2000 4runner dimmer switch burning up

[4runner9808]

hello out there ! i have a 2000 4runner and my dash lights stopped working ...i have purchased a new dimmer switch from toyota dealer and plugged it in and turned on the lights and it started smoking ...i also got a switch from a junkyard and it did the same thing...does anyone have any idea what may be causing this to happen?...thanks

 

[BigFishAllDay]

Did you recently add an electrical circuit that taps the dimmer wiring?

For example: guages, interior lighting, etc?

The dimmer switch is a Rheostat... it controls how much current is allowed to go to ground by altering the resistance of the circuit.

Picture it like this (power flows in the direction of the > ):

12 V source ----------- > (pos) + wire --------------- + > Device (all of your dash lighting / ash tray light /glove box light ) > - wire (neg, ground) > ----------------- > XXX (rheostat) >------------> ground.

By controlling how much current is allowed to go to ground, the rheostat controls how much current flows through the circuit... less current = dimmer lights, more current = brighter lights.

If you tap that circuit incorrectly, you can smoke the dimmer in an instant.

For instance, when I did my first guage install, I tapped the positive wire of the guage lighting into the dimmer circuit between the dimmer and ground. When I completed the circuit putting the ground wire to a body ground, it pulled too much current THROUGH the dimmer and it literally went up in smoke.

I'd say someone tried to wire something up and did it incorrectly. Otherwise you've got a short between the dimmer and ground.

Don't keep plugging in new dimmers, you'll just keep smoking them until you find the wiring issue.

 

[Brilliant]

Did you recently add an electrical circuit that taps the dimmer wiring?

For example: guages, interior lighting, etc?

The dimmer switch is a Rheostat... it controls how much current is allowed to go to ground by altering the resistance of the circuit.

Picture it like this (power flows in the direction of the > ):

12 V source ----------- > (pos) + wire --------------- + > Device (all of your dash lighting / ash tray light /glove box light ) > - wire (neg, ground) > ----------------- > XXX (rheostat) >------------> ground.

By controlling how much current is allowed to go to ground, the rheostat controls how much current flows through the circuit... less current = dimmer lights, more current = brighter lights.

If you tap that circuit incorrectly, you can smoke the dimmer in an instant.

For instance, when I did my first guage install, I tapped the positive wire of the guage lighting into the dimmer circuit between the dimmer and ground. When I completed the circuit putting the ground wire to a body ground, it pulled too much current THROUGH the dimmer and it literally went up in smoke.

I'd say someone tried to wire something up and did it incorrectly. Otherwise you've got a short between the dimmer and ground.

Don't keep plugging in new dimmers, you'll just keep smoking them until you find the wiring issue.

I'm about to do this so this is timely. Thanks for the explanation.

 

[Ron Helmuth]

well explained by BFishAD as always.

 

[BigFishAllDay]

I'm about to do this so this is timely. Thanks for the explanation.

No prob. If you want to put something new into the circuit, just find a dash light (I like to use the ashtray light) and tap the positive side of the new device into the positive wire on the dash light, and the negative side of the new device into the negative wire on the dash light (parallel wiring).

All of the dash lighting is a series circuit....

12V source > light > light > light > light > dimmer > ground

Alternately, you could just cut the positive wire feeding a light and wire the new device in series. That would reduce the current though the circuit a little bit, but if you're just adding some guages I don't think the lighting pulls enough current that it matters which way you go.

well explained by BFishAD as always.

Thank you sir!

 

[4runner9808]

dimmer switch burning up!!

is there a way to by - pass the dimmer switch all together and still get lights to the dash and a/c heat controls? i had the speedo cluster off today to see if there was something loose or something but had no luck..im not the best when it comes to electrical wiring ...i understand that there is 2 wire with current and one i guess is the ground ...three prong connector for the dimmer .could a aftermarket radio install be my problem of a short between the ground and the switch..?my lights worked fine after the radio was put in but sometime later my lights stopped workin..thanks to all who replied to my question i will try anything to get this working .. cause i cant keep spending 150bucks for dimmer switches and toasting them ...makes me sad!:cry2:

 

[4runner9808]

I'm about to do this so this is timely. Thanks for the explanation.

no new wiring all stock it just stopped working one day so i figured it was the switch

 

[4runner9808]

do u know of a way to bypass that switch all together ? is it possible

 

[BigFishAllDay]

I think you need professional, local help.

I'm not sure why you pulled the speedo cluster. If that wasn't touched, then there's no reason that it would be the source of your problem.

You stated that the only change has been the installation of an aftermarket head unit (radio). If I were you, that's where I'd start looking for the problem. And as I stated earlier, check for shorts between the dimmer and ground.

Who installed the radio? If it was done by a professional, you ought to take it back, describe the problem, and see if they can fix it.

 

[4runner9808]

yeah it was me that did the radio but the lights still worked after that was done then about a month later it started...how would i check if there is a short between dimmer and ground? where the switch plugs in at i have 3 wires im guessing the green in ground but i can only see where it has the connector plug and the rest is way back in the dash ... do the wire go to the fuse block? you r right i probably do need professional help in more ways than with this!thanks for all the help!

 

[Big John]

Since most head units dim with the rest of the lights these days, I suspect something went wrong with your install. Try disconnecting the new stereo completely, then see if you smoke another junk yard dimmer. I'd get this under control before we all get invited to roast marshmallows at your place.

 

[BigFishAllDay]

Below is a link to a Toyota Factory Wiring Manual for a 2002 4Runner. Take a look at the wiring schematic for the interior illumination.

First, click here >>> http://www.ncttora.com/fsm/1996/SIL/fsm/wiring.html

Next, open the link labeled >>> E.W.D. 2001-2005::2002 4RUNNER: Illumination

Now you're looking at the wiring diagram for the interior lighting. Scroll down to page 2, and you'll see the dimmer, labled as "R6 Rheostat", on the right hand side of page 2. Notice that all fo the wires eventually end up going through the dimmer, then to ground.

According to the diagram, the Dimmer shouldh have 3 wires attached to it, the White wire w/Black stripe being the ground wire. If you have a short, it would be on the White wire w/Black stripe.

However, as Big John said, since the radio install was the only thing that changed, and you did it yourself, that's probably where the issue is.

Notice on the wiring diagram, that (as Big John stated), the factory radio is tied in to the dash lighting circuit so that it dims along with the rest of the factory dash lighting.

Pull the radio that you installed, and check your wiring. See if you tapped into any of the factory wiring. Specifically, you'll be checking to see if you tapped into a GREEN wire or a WHITE W/GREEN STRIPE wire. Those are the wires that would have connected the factory radio to the dimmer circuit.

If you have tapped into those wires, that's where your problem should lie.

BTW, take some pictures once you get in there, because it will be hard to help you beyond this without more information/pictures from you.

Also, post some details on your 4Runner... mainly the model year.

 

[4runner9808]

ok cool thanks for the links i will try that ...i amnew to this forum and still learning the ropes thanks again to all for the help!

 

[Chichi]

I had a similar issue with my 99 4runner, my dashboard illumination lights would not come on when I would turn on my parking and headlights. My center console, AC, ashtray glovebox lights work fine.
I ended up fixing issue by replacing the rheostat and the illumination light bulbs inside the dashboard.

 

[T4R_Finally]

FWIW, when i recently posted a thread here about my upcoming new stereo install, a forum member warned me not to hookup the dimmer lead unless it was specific to the 4runner because it may burn my rheostat out due to something weird about the way toyota requires it to be wired. I did not connect that lead and have not even noticed a need for it. And all has been fine since.