Dimmer Switch Issue

[RangerReviver1990]

So I bought my '90 Ranger about 4-5 years ago as a little project vehicle. And I've been tinkering with the interior for the longest time and I've always been used to my dimmer switch being a little wonky. The headlight aspect of it worked just fine, but the dashboard never dimmed when I turned the knob to the right. Couple days ago, I went to a junkyard and snagged a dimmer switch of an '89 and installed it, thinking it was just the dimmer switch. I got home and installed it and now my truck has daytime running lights, which wasn't functional with the old switch. But something else that struck me as odd was the dashboard and the interior light could dim and the door chime would get quieter and eventually turn off, but only if the truck was off and I pulled the headlight switch back 1 click to the parking light position, and when I turned the key, only the daytime running lights would dim. Could this be a wiring issue from the switch to the instrument panel or something?

 

[RobbieD]

Sounds like it, but the "DRL" part throws me (unless something is trying to ground through the headlight filaments). Ground problems can create some pretty wild symptoms, so start there.

Instrument illumination grounds with G103, on the driver inner fender. See the schematic and the the G103 location drawing.

Beyond that, I'd look for rotten connectors and splices within the harnesses. And if any of the lighting has been changed from OEM stock, that needs to be checked, too.

 

[RangerReviver1990]

Sounds like it, but the "DRL" part throws me (unless something is trying to ground through the headlight filaments). Ground problems can create some pretty wild symptoms, so start there.

Instrument illumination grounds with G103, on the driver inner fender. See the schematic and the the G103 location drawing.

Beyond that, I'd look for rotten connectors and splices within the harnesses. And if any of the lighting has been changed from OEM stock, that needs to be checked, too.

View attachment 104004
View attachment 104005

Would this explain why everything works as it should until the turn the key? and the reason why my dashboard lights cant dim?

 

[RobbieD]

Yes, I can see that being the case for two scenarios. Key "on", first, more stuff is powered up, and trying to ground through a flaky ground point that otherwise works OK to a point; and second, a circuit with a bad ground can find a ground path through a related non-powered circuit, but once that second circuit is powered the ground path is taken away from the first circuit. The second scenario can seen a lot in lighting systems, one symptom being bulb filaments glowing un-expectantly from the current load. Hence your description of "now my truck has daytime running lights" leads me to suspect that you may have a grounding problem.

I'm assuming that your truck is not equipped with DRL (I think that Canadian trucks were, and Ford did offer them). And ground problems are pretty common, especially as a vehicle gets some age on it.

If were me, I start with looking at the truck's grounds and work from there.

Good luck!

 

[RonD]

New 1990 Headlight switch is $35
Not cheap but.................,neither is your time

You had a problem then swapped in a used switch and got a different problem
If it was the wiring and not a switch problem you would have the same problem, not a different problem

These older Main light switches pass high AMPs so tend to fail over time, so used is a roll of the dice, worth a try but...................if it was a wiring issue then same problem would occur, exactly the same problem, or it would have fixed the problem if the other switch was OK
So now you have 2 used switch and...............??

 

[SenorNoob]

I've found those switches tend to fail in weird ways like that too. Also had a couple with the shaft fall out.

Haven't a problem with a switch (My choice of the cheapest kit on e-bay is another story. Should really build my own.) since I started using the relay kit to power the headlights. Lights are noticeably brighter too.