Dash illumination won't work, radio ok, all lights ok, but when lights turned on NO dash illumination, dimmer ok, bulbs ok, show ground on red/green but can't find where it is, fuses ok

Oh boy, I just went through this with my '92 Lesabre, took a long time to trace it all down, and wound up splicing in a new wire just to my instrument cluster lights. A short kept blowing fuses somewhere in that circuit.
Down where your feet go, up under the dash at the fuse panel, there is a 15 amp fuse for park/tail lights. When you hit the light switch (for heads or park lights), power is sent to that fuse, and then to the exterior park lights. There is another wire from that fuse (green wire on mine) that also goes up under the dash, and splices to several bulbs-on the radio, on the HVAC controller, on the ashtray light, also one to the under hood lamp, and then one to the dimmer/brighter switch on the dash, the rheostat that controls brightness of interior lights. One of the green splices goes into this switch, and then another wire goes from this switch to the instrument cluster for the gauge and dash illumination. I couldn't find the short, so ran a new wire from the park light fuse to the gray wire to the instrument cluster for the cluster bulbs. I bypassed the dimmer, and left off the HVAC bulbs and ashtray light. Too much trouble to wire them all up, and think my short may have been in the dimmer rheostat.
If you have a voltmeter, pull out the dimmer switch and check for power on those wires, the green from the fuse. The park light must be switched on, or the fuse has no power. There be 8 or 9 wires on that dimmer rheostat-I never did figure out where all of them went. Asked all over a Buick forum, but nobody had an answer.

You have it right. Use a 12 volt test light to see if there is power between the gray and brown wires when the key is on. If there is power there, you may have got hold of a bad radio.


1990 Toyota Celica Car Stereo Radio Wiring Diagram
Radio Constant 12V+ Wire: Blue/Yellow, connects to yellow
Radio Switched 12V+ Wire: Gray, connects to red
Radio Ground Wire: Brown, connects to black
Radio Illumination Wire: Green, do not use
Radio Dimmer Wire: N/A
Radio Power Antenna Trigger Wire: Black/Red
Radio Amplifier Turn On Trigger Wire: N/A
Front Speakers Size: 4? Speakers
Front Speakers Location: Dash
Left Front Speaker Wire (+): Pink
Left Front Speaker Wire (-): Purple
Right Front Speaker Wire (+): Light Green
Right Front Speaker Wire (-): Blue
Rear Speakers Size: 5 1/4? Speakers
Rear Speakers Location: Side Panels
Left Rear Speaker Wire (+): Black
Left Rear Speaker Wire (-): Yellow
Right Rear Speaker Wire (+): Red
Right Rear Speaker Wire (-): White

This should help.


1987-88 Plymouth Voyager Stereo Wiring
Constant 12V+
Red
Switched 12V+
Red/White
Ground
Ground/Back Strap
Illumination
n/a
Dimmer
Orange/White
Antenna Trigger
Yellow
Antenna
Right Front
Front Speakers
5 1/4" Dash
Left Front (+)
Green
Left Front (-)
Green/Yellow
Right Front (+)
Purple
Right Front (-)
Purple/Yellow
Rear Speakers
6" x 9" Tail Gate
Left Rear (+)
Brown
Left Rear (-)
Brown/Yellow
Right Rear (+)
Blue/Red
Right Rear (-)
Blue/White

When you put the stereo in, what did you do with the red wire with a green stripe? The aftermarket radios don't always use these, so you have to wrap the ends, depending on whether or not you used a wiring harness. If that wire is shorted on the chassis, it will blow the dimmer fuse.

1995 Honda Accord Car Radio Wiring Diagram
Car Radio Battery Constant 12v+ Wire: Blue/White
Car Radio Accessory Switched 12v+ Wire: Yellow/Red
Car Radio Ground Wire: Black
Car Radio Illumination Wire: Red/Black
Car Stereo Dimmer Wire: Red/Green
Car Stereo Antenna Trigger Wire: Yellow/White
Car Stereo Amp Trigger Wire: Violet/Red
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: 5 1/4?
Car Audio Front Speakers Location: Doors
Left Front Speaker Positive Wire (+): Blue/Green
Left Front Speaker Negative Wire (-): Gray/Black
Right Front Speaker Positive Wire (+): Red/Green
Right Front Speaker Negative Wire (-): Brown/Black
Car Audio Rear Speakers Size: 6 1/2?
Car Audio Rear Speakers Location: Rear Deck
Left Rear Speaker Positive Wire (+): Blue/Yellow
Left Rear Speaker Negative Wire (-): Gray/White
Right Rear Speaker Positive Wire (+): Red/Yellow
Right Rear Speaker Negative Wire (-): Brown/White

