome and cargo light.

Is it possible something in the dash is touching the rheostat and shorting it to the dome light power?

James

 

[homelessduck]

The circuit opening when the stalk is pushed all the way in. Or are you looking for more specific?

Ok , gotcha. For some reason I thought you guys were saying the cluster illumination would still have power with it pushed all the way in. So I was trying to figure out how the rheostat portion was supposed to turn it off. So the cluster illumination should only turn on with the switch pulled out. Ok , so it is likely shorting power to that terminal , which could be through the switch plug. It could also be a faulty switch , but I've tried several so probably not the switch. It does have an aftermarket stereo in it , but it turns off with the key off , and the dimmer doesn't affect its brightness at all. I guess it would be worth a shot to pull it out and have a look just in case.