The Pegging Temperature Gauge Fix – Reprinted from the Michigan Fiero Club Newsletter Fiero News November 1998 – Volume 5 Number 11
Thanks also go to NIFE member Tyrone Johnsen who recently submitted this same tech-tip.
The problem lies in the wiring...
The wires you need to be concerned with are located on the steering column and on the back of the IP Cluster. I am going to give details on removing everything so you can find things easier. This process will take a couple of hours, but it is not difficult. Also, if you wish, you may solder the connections. First you will need to remove the trim panel under the steering column. There are four 7mm screws, two of them screw into the bottom of the IP Cluster (Figure 1 - A screws). Next remove the two 10mm screws on the bottom of the IP Cluster (Figure 2 - C screws).
Next using a T-15 Torx bit, remove the five screws that hold the back trim panel of the IP Cluster, there are also two 7mm screws on the bottom of the IP Cluster (A total of 7 screws hold this panel on). (Figure 2 – B & D screws). Using the T-15 torx bit remove all the screws from the headlight switch and trunk release panels (four screws per panel), note the location of the longer screws (top half of panel). Slide out the switches and unhook the connectors.
Next locate the last two 10mm bolts that hold the IP Cluster to the dash (Figure 2 - C screws). They are located inline with the steering column. The IP cluster will be "loose". Begin unhooking the 3 wiring harnesses from the IP Cluster. There are 2 connections on the driver’s side and 1 vertical connector on the passenger side. Two of them have tabs at the ends that need to be squeezed to release the connector and the third (located on the bottom of the IP Cluster) has a tab in the center of the connector. Remove the various wiring and clips so you will be able to remove the IP Cluster, which will be lifted over the steering wheel and set aside.
Now you will be able to see a lot more. The first wire you need to get to is the Ignition Switch Connector. It is located on top of the steering column and is two pieces (Blue and Black connector) (Figure 3 - 8). This may be hidden by another larger flat connector (on the bottom of the steering column if you look from the bottom). You will barely be able to see the connector from the top, as it is hidden by the metal support for the steering column. Locate the two Light Green wires that are attached to the black portion of the connector (Figure 5 - G1).
Now for the wiring fix, you have two choices… Remove the terminal from the connector or cut the wires. (Note: The original Wiring is shown in Figure 6).
Option One: Cut the wires (Figure 7):
Cut the two light green wires and splice the two ends together (splice the two ends from the wiring harness, not the ones from the Ignition Switch Connector, as show in Figure 5) Next attach a similar size wire (Label "N", Figure 5) to one of the light green wires from the black connector. With electrical tape, cap off the other Lt. Green wires from Ignition Switch Connector, as you will not use this wire.
Option Two: Remove the terminal from the connector (Figure 8):
Unhook the Ignition Switch Connector (Black) from the harness (on top of the steering column). Use a small screwdriver and stick it in next to the G1 terminal to bend back the locking flange. Pull out the terminal, with the two wires, from the backside. Tape up the exposed connector, as you are finished with these wires. Go to the local auto parts store and buy a connector like you just removed (it is a standard connector). Crimp the connector to a new piece of wire (Figure 6 - N). Push the connector into the Black Ignition connector and make sure it is locked in place and plug the black ignition connector into the harness on top of the steering column.
Now for the final part of the fix...
Take the new wire "Wire N" and run it up to the IP Cluster Connector. Locate the IP Cluster Connector, which was originally on the passenger side of the IP Cluster, in a vertical position. Look for a Dark Green wire going to slot C13 (Figure 4) (NOTE: the Dark Green wire may go to slot C17 on your Fiero - Look for the Dark Green Wire). Splice your "Wire N" into the Dark Green wire (as shown in Figures 7 & 8). You can cut the Dark Green wire in half and then use the crimp connectors or just peel away the insulation and wrap "Wire N" around the bare part of Dark Green wire. Insulate the connection with electrical tape. Congratulations! You are done with the conversion. Replace the IP Cluster and before buttoning everything back up, double check to make sure you temperature gauge works (remember it will no longer jump to the top on startup) and also your temperature warning light should light up when you are cranking over the engine (this is the factory test mode).
Special Thanks to:
Oliver Scholz (email@example.com)
And the Fiero Mailing List
(Copyright 1998, Michigan Fiero Club, no part of this document may be reproduced without written permission of the Michigan Fiero Club. The only exception is for non-profit organizations, but they must acknowledge the Michigan Fiero Club as the author of this article)