No instrumentation backlighting?? No power mirrors?

[TecNickal]

90 Town Car...hope this is OK to post here since it's a 5.0...

So my gauge cluster works. The clock turns on/off. When I turn on headlights, the clock dims.

But...I have no backlighting for anything - light switch, auto-dim range, HVAC, stereo, fuel door, etc. No backlighting and no owners manual to check either.

Is there a specific fuse to look at?

My power mirrors do not work. And no backlighting on anything. The digi dash works fine, but gear indicator has no backlighting. The footwell lights, the overhead lights, the moonroof, the power windows and power locks all work.

[DerekTheGreat]

I highly recommend the service manual for every car that you buy. Not that Chilton/Hayes crap but the actual official manual. Those things have been nothing short of awesome for helping me troubleshoot electrical crap for our cars.

Anyhow, in your case I'd check the owners manual for a possible fuse that has blown. If it was working before that's what I'd suspect. That or the main main feed line for those things as I doubt they all share the same ground. I was having an issue with the speedometer not working on our GMC. Everything else on the cluster worked but the speedometer. That cluster has two feeds and only one of them worked. I ended up tracing the problem back to the fuse block, one of the terminals had corroded so while the fuse was good, no current was passing through the corroded ends. Fixed that up and bam, speedometer works once again.

[Kodachrome Wolf]

Sounds almost like troubles I was having at Carlisle, but missing some of the affected areas. I'm not sure if there is a dedicated fused circuit for dash illumination or if its tied into another circuit. I'd start by checking for any loose wires, and if you haven't found the problem, I do have a open circuit tester if you'd like to try it this weekend.

[gadget73]

Should be a low amp fuse for that. 5 amp or so. Could also be the dimmer control on the headlamp switch. Also, make sure its not just turned all the way down.

[GM_Guy]

Have you looked to see if your parking lamps still work?

Alex.

[TecNickal]

Parking lights work with or wiThout auto lamp. The knob on headlight switch does not adjust dimming. Turning lights on dims the clock some. That's it. No backlighting for the gear indicator or anything else and no power mirrors.

[DerekTheGreat]

Kinda says it's not the switch as the clock is responding. Does the clock respond to the dimmer? Have you bought that service manual??

http://www.ebay.com/itm/1990-LINCOLN-TOWN-CAR-MERCURY-MARQUIS-FORD-CROWN-VICTORIA-FACTORY-SERVICE-MANUAL-/361389515768?hash=item54247e63f8&vxp=mtr

Could be a fuse but most certainly has to do with the main power feed for that circuit. Mr. manual is your friend here, you will love manual long time.

[TecNickal]

I ordered EVTM and wiring diagram duo for $20 shipped on eBay last night, so hopefully they arrive before long.

Clock does not respond to dimmer - all it does is just dims to default nighttime mode?

I picked up an owner's manual, but the way it's described in there, I don't think the issue resides with a fuse, as other functions tied to fuses that handle the Dimmer, are working fine.

No power mirrors, and no background lighting w/controlled dimming is all I have at the moment.

[DerekTheGreat]

Yeah I got nothing. When that manual plops in you'll have to scour it. Those things are awesome for troubleshooting.

[sly]

I'm wagering fuse weirdness or loose ground/wire somewhere.

[TecNickal]

The Speed Control light does not illuminate on the dashboard either. There's something going on clearly!

The overhead lights is because someone removed the contact points for the ceiling lights. I have a donor switch bezel/panel to install and see how that fixes it.

I have the wiring diagrams and books, and since this car has piece it together approach with doors from other vehicles, it could be a wiring issues inside the door or into the body.

BTW - Ford was stupid for not having disconnects for the door wiring. Seriously - the harness goes from the body, through the grommet/accordion into the door. No disconnect anywhere.

[DerekTheGreat]

Yah, looks like you need to start ripping stuff apart and testing for voltage and looking for shorts. Fun stuff.

[gadget73]

Boxes were built the same way. Its a real bitch changing those doors. Have to fish all that nonsense out, then get it all back in and routed properly so the window doesn't chew it up.

[TecNickal]

what a bunch of non-sense. I'm tempted to make my own wiring disconnect.

And I pulled every single fuse and visibly looked at it last night. The only bad one I found was air pump 30 amp fuse.

Also possible I have a melty connector for the headlight switch or a bad headlight switch.

We'll see....

[DerekTheGreat]

A good fuse doesn't mean power is even getting to it!! That was the issue with the speedometer in the GMC all along. I initially checked the fuses but all were good so I put that behind me. Later on the troubleshooter manual pointed me back there and upon closer examination I found the "hot" end of the fuse clip was corroded, and it broke away when I probed it for power but until it broke away, meter read 0.00 volts. Broke it and I had 12.xx. Not saying you'll have the exact issue but if you do have power in the right place then you get the fun exciting time of digging deeper.