temp gauge moves a lot

[dwarf]

My temperatue gauge will move up to the top of the O in Normal, mostly during idle. While driving the needle is around the A. Sometimes the gauge will go from the bottom of the temp gauge and up to the top of the O and then back down within seconds.

I was wondering if there was a reason for the temperatue guage fluctuation?

 

[hawkeye18]

sounds like a bad connection at the sender gauge. It's just a single-wire push-on connector. It's right in front of the thermostat (or to the left, if you're looking at it from the driver's side) and down a little. Take it off, clean it out with some electronics cleaner or whatnot, and put it back on... see if that helps.

 

[Ishodu]

Sounds quite "NORMAL" to me. The gauge seems to have a lot of travel for a small amount of change in temp.

 

['94SHO]

The whole range of the gauge is only +/- 15? degrees.. Not a big deal.
That is why the whole sweep is marked normal. But, if this just started happening, I would also be concerned. The sending units are a service item.
They do go bad occasionally. Of course, check your connections . Are you
losing any coolant? How old is your thermostat?

 

[rubydist]

Whenever I've had that experience, it was the thermostat starting to stick. Pretty soon it wouldn't open or wouldn't shut, and I was changing it. I'd say that's the most likely reason for your symptoms.

 

[dwarf]

It's been like this ever since I got my car. 1994 MTX 117k. I didn't know the whole range is only a 15 degree difference? So if my car runs at the top of the O regularly(which it doesn't) it would be alright?

 

[ultimatesho]

my 92 dose this to.....crusin itll stay around the A and L , but when i hit town traffic and start stoppin alot itll go to rite around the O

this worried me at first so i replaced my sendin unit and thermostat......changed nothin........so i dug a little deeper and found out this is fairlly common with SHO's

 

[Eric VerValin]

http://www.shoforum.com/showthread.php?t=83717

Guess mine is different then.. or broken sounds like..

 

[itwonder]

SHO temperature needle does move around more than is typical for other cars. But a common problem is a radiator cap that has a small pressure leak. The cap will appear to hold pressure on the car, but will fail the test if you test it with a radiator pressure tester. Cheap enough to replace the cap. BTW, often blamed on thermostat when it's actually the cap.

 

['94SHO]

Yup, lots of places will pressure test the cap for free.. PEP Boys for one.
Or, just replace it to take it out of your equation.

 

[1995mtxsho]

Air in the system will also cause this. Radiator cap and leaking hoses are the most common causes.

 

[fitefanSHO]

SHO temperature needle does move around more than is typical for other cars. But a common problem is a radiator cap that has a small pressure leak. The cap will appear to hold pressure on the car, but will fail the test if you test it with a radiator pressure tester. Cheap enough to replace the cap. BTW, often blamed on thermostat when it's actually the cap.

My cap was junk so I replaced it last week. The needle still gets around tho and my thermostat and coolant is nice and new with no leaks in the system.

Feels NORMAL to me.

 

[93rev2sev]

Weak waterpump or maybe the fans not kicking on?

 

[AREA 91]

my 92 dose this to.....crusin itll stay around the A and L , but when i hit town traffic and start stoppin alot itll go to rite around the O

this worried me at first so i replaced my sendin unit and thermostat......changed nothin........so i dug a little deeper and found out this is fairlly common with SHO's

Both of my SHO's are like this. They both have new sensors. I have triple checked with my infared temp gun, and it's ok.

 

[yamahaSHO]

My SHO does this and it follows my AutoMeter gauge as well. I have all new sensors, water pump, thermostat, and dual core radiator.

 

[SHOZ123]

The total range of movement depends mainly on your t-stat rating. The total gage NORMAL range is ~160F to ~230F. The low speed fan(s) come on at 215F, off at 210F.

So if you have a 180F t-stat instead of a 192F t-stat this will add 12F to the sweep.

If you are moving and the fans don't need to be on then the gage will read lower. If in traffic and the fans are controlling the temp then it will be considerably higher.

From the manual...............


The cooling fan is controlled during vehicle operation by the Constant Control Relay Module (CCRM) 12B577 and Powertrain Control Module (PCM) 12A650 which will energize the cooling fan under the following conditions:

Cooling fan is turned on for the 3.0L SHO and on at low speed for 3.0L, 3.2L SHO and 3.8L if:

a. Engine temperature is higher than normal. (Fan starts running at 102°C (215°F) and stops running at 99°C (210°F).

b. A/C is on and vehicle speed does not provide enough natural airflow. (Fan starts running at speeds at or below 69 km/h (43 mph) and stops running at 77 km/h (48 mph).

On 3.0L and 3.2L SHO engines with ATX, low speed cooling fan motor operation is achieved by using a dropping resistor in series with the motor/motors.

The 3.8L uses a dual winding fan motor in which low speed motor operation is achieved through the low speed motor winding circuit (no dropping resistor).

Normal operation and cycling of the engine cooling fan will cause the temperature gauge indicator to read between the mid-point and upper portion of the temperature gauge scale. The slightly higher indicator reading will return to mid-point when fan operation begins.

Cooling fan will run at high speed if:

a. Engine temperature is higher than desirable and fan has been operating at low speed. Fan starts running at high speed at 110°C (230°F) and stops running at 107°C (224°F).

 

[dwarf]

Adding coolant to my coolant reservoir made my car so much cooler. It was damn near dry. It barely even reaches operating temperaute if i stay on the freeway now

 

[93rev2sev]

Then you have a stuck open thermostat.

 

[dwarf]

I checked my coolant and its back to none. I don't think it's burning this much coolant, hopefully it's a leak? I added it into the resorvoir a few days ago and now it's empty.

 

[hawkeye18]

Coolant really likes to get out at the seam between the radiator and the endtanks. The endtanks are plastic, and the metal radiator shrinks when it gets cold... you can see where this is going. Putting a bead of RTV around the endtanks can help fix this. JB-Weld is an alternative, but since JB-Weld doesn't flex (and the metal radiator does!), that can solve issues. You can also re-crimp the endtanks on, and that can help.