The dash board has many light bulbs and the gear shift and the window switch all work on this circuirt. The radio if its stock turns up and down on this circuit too. The running lights are relaed to this circuit too as the runnings lights go out the dash does too. ( It's a DOT thang ) Lets you know that your running without tailights! But the dash can go out by it's self and aftermarket radios and their installers are the culprit. The dash light wire is in the stock radio harness and their used as ground wires and left to touch ground and blow the fuse. The fuse is called gaugesand it's a 5 amp or 7.5 amp. It's in the dash board fuse box behind the change holder that your left knee might hit if it were to hit the dash. If all the lights in the heater control and the gauges and the gearshift and the power window switch are all not working look for a blown fuse and it's cause. ( radio wireing ) or the running lights are out too and a bad marker light frunt or rear running lights. the park fuse may be blown and cause this and the dash lights won't work either. The dash dimmer switch can and does fail. It pops out by prying it out the frount theres 3 wires on it one is ground. one comes on with the lights and the other is the one going to all those light bulbs I just talked about. With the lights on one wire will be hot ( use a test light to check) A cheap one at the parts store or wally world only costs a few dollars at the most. If two wires are hot its on and it's godd one of these two will brighten and dim as you turn the switch. if only one wire is hot and the others stay cold the one that is hot jumpered to the one thats not black (ground) will make the lights work. Your right you could have bad bulbs but theres at least 15 of them and whats the liklyhood of blowing all of them at once ( doesn't happen unless theres a real bad problem involving crashes and jump starting. The cluster comes out by removeing the covers and then the speedometer cluster itself. If any of the lights work that the dimmer controls work and the gauges are't lit then this is the direction your going.

Check the dimmer switch to your dash light. If there turned down, your dash and radio illumination light will be dime or not working at all. Keep me posted, be glad to know if it is the dimmer switch turned down or you dimmer switch has gone bad. Good luck

Check that your tailights/parking lights are working (not the headlights) as this fuse and relay feeds all the instument lights too.... Fuse 15amp TAIL & Tailight Relay

If not then check:
The rheostat (also known as the dimmer switch) may be faulty
as it controls all the illumination of all the backlight bulbs and other dimable switches/indicators.

In general bulbs all together draw a fair amount of current so it is possible that the wiring or ground at the major supply junction feeders has failed but that is a less common problem.

So check the rheostat dimmer wiring area first as all illumination power goes through it.

There is further simple testing we can do with the three wires at the rheostat you can check the entire illumination system.
If you jumper the white/blk to the white/blk all the illumination lights should come on (that means the rheostat is bad).

Or use a voltmeter and measure the green rehostat wire to ground it should be 12volts (if not time to check the fuse, relay and wiring)

If not then finally declare the instrument panel faulty (like burned up circuit board trace).

Note of interest: the rheostat also controls (dims) other switches not associated with the instrument cluster such as the cigarette lighter bulb and hazard switch and radio player and A/C control switch. So if those are dimming but not the instrument panel backlights then yes the instrument cluster needs fixing or a very close wiring inspection.

Hello manchie...You should have a dash light dimmer switch..remove it from the dash. There should be a 3 wire plug on the back side with a Red/Green, Green/red and black wire. Jump between the Red/Green wire and the black wire and see if the lights come on. If they do, it probably has a bad illumination controller.
Good luck and i hope this will fixya up.

did u know that they make a harness for your car that plugs into your factory harness and then adapts to your aftermarket radio? for the lights, you have blown the interior light fuse, it may be the same fuse as the cigar lighter.Below is your radio wire colors and what they do.
1990 Toyota Corolla Car Stereo Radio Wiring Diagram.
Radio Constant 12V+ Wire: Blue/Yellow
Radio Switched 12V+ Wire: Gray
Radio Ground Wire: Brown
Radio Illumination Wire: Green
Radio Dimmer Wire: N/A
Radio Antenna Trigger Wire: N/A
Radio Amp Trigger Wire: N/A
Front Speakers Size: 4′
Front Speakers Location: Dash
Left Front Speaker Wire (+): Pink
Left Front Speaker Wire (-): Purple
Right Front Speaker Wire (+): Purple
Right Front Speaker Wire (-): Light Green
Rear Speakers Size: 4′
Rear Speakers Location: Rear Deck
Left Rear Speaker Wire (+): Black
Left Rear Speaker Wire (-): Yellow
Right Rear Speaker Wire (+): Red
Right Rear Speaker Wire (-): White
-->

Red - Power
Yellow - primary power must be joined to the red
blue - Remote
Black - ground or negative
To find your speaker wires check the color of the cord behind each speaker than match it with the same color in the dash.
or the easy way is to use a normal 1.5v penlight battery and try each speaker cord behind the dash and listen to which speaker give off a crackling noise so you can get the balance on the cd player right.
If u trying to find power in the car and don't have a tester than get a 12v light or bulb join the negative to the body and push the positive wire into each one of the holes in the factory plug in the dash one at a time until the light comes on. That is your positive the rest is easy. (DIY guru)