Coolant Temp Needle way off (Page 1/2)
Rdy4takeoff MAR 15, 05:02 PM
Hello,

I took the dash off and gauge cluster to clean. When I reinstalled I noticed the Coolant Temp Gauge Needle pointing up! When I was cleaning I noticed the needls on the speed moving around etc. Did this needle just get stuck up and needs a gentle bump down?

Thanks
1985 Fiero GT MAR 15, 06:22 PM

quote
Originally posted by Rdy4takeoff:

Hello,

I took the dash off and gauge cluster to clean. When I reinstalled I noticed the Coolant Temp Gauge Needle pointing up! When I was cleaning I noticed the needls on the speed moving around etc. Did this needle just get stuck up and needs a gentle bump down?

Thanks



I've had that problem, bumping it back down will fix it, the early gauges don't reset to zero automatically
olejoedad MAR 17, 08:20 AM
Full right, as your meter shows, indicates an open grounded circuit.
Chances are that the plug on the right side of the cluster has the flexible circuit board delaminated and is causing the problem.

[This message has been edited by olejoedad (edited 03-19-2024).]

1985 Fiero GT MAR 17, 09:54 AM

quote
Originally posted by olejoedad:

Full right, as your meter shows, indicates an open circuit.
Chances are that the plug on the right side of the cluster has the flexible circuit board delaminated and is causing the problem.



No, the needle only travels between minimum and maximum on the indicated gauge electrically, through the range of its signal, if the needle was physically bumped, or it got the signal for full temp repeatedly on and off a few times without time for the needle to return to the off position, essentially ratcheting the needle up like that. The second gen instruments have much more range and that could be what you said, but the 1st gen instruments can get stuck like that relatively easily.
olejoedad MAR 17, 03:19 PM
The needles can get stuck, but full right is an open a grounded circuit on all Fiero temp gages.

[This message has been edited by olejoedad (edited 03-19-2024).]

1985 Fiero GT MAR 17, 03:34 PM

quote
Originally posted by olejoedad:

The needles can get stuck, but full right is an open circuit on all Fiero temp gages.



Yes, but not that far full right, on the early gauges they physically cannot go that far unless physically bumped up there, late gauges maybe have the electrical control to go up there, but early gauges, of it is that far up, it is entirely physical. Early gauge range, full left to full right is exactly what is numbered, it can't go below the lowest number, and can't go above the highest number, very small range, do if it is past that range, it was physically pushed up there, and simply rotating the needle back will fix it, the early gauges also don't return to zero when turning off the car, which doesn't help.
FieroMark MAR 19, 06:24 AM
I found that the initial hard swing on start-up, due to the "unusual" wiring of the gage circuit that puts full voltage during crank, got my needle stuck in that exact position. All I had to do was remove the gage to allow the needle to return to the normal position in order to fix it.
1985 Fiero GT MAR 19, 07:52 AM

quote
Originally posted by FieroMark:

I found that the initial hard swing on start-up, due to the "unusual" wiring of the gage circuit that puts full voltage during crank, got my needle stuck in that exact position. All I had to do was remove the gage to allow the needle to return to the normal position in order to fix it.



That could also cause it, especially if you pressed the key 2+ times in quick succession, are your needless yellow or orange, because orange is much more likely to get stuck from physical issues, and electrically "ratcheting" up when the signal is applied on/off/on very fast, yellow needles, are more likely to be an electrical fault or bad signal then being truely "stuck" up there due to there increased throw and the way they return to zero.
olejoedad MAR 19, 08:40 AM
I have corrected my two previous posts in this thread.

The temp gage will deflect full right when the circuit is grounded.

Thie mistake in the OEM wiring that causes this is due to the gage lead being connected to the ignition switch terminal G2 in the KEY ON and START positions. The situation can be easily corrected by clipping the two small diameter green wires on this terminal and connecting them together.

There are also other methods for eliminating the gage pegging AND showing the HOT light at BULB TEST/START.

I apologize for the previous bad information which has been corrected.
Vintage-Nut MAR 19, 09:27 AM

quote
olejoedad:
There are also other methods for eliminating the gage pegging AND showing the HOT light at BULB TEST/START.



FYI - One method is this link - Coolant Temperature Gauge Information and Fix/Repair....
https://www.fierofocus.com/...osails/tempgage.html

------------------
Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles