soulbounder

Just so we are on the same page, I'm talking about this thing:

Firebird remote dimmer switch

I had an idea of where it was looking at old forum posts, but it was still quite difficult to get to, at least for me. I'm about 6'3", 240 lbs. I started by removing the three 7 mm screws on the front of the plastic trim piece under the dash and the 10mm nut/bolt/screw thing holding it to the firewall. Afterwards, I removed the 7mm screws on the back side of the convenience panel so it swing down further. After that, I tried to stick my head in the foot well and look up so I could see the part, but it still wasn't really possible. I could see it with a mirror at least so I was on the right track. I pulled the driver's seat and ended up laying down on my back. After pushing some wires out of the way, I couldn't see the part super clearly, but I could see enough to see the two 7 mm screws holding the switch in place. I had to use a 1/4" socket wrench and socket and it was still a pain. I only have down to a 8 mm ratcheting wrench so that is something I need to address. Those 7 mm screws attach to the metal bracket that holds the part (you can see the two empty holes.) To confirm that this is where my problem is, I bypassed the switch by taking the electrical connector and using a paper clip to connect the dark brown wire to the dark green wire (the one right next to it). I then turned on the headlights with the switch and all of my dash and console shifter lights came on at full brightness.

I now need to decide if I want to bypass the switch, replace it with a used $10-15 piece, a new $30-$45 aftermarket replacement, or try and find just a NPN transistor that I can use in its place. It looks like the OEM is a Motorola unit but I'm sure anything of comparable spec would work. if anyone has any suggestions on an equivalent replacement I'm all ears. Also, if anyone wants to see more pictures or video f something specific, just let me know. I can take some while putting it back together.

sofakingdom

iTrader: (1)

IIRC a 2N3055 works. You used to could get that at Radio Shack. Micro Center or Fry's probably would have it these days. If not you could order it from Digikey or Mouser.

soulbounder

I'll go to my local electronics place (Ace Electronics) and see if I can find one tomorrow assuming they are open.

sofakingdom

iTrader: (1)

Very possible that they might: it's an extremely popular and common part.

soulbounder

Well, just an update. Swapping the transistor did not fix the problem. When I bypass the transistor, I get full brightness. Could it be possible that the dimmer wheel is what is actually bad? My dimmer wheel does turn on the dome light when I put it all the way up. Is that a separate switch inside of the dimmer wheel assembly? That is the only way I could imagine it works given its behavior.

scooter

iTrader: (11)

The dimmer wheel is carbon resistor printed on a PCB, essentially, The carbon could be worn away, the contact could be pulled away or worn down. The detent for the dome light is a bump that pushes a different contact down. I am working on putting a PWM dimmer into that whole assembly to regulate some LED brightness. I put up a post about it. I haven't installed it yet though

soulbounder

That's what I figured. I guess it's time to figure out how to pull that dimmer wheel out so I can investigate. Hopefully I can get to it without removing the whole dash.

scooter

iTrader: (11)

You have to pull the cluster trim off to get to the switch and dimmer wheel, then it's 3 screws and 2 connectors

soulbounder

I got it out. Is there a way to test the switch? Does anyone know what the good resistance values should be?

The bottom two pins, with the switch all the way dim I see 98 Ohms. As I turn the wheel up to the bright side it increases and stops at 268 Ohms.
The center 2 pins go from open to closed as the once the wheel gets into the "turn the interior lights on" position.

Assuming I do need to replace it, what would be the best place to get a replacement?

scooter

iTrader: (11)

It's easy enough to take apart and look at it since you have it out. It's not a complicated assembly, only a few moving parts, not many parts in total. The wiper contact may just be carboned or dirty

soulbounder

I have it out, but the problem is that is looks like it works to me.
Without an understand of what is considered good values for the output and which pins are for what, all I can say is moving the wheel changes the electrical properties of some of the pins.
If the resistance changes from 98 to 268 Ohms on the bottom two pins when moving the wheel, is that within spec to make the circuit work?

scooter

iTrader: (11)

I don't know the spec, but chances are the carbon is worn in one spot. It's hard to get a good reading of how well an analog device, variable resistor, works with a digital multimeter. You really need a multimeter with a needle to see if the needle is consistent across the sweep.
In my car the carbon is worn in a spot so the dimmer wheel doesn't react properly in a certain range and the lights will get dimmer as I sweep through the range then get bright, even though it should be a linear increase in brightness through the sweep.

If you just open it up it might tell you what you need to know without knowing measurements. This is one of those things that is an extremely simple circuit, it may be a visible defect and be causing your issue. It's really easy to open if you already have it out. Just taking it out of the dash could have cleaned up the contacts in the connector, or on the wheel as you removed it. IIRC there is grease in there, the grease may just be old and dry and cause your issue.
There are two clips to take the resistor board off the housing and a spring to keep pressure on the wheel. Open it and take a look inside. You might find that you can just clean it gently with a some contact cleaner, wipe the contacts on the wheel to get the old grease off, put it back together with some new grease and find that it works properly again. You really have nothing to lose, but some time, if it isn't working now.
I would even use a little grease inside the female contacts in the connector when you put it back in to test it.

soulbounder

I don't see anything out of the ordinary. Do you know what kind of grease is used between the wheel and the copper tracings? It looks greenish, but I don't know what it is.