The previous owner of my 86 GT hates me. At some point, they hotwired past the dimmer transistor (.8 GRN/WHT => .8BRN behind the dimmer switch), and did SOMETHING to disable the courtesy chime. I've had a couple dead batteries from leaving the parking lights on over the years, and I want to get the car toward factory new function, so I decided to try to fix all this. The first one was easy (I thought). I deleted the hotwire and repaired the GRN/WHT wire to its original run. Everything worked! The dimmer could go from nice and bright gauges to all the way dark. I mostly drive during the day with lights on only for rain, so I left them nice and bright for now. About a week later, I'm taking off at night, and as I back out of my parking space, all the interior lights blink out. By the end of my long driveway, they pop on one more time and blink out for good. Loose wire, I thought, must have bumped something or tugged too hard to make my splice under the dash.

Later this week, I see the temp gauge has given up. Car off, needle in rest position on the left, car on, needle at exactly 100° and stays there.

Today, I open it up and start testing things.

TEMP GAUGE:
Service Manual pp. 8A-80-0
-I corrected the bulb test wire years back to prevent gauge or needle damage, needle does not jump on TEST
http://www.fierosails.com/tempgage.html
-Followed thread:
https://www.fiero.nl/forum/A...110502-2-105462.html
-Sensor terminals are a little crusty, but the connectors aren't cracked.
-After scratching a bit, ohmmeter read normal range for just having been driven.
-Shorting connector wires to ground does NOT peg needle to right, but does turn on temp warning light.
-Turn signal makes tach needle dance by about 1000 RPM at idle with A/C on, even after ground G201 cleaned (see below)
Conclusion: Wiring problem! Where? There was a delay of weeks since I'd touched anything til the gauge started acting up.

LIGHTS:
Service Manual pp. 8A-114-0
https://www.fiero.nl/forum/Forum2/HTML/140099.html
https://www.fiero.nl/forum/A...050119-2-054366.html
-All exterior lights function properly
-No fuses blown, no bulbs burned
-Continuity on BRN, GRN, DK GRN/WHT
-12V in and out of transistor at no dimming (car off, park lights on)
-Continuity on GRY from Gauge light fuse (back of block) to dash plug
-Cleaned ground G201 (ring connector broke at a touch, replaced with new ring connector)

CHIME:
Service Manual pp. 8A-77-0
-Stared at the wiring diagrams
-Looked for any missing or spliced wires
-No idea where to start.

I'll do the easy one. Under the passenger side dash, is the door chime unit installed? This is the unit...the blue box:


People get annoyed and unplug the box.

[This message has been edited by IMSA GT (edited 10-06-2018).]

Aaaand, ordered. Hey that WAS easy! Thanks IMSA. Glad I hadn't spent a ton of time on that one yet.

May I chime in here? I am having similar issues with the oil press. gauge swinging wildly side to side then settles a bit then does it again.
Any ideas Time Traveler or IMSA? This is '88 GT I just got last week. Don't mean to hijack this thread, just thought similar topic. Thank you for any suggestions.

88Fingers, check this thread:
https://www.fiero.nl/forum/A...020511-2-017164.html
Also, follow my fierosails link above to fix your temp gauge before it causes problems as well. Mind you, it's no guarantee, since I'm obviously having some different issues with that, but it's an easy preventative job. As a complimentary fix, I replaced the rotting air filter foam on my gauge housing using some a/c filter foam and double sided tape. Keeps the dust and rotted foam out of your gauge pod!

To the rest, still waiting on suggestions for my lights and temp gauge. Googling in the meantime has turned up nothing I haven't tried

Hey Time Traveler, thank you so much for the link and suggestions for other issues. I wish I could help you out but I am in a learning process myself for this stuff.
I am sure one of the guys will get you in the right direction. Thanks again.
PO put a new alternator on. Could it be a grounding issue?

[This message has been edited by 88Fingers (edited 10-08-2018).]

As far as I understand, a lot of things could be a grounding issue. It seems to be highly recommended to replace or add a second block ground strap, plus check and clean the grounds inside the car. See the link in my OP above regarding ground G201. There's another, smaller ground right there, too. See the below link regarding the block ground strap.
https://www.fiero.nl/forum/Forum2/HTML/043240.html

A bump before the weekend. I'm sure I'm missing something, but short of a gauge pod teardown, I'm not sure what to do.

It's very difficult to offer advice when a previous owner has modified the wiring. You could try posting pictures of any wires that don't look stock, and someone might recognize what to do.

A quick coda on a couple of these issues:
The blue door chime box was missing, the replacement will be arriving today. I haven't found any other modified wiring, so I'm ready to mark this issue as "fixed"

The temperature gauge is now functioning again. On the plug to the gauge pod (the horizontal plug on the LH side of the car, into the printed circuit), one of the pins was depressed slightly. I cleaned the pins, and gently pried this one back up out of the plug body, level to the others, to make good contact. I suspect the contact was poor to begin completely, and probably jostled loose as I moved things on the hunt for my lights problem.

That said, I'm still stumped on the gauge lights. As far as I can tell, the wires are currently in their stock configurations, albeit with a couple splices on wire to repair the damage done. I have continuity on all the components, I have cleaned and tested the headlight switch and rheostat rotor, and I believe I'm getting correct readings off of the transistor. However, I'm getting 0V off the two gauge light pins at the LH plug to the printed circuit. Given I have continuity off that same wire, that makes me think a short to ground, but I don't see where that could be going on, as that wire was undamaged and unmodified as far as I can tell.

Double coda, for those who find this thread searching on the same problem.

Turns out, the dimmer switch transistor HAD failed. I assume this is why the previous owner had it bypassed, and I don't know why it worked again (albeit briefly) after I un-bypassed it, but it did. It even flickered to life briefly after it died on me (post-wiring restoration), but it then failed to ground. I didn't interpret my multimeter readings off the old transistor correctly, and it wasn't til I read an article on transistors that I realized I'd screwed that up. So, I ordered a new transistor off Rock Auto for $20, and five minutes after I got it, all is as it should be. The tiny sun behind my gauges rises and sets at my beck and call!