Temp Gauge

1989 GT

Swapped out the 85 speedo for a FM 140 and, while I had the cluster out, I bumped the temperature gauge needle and it spun around 360+ degrees. Stupidly I didn't think to spin it back or do anything with it. Now, when it's running, everything seems normal but, when I shut her off, the needle pegs all the way to the top, almost not visible behind the dash cover(?).

I know some gauges stay where they are when you shut off and some go back to "zero". Crazy as it seems, I've been driving this car for 34 years and I can't recall what the temp gauge normally does when the engine is shut off. Only thing I'm sure of is that it should not peg out all the way to the top. I'm assuming that it is going back to wherever I left it after I bumped it.

so, the Qs are:
Where should the temp needle be when everything is shut down? stay where it was when running or back to "zero"?
If "zero", is it as simple as moving the needle back to wherever that is and is that "130" or somewhere else?

thanks for any help
 
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I have a 91 LX and I just returned from a drive so I looked at the stock temp gauge for you and mine remained where it was when running and did not drop down to zero…..
I then put the key back in and turned it to the start position to see if it would drop down or remain. The gauge started to slowly move down toward the bottom but when I pulled the key back out it stopped again where it was….
So if my gauge is working as it should, the answer to your question would be that when the car is shut off the stock temp gauge remains at the temp it was at when the car was shut off and does not drop to zero.
Hope this helps…
 
thanks for the replies...

that actually jogs memory. I'm in agreement that the temp stays where it is when you shut it off.
I was thinking I could go back in and put the needle to 130 and it would be good but I'm not sure that would actually fix it.
 
Have had some time to drive the car since this issue came up and noticed something that, at least to me, seems strange regarding the temp gauge.

I always run my parking lights, even during the day light, it's second nature. On occation second nature fails. The other day I never turned them on and when I shut the car off the temp gauge stayed where it was. That was when I noticed the parking lights were not on so, out of curiosity, I turned them on and the temp gauge pegged out all the way to the top.

So, as long as the lights are not on, the gauge stays at whatever the operating temperature is at the time of shut down. Only with the lights on does it go to the top as stated earlier in the thread.

Strange or no?
 
I have frequently noted that a lot of the foxbodies i've driven over the years had had a small rise on the coolant temp gauge depending on if the lights are on or off. It's usually been very very small, but enough to be noticed.

If yours is pegging out, that's definitely abnormal.
 
Yes, I have noticed the small movements with the lights as well.

I don't recall the pegged out condition before I bumped the needle when I recently had the cluster out. Maybe it's always done it? I just don't know / remember.
 
The temp gauge int he cluster only has three connections.

12v power source
ground
single direct connection to the coolant temp sender on the driver side front of intake.


My thought it that a voltage drop may cause the reading of the resistor by the guage to change which results in the change as you turn headlights on/off. However, for it to be that large would require a significant voltage drop. Whats the state of the charging system? Are you able to maintain 12.6V+ at idle?

Could also be a loose or dirty connection somewhere increasing the sensitivity to slight (normal) voltage drop. May want to take a little sandpaper to the temp sender and ensure a clean connection