Hi guys, I am in the process of trying to get an old 87 DL back on the road, I have it mostly running good but was out on a test drive yesterday and noticed that the clock and dash illumination had stopped working. Checked the fuses and the dimmer everything was ok, finished the drive with the lights not working (hvac and all other lights work). Started it today and everything worked great. Drove it around a bit (10-15 miles) and it all was good to go. Started it this evening and the gauge illumination wouldn't work again and clock is being weird. Everything else works though, Radio lights, hvac lights, dimmer lights, hi beam indicators, parking break light etc. just no illumination behind gauges. Also I noticed that the break fluid light EGR and check engine light were sort of glowing ever so slightly with the idle, this seems to go away when you rev it up a bit but comes back when idle comes back down. I tried smacking the side of the dash and that brought everything back for a few minutes but then the illumination lights quit working again. I haven't checked anything with a multimeter yet, that will be for tomorrow. For now I am just trying to see what some others think the issues could be, I will be at the junkyard tomorrow and want to add as many parts to my list as I can. I am thinking I could have 2 issues, maybe the alternator and the illumination control module? its also worth mentioning here that the electrical in this car was pretty messed up due to some mice living in it for a few years as it sat. I have already soldered a few connections back together in order to get the gauges to work correctly, and everything was working right for a while which makes me think it could be a failing component not just a chewed wire... Any help would be awesome. Thanks guys.

Kept thinking alternator while reading through the post, then I hit the bit about mice. That throws a little wrench into the mix haha. Throw a new alternator in it and see if that solves anything, and then I guess start multi-metering away.

Damn mice.

Yea mice are right up there with salt water as far as wreaking havoc on wires goes.... Guess I'll start pluging away.

The alt or a bad ground. A bad ground can do the same thing. Start checking them out.

If the alternator isn't turning fast enough to keep the charge on the battery up the warning lights will do what you describe. Cleaning the battery to chassis ground connection and engine grounding may help some. The problem with the dash lights could be due to a dirty connector pin. Seperating and reconnecting the connectors might solve that issue. Check to see if the red wire on the light switch has power getting to it when the trouble happens. The switch may have a problem.

next time the illuminatiopn goes out, mess with the dimmer switch. thjat's almost certainly it.

 

Alt issue is likely a poor battery connection, or poor fusible link connections.

Second the dimmer switch especially they will play up when spun to full bright position pull the illumination back 10% and bet it works perfectly.

it sounds like a bad connection under the dash, possibly a ground.

Edited June 17, 201213 yr by mikaleda

So I replaced the alternator, no changes there. Then I started looking at the illumination control module, replaced that guy and the dash lights all work like a charm. That must have been at least part of the issue. Not sure if the warning lights still glow as It hasn't been dark enough while I am working on it to tell yet. Thanks for all the help guys.