|Tech Tip: Strange Gauge Behavior in a Late (Series 2) 944.
I wrote this article after having some strange readings on my instrument cluster - to include: fuel gauge reading ' full when I just filled the tank, voltmeter constantly reading 12 volts.
My initial thought was a bad ground (especially for the voltmeter) and a bad fuel sending unit. However, after replacing some burnt out instrument lights, I found a fix that took care of them both - for no cost at all!!!
WARNING/DISCLAIMER: This procedure involves removing your instrument cluster and manipulating some of the electrical contacts on your gauges. If you don't know what you are doing, or are unfamiliar with proper electronics safety (static charge etc..) DON'T DO THIS PROCEDURE! The instrument cluster is HIDEOUSLY expensive. Pelican Parts has replacement VDO Gauges, but the circuitry is a dealer only part - and they only sell it as a whole assembly - prepare to spend in the neighborhood of $1500 or more if you screw up. Of course, if you screw up, I am not responsible, you have been warned.
24mm Socket (for steering wheel)
5, 6, &7 mm sockets
metal polish (Never dull works great)
alcohol wipes (or alcohol and q-tips)
Light bulbs (available from Pelican)
Personal grounding strap (Highly recommended)
Beer or other favorite tasty adult beverage
1. Disconnect the negative battery cable
2. Disconnect the fuse for the instrument panel (yes, I know, paranoid, but better safe than sorry)
3. Remove the steering wheel
4. Remove instrument panel trim piece
5. Unscrew the instrument panel
6. Carefully disconnect the three cables from the instrument panel.
7. Remove the instrument panel from the car
8. Take the panel and your tools to a clean, dust free area where you can sit and work.
Procedure, Instrument panel tune up:
1. Place the panel face down on a padded surface (clean towel works well)
2. Ground yourself using a ground strap.
3. If you have them, now would be a good time to change out all of those instrument panel bulbs.
4. Now, look at the back of the panel - on each side, where the combo gauges live, you see 2 black football (or rugby ball if you are in the UK) shaped objects with a brass nut in the center. Loosen these with the socket. After you have gotten the nut and washer off, lift the football shaped thing off of the circuit board. - these are the main electrical connects for the combo gauges.
5. Clean the nut, washer, and the brass posts, as well as the threaded post sticking out of the circuit board with metal polish - then wipe down with alcohol to remove any residue.
6. Reassemble, making sure the nut is SNUG (DO NOT OVER-TIGHTEN!!!!!)
7. Repeat for the other footballs.....
8. You will also see a few SILVER, FLATHEAD, screws - snug these up as well, once again, do not over-tighten.
9. Clean the cable attachment points with alcohol
10. In the Haynes style, installation is the reverse of removal.
Michael Van Bibber (AFJuvat)
Page last updated: Mon 5/25/2015 02:20:52 AM
Pelican Technical Article:
Solving Strange 944 Gauge Problems
Michael Van Bibber
Porsche 944 (1983-89)