Hello everyone,

Very strange problem for me here.. at night, I can't see the dash illumination at all on my 88 if I have my headlights on. If I turn my headlights off I can see them just fine because it lights right up. I *think* this means my bulbs are okay, doesn't it?

I know it's actually working because everything is displaying properly when I turn the lights off. I put it under some streetlights (dim, but a little light nonetheless) and I could see it a lot better but it's not nearly like I think it should be.

Anyone ever run into this? It was working fine yesterday. The only change I've made to the car is I replaced the heater motor.

Thanks much.


Update:
Put a bright light directly against the sensor and everything came on bright like it should. Tried turning the headlight **** and nothing changed. Still unable to read when completely dark, and can read it fine when the headlights are off.


[Modified by Tourney3p0, 4:29 AM 9/28/2002]

 

Did you install an aftermarket head-unit?

 

Actually, yes I did. This was almost a month ago though (Only had the car about a month and a half or two). It's been working flawlessly between then and yesterday. I'll take a look at it all tomorrow, but could you give me an idea of what you were thinking it may be?

For the record, I got rid of all the Bose stuff and used an adapter. Didn't cut any wires.

 

Rotate your headlight control counterclockwise and the dash will brighten.

 

Already tried turning the headlight control both clockwise and counterclockwise as far as they'd go. Clicked the control to turn on the internal lights as well, and they work. Still no illumination with headlights on.

 

Pull and check with an ohmeter your inst fuse and the tail fuse. If ok, then I would check the voltage on each side of the inst fuse as it is in series with the headlight dimmer control. The voltage on both sides of the fuse should vary when you rotate the headlight dimmer (rotate the headlight ****).

 

Tail fuse was fine, but inst fuse was blown. I'm quite sure that's my problem, but I won't know for sure until tomorrow since I don't have a 3 amp fuse laying around.

Question though.. I wonder why my Inst fuse would have blown in the first place? I did the radio work myself a month ago, and the illumination worked afterword. I made sure to unplug the negative terminal.

Actually, come to think of it.. I did one other small job. I removed the panel around the automatic shifter to get to some screws that the previous owner let fall through the cupholder. The 12V "cigarette lighter" that's in there had been pulled apart for some reason or another, so I hooked it back up. Maybe it had been pulled apart for a reason.. I'd understand it more if I could find the Inst explanation in my manual.

 

I confirmed that it was the Inst fuse. I suppose I would have eventually figured it out, but you guys were a huge help in getting me there.

I guess what threw me off was that the headlight control potentiometer (or rheostat? One of those variable resistors..) was on a different circuit than the illumination itself. Since it worked when headlights were off, I figured it wouldn't be a fuse. That's what I get for assuming.

I'm still interested in why the fuse blew in the first place though.

Anyway, thanks again.

 

Ugh, my suspicion was confirmed. Fuses don't just blow on their own. Replaced the fuse, all was well. Turn on the car and it's immediately blown again. Okay, so the lack of illumination when it's pitch black out is caused by a blown Inst fuse. Great.

So.. what would blow the inst fuse? I looked in my factory manual (not the factory service manual, just the standard one you get when you buy the car) and it shows a place for the Inst fuse in the diagram, but says nothing about what is on Inst's circuit.

Could someone help me out until my service manual arrives? Says nothing about Inst in my Haynes book either. I've done three things to the car that I think could possibly cause it.

1) Head Unit. I read on the forums that one particular wiring harness was incompatible in some way, and it was causing someone else to have this same problem. Can anyone confirm that?

2) Heater blower motor. Doubt this is it. Heat/Air is set to Off and lowest speed anyway.

3) 12V accessory (cigarette lighter). It was disconnected before. I reconnected it.

I did 2 and 3 at the same time, but 1 I did about a month ago. It worked fine until a couple of days ago so I have a hard time believing the head unit could cause it. The head unit itself works flawlessly. I removed the front door Bose speakers and replaced the rear speakers with Pioneer 6x9's. Again, it's all working flawlessly.

I don't have an actual lighter in the 12V accessory, so I can't test it with that. Just a retaining clip.

I'll be glad when my service manual arrives.


[Modified by Tourney3p0, 7:28 PM 9/30/2002]

 

Could be a bad short in the display itself feeding back to the fuse to blow it. See if your lights for the dash are blown.. (Inside the instr. panel).
Stuf liek this is usually a PITA to track down. Hope is this simple for you.

 

Forgot to follow up..

Problem was in fact with incompatibility in the head unit wiring harness. Strange how it didn't show up for a month.. but I disconnected everything but the bare necessities and it's working fine now. Haven't blown the Inst fuse since.

Just thought I'd follow up, if for nothing else future archive searchers.