Jessa

A couple weeks ago the upshift light in my 84 came on when the car was started, and stayed on for the whole trip - even in neutral, reverse and 5th. After an hour of being parked, it was normal the whole trip home. The problum didn't come back until yesterday. Now, about every other time I start the car, this light comes on and stays under all conditions. The other half of the time its fine. I tried telling the shark that we can't upshift to a higher reverse gear, but it just won't listen!

Ted928

This is OT but I get the biggest kick out of the up-shift light. It is opposite to all the other cars I have driven. If you are driving the 928 less than wide open it says UPSHIFT, I've got plenty of torque. But if you decelerate it says "this gear, or any gear for that matter is fine".
Most cars (low power, low gearing) always tell you to up-shift when you let off the throttle - not the 928. Neat.

Jessa

Anyone got a clue how to fix this? Or at least possible causes?

WallyP

This is a fairly complex little system, not just a vacuum-operated light. The wiring is complex, and goes thru quite a few connectors. The wiring diagrams for the '84 are totally useless, so we have to look at the '85 and '83 diagrams and hope that the '84 is similar.

The write-up for the upshift indicator starts on page 90-53 in Volume VIII.

The tach must be working, the temp gauge must be working, and the speedometer must be working. The injection time signal must be coming in from the LH ECU.

Basically, the manual says to check all of the connections and signal paths, and if all are good, the tach must be replaced.

Your problem may well be a bad connection - but the only way that you are going to find this is to have the wiring diagrams and the Factory Shop Manual and spend a lot of time checking. No easy answer on this one, I'm afraid.

Greg86andahalf

Jessa,

I sent you some info from the manuals to the email address on your email link.

It steers you towards a test point which will give an indication of wheather the signal is reaching the cluster. If you can do this test, it will narrow things down a bit. If taking a WAG, the PCB and connections at the pod may be a good place to start.

Does you tach malfunction at all?

Greg

Jessa

Thanks Greg and Wally. Since my tach, speedo and temp gauges appear to be working, I'm going to start checking the connections. A loose connection would also explain why it only happens intermittently.