Brenjen

So; I put in my ARB switches (3) & connected the appropriate wire to the dimmer. The dimmer has one 12V constant, one ground wire & one 0 - 12V variable (out from the rheostat). I connected my ARB switches to the 0 - 12V variable wire controlled by the rheostat so I could have my switches dim with my dash lights.

Here's the pickle - when I turn the knob to dim my dash lights the switches get brighter......when I turn it back to brighten the dash lights; the switches dim!

I took it apart & could not figure out what the deal was so I just spliced it into the constant 12V going into the dimmer & they light up (no dim function though). My dad swears the wiring on the switches must be wrong but they are all wired correctly according to the diagram.


Does anyone have a clue why this is? It's nagging at me.


EDIT: P.S. the dash lights have worked 100% correctly the entire time; they've never operated backwards to the dimmer

__________________
'95 4Runner 3.0 Automatic bone stock; it's becoming a project slowly but surely, one part at a time

"If ye love wealth better than liberty, the tranquility of servitude than the animated contest of freedom, go from us in peace. We ask not your counsels or arms. Crouch down and lick the hands which feed you. May your chains sit lightly upon you, and may posterity forget that you were our countrymen!”

4Crawler

The reason is that the dimming dash lights share a common ground path through the dimmer. Lighted switches typically have a single power lead for the light and it is grounded to the switch ground. So if that is hooked to the dimmer, the switch light is essentially wired in parallel to the dimmer and thus will work opposite to the rest of the dimming lights. When the dimmer is on high brightness (i.e the lowest voltage drop across the dimmer), the switch light will be dim. When the dimmer is on lowest brightness (i.e. the highest voltage drop across the dimmer) the switch light will be the brightest.

Two options are to have a switch light with both light leads available so that it can be wired to the dash light power and to the dimmer/ground path. Or just wire the single switch light lead to constant 12 volts and have a single brightness.

__________________
1985 Toyota 4Runner SR-5, 22REC engine, dual t-cases, 4.88 gears, dual ARBs, 33x10.50 BFGs.
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Brenjen

Wiring to the 12V "IN" (lead) is what I did & I'm calling it good, but it was bugging the hell outta' me as to why....with no voltage going to the switch wire it would brighten & then dim when it cranks up to >12V

The truth is, if it's really - REALLY simple I can muddle through w/vehicle electrical systems but if it gets even as complicated as what you just described I'm at a complete loss. To me a ground is a ground is a ground


Thanks 4crawler; I figured you'd have the answer.

__________________
'95 4Runner 3.0 Automatic bone stock; it's becoming a project slowly but surely, one part at a time

"If ye love wealth better than liberty, the tranquility of servitude than the animated contest of freedom, go from us in peace. We ask not your counsels or arms. Crouch down and lick the hands which feed you. May your chains sit lightly upon you, and may posterity forget that you were our countrymen!”

4Crawler

It would be so nice if all the switch makers would just supply both leads for the light bulb (or LED) to connect to. Then if I wanted it tied to ground, I could put in a jumper and if I wanted it floating (like Toyota does), I could do it that way.

Sometimes you can put the switch in wired opposite and make it work. That is swap the power and ground connections and use the switch to switch ground instead of power. Then tie the light across the dimming bulb circuit. At least that works for things you want to work when the lights are on and also only works with incandescent bulbs (not LEDs).

__________________
1985 Toyota 4Runner SR-5, 22REC engine, dual t-cases, 4.88 gears, dual ARBs, 33x10.50 BFGs.
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Project: 4Crawler
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Brenjen

So from what I gather, the rheostat is varying the ground instead of the power?

Man....it's hard to be dumb like me with electronics. I understood exactly how to make it dim with the dash lights from your first post but still don't understand why/how it doesn't work tied into the variable voltage & I know you can't write the "vehicle electronics for dummies" handbook in a thread on Yota-Tech lol

I don't feel too bad; my dad has got 50 years of electronics background & a college degree in it & he didn't know why it wouldn't work either.....he's 72 today though & his memory is starting to go South on him so that's probably why he doesn't get it either.....what's my excuse?

__________________
'95 4Runner 3.0 Automatic bone stock; it's becoming a project slowly but surely, one part at a time

"If ye love wealth better than liberty, the tranquility of servitude than the animated contest of freedom, go from us in peace. We ask not your counsels or arms. Crouch down and lick the hands which feed you. May your chains sit lightly upon you, and may posterity forget that you were our countrymen!”

4Crawler

Look at the wiring diagram in a Factory Service Manual. Going by the '85 FSM I use:. For the dimming lights you basically have a relay (Tail Light Relay) that supplies 12 volts to all the dimming lights. Then all the lights are tied on one side to that power. The other side of all the dimming lights are tied together and connect to the dimmer/rheostat (i.e. a variable resistor). Then the rheostat connects to ground. So at full brightness, dimmer=minimum resistance, you see 12 volts across the lights, 0 volts across the rheostat. At minimum brightness, you might see 6 volts drop across the rheostat, so the light bulbs only see 6 volts across them, but since they do not tie directly to ground, you'll see 12 volts on one side of the light bulb and 6 volts on the other side (i.e. the side tied to the rheostat). So you'll see a variable voltage across the lights, but that voltage is floating and not referenced to ground. When you measure the voltage relative to ground you are measuring the voltage across the rheostat since it is the part connected to ground. When you put a light bulb between that point where the lights connect to the rheostat and ground, that light bulb is in parallel to the rheostat, not in series with it. Hook up your volt meter again and see what your "variable voltage" is doing, at full brightness, it is likely near 0 volts and at full dim, it is likely 6 volts or higher. So it is basically going opposite of what you want to make your switch's light bulb do the same dimming as the dash lights.

If you have a look at this page:
http://www.electronics-lab.com/artic...ry/circuit.htm

The stock setup is something like this:


where "Load2" is the combination of dimming lights and "Load1" is the dimmer/rheostat.

When you add your lighted switch between the center point and ground, you create a circuit like below:


where "Load3" are the dash lights, "Load1" is the rheostat and "Load2" is your added light bulb.

__________________
1985 Toyota 4Runner SR-5, 22REC engine, dual t-cases, 4.88 gears, dual ARBs, 33x10.50 BFGs.
r.c.brown@ieee.org
TruckEditor@tlca.org
Project: 4Crawler
4Crawler OffRoad
Gettin'Off 4WD Club