Whenever I turn on my truck, the temp gage needle immediately jumps to the center of the gage. It doesn't matter if the engine is hot or cold. I did unplug the connector from the sending unit but the needle still jumped to the center when I turned the key. Maybe this wasn't the correct way to see if the sending unit was bad? Did anyone else ever have this problem? I had written about this a couple of years ago but never got an answer. I would really like to get this fixed before I really screw things up if I have an overheating problem some day.

"Jumps" as in a springy action or as in rises quickly to center? Mine always has done the latter, even in cold weather. It's a little slower under, say, 10 degrees F, but at that point I'm usually plugging it in, so it really races up to temp. It definitely let me know when it started to overheat after the headgasket went, too.

You could git something like the Ultra-Gauge to monitor yer vitals on the truck including the water temp that the ECU sees instead of the analog gauge on the cluster.

It jumps as in instantly when I turn on the truck. The needle goes from the far left position to dead center on the gage in less than a second.
The Ultra-Gage is a great idea. I didn't know that they were that inexpensive. I thought about doing something like that a couple of years ago but everything was too $$$.
Thanks!!!

Did you pull the cluster out at any point before the temp gauge went bonkers? Maybe a wire got pinched or something?

Did someone install an alarm system or some sort of accessory lately?

I didn't use the Ultra-Gauge windshield mount...I made my own from a wire hanger, a screw and washer. I guess you could use the factory screw fer the cluster if you don't want to put a hole in yers... <img src="/forums/images/graemlins/wink.gif" alt="" />

No, nothing was taken apart or added before I started having problems. If I remember correctly, before it completly went bonkers it would work OK on cool mornings but then during the day when it was hot out it would make the needle jump right away. WIERD???? It seems almost like a short. I tried tracing some wires but couldn't find any that were bare or pinched. Nice pics. If I don't come up with a solution to fix the gage, I will definately get a Ultra-G.

I have a scangauge 2... what is the difference between the 2?

I guess you could always git another cluster and see if that fixes it or not. <img src="/forums/images/graemlins/wink.gif" alt="" />

The difference between the SGII and the UG is that the UG costs less, gives you more information on the screen at a time, gives you 3 screens of information to scroll through, and has audible/visual alarms.

The only thing I don't like about my UG is that it's not seeing the voltage and you can't program it. Although...I haven't been able to git any custom programming fer the SGII to work on my T-100. <img src="/forums/images/graemlins/frown.gif" alt="" />

Fer example...I was able to put both O2 sensor readings on the UG and see that the front sensor was slow to respond after the engine was warmed up and then shut off. It used to take about 5-10 minutes after that fer the system to go back to closed loop. After I replaced the both sensors, it only takes less than a minute to go to closed loop. <img src="/forums/images/graemlins/smile.gif" alt="" />

These are the (33 plus the 2 UG ones) gauges Ultra-Gauge sez it recognized on my 1998 T-100 SR5 2WD auto...not sure what it will come up with on the other T-100 year groups.

* Open/Closed Loop Emissions Status
* Percent Engine Load
* Engine coolant temperature
* Short Term Fuel Trim Bank 1
* Long Term Fuel Trim Bank 1
* RPM
* MPH
* Ignition Timing Advance
* Intake Air Temperature
* Mass Air Flow Sensor output in grams/sec
* Absolute Throttle Position Percentage
* Bank 1 Oxygen Sensor 1 Voltage
* Bank 1 Oxygen Sensor 2 Voltage
* Mass Air Flow 2, Calibrated/Calculated
* Instantaneous Miles Per Gallon (MPG)
* Average Miles Per Gallon (MPG)
* Average Miles Per Hour (MPH)
* Average Gallon Per Hour (GPH) - general
* Run Time - general
* Distance - general
* Fuel Used - general
* Instantaneous Gallons Per Hour (GPH)
* Fuel Tank Gallons Remaining
* Distance to Empty(DTE)
* Time to Empty (TTE)
* Volumetric Efficiency (MAP vehicles only)
* Average MPH - trip
* Average MPG - trip
* Fuel Used Gallons- trip
* Average Gallon Per Hour (GPH) - trip
* Run Time -trip
* Distance - trip
* Oil Distance
* Service Distance
* UltraGauge Temperature

Did you unplug the sender or the sensor to test it? One is for the dash/gauge, one is for the ECU and they are in different locations.

I checked the sensor behind the timing belt cover on top of the engine. I am looking at my Haynes book and it is calling that one the "Engine Coolant Temp Sensor". That is the only one that am am seeing in the book. Is that the one for the dash? Where is the other one located? One thing that I hadn't noticed in the book before is a chart for resistance in ohms depending on the coolant temp for this sensor. I wish I would have seen the chart while I had everything apart. I should have my Ultra