I just bought an 85 SE in beautiful condition. The problems I inherited are in the instrument panel/cluster which I don't know much about:

-- Fuel Gauge - Occasionally works, currently shows 'uber-full' all the way to the right.
-- Speedometer - Bounces around +/- 10mph, but doesn't get above 30mph regardless of speed.
-- Tachometer - Works great!
-- Oil Pressure - All the way to the right off the gauge.
-- Temperature - All the way to the left off the gauge.

I've replaced (and verified) all fuses are correct. I've searched on these problems, and it doesn't seem like the 'pegging' problem, since nothing spikes up really high.

My question is... Where do I start?
Should I be looking to replace the instrument panel from a parts car? Track down wiring? Does anyone know a comprehensive source for wiring info on the cluster? I'm trying to get an idea what I'm getting myself into :-)

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-Ozi

Fuel gauge is most likely a bad tank sending unit

Speedo - beats me. Most likely a bad speedo

Oil Pressure Gauge - At the oil pressure sender - ground the center wire of the plug (key on engine off). Does the gauge swing to zero? If yes - bad sender. If not bad gauge or bad wiring.

Temperature Gauge - Find this temperature gauge/temp light sending unit. Key on ground each of the wires watching the dash TEMP light and the Temperature gauge. One should cause the Temp Gauge to peg hot. The other should cause the TEMP light to come on.



This is the temperature gauge sending unit. It has two functions. The wire that connects to the pin that is AWAY from the side notch is for the gauge. The wire that is close to the side notch is for the TEMP light (yes your Fiero has one).

Turn the key on but leave the engine off. Ground one of the wires. Then try the other. One should light the temp light. The other should make the temp gauge (or just pivot in your case) move. Then just make sure the wires are on the correct pins so the two devices work correctly.

Wow, thank you that's very helpful!
Where would you start out of these? I'm thinking the temp gauge is the most important (and relatively simple?)

Is there a guide to taking apart the instrument panel to test for 'stupid' things, like loose or tight needles?

Take off the panel under the dash and find the two screws that go up into the back cover of the dash and take them out. Take out the 5 (I think) screws that hold the back on from the top. They are torx screws. Then the back is off and you can reach most of the bulbs. If needed you can continue to remove the entire instrument cluster.

There is/was a technical problem with the temp sensor in Phonedawgz' picture. It seems the factory wiring was not right. Some cars have been modified to work 'properly' and some have not.

http://www.fierosails.com/tempgage.html

it is possible the printed circuit board on the back of the dash cluster has cracked and some of the lines/wires are broken and not making contact. I had an 80s TA that happened to I bought my oldest daughter, not a part you can buy I think anyway but a distinct possibility. to be sure use a test light on the back printed circuit board, or better yet a continuity tester, no power need. just check the lines in the board, is that a deceptive enough name for a flexible peace of plastic on these. sometimes the lines wear out over the decades or have been damaged by a PO removing and reinstalling the cluster or the repeated heat cooling from outside temps.

Steve

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Technology is great when it works,
and one big pain in the ass when it doesn't



Detroit iron rules all the rest are just toys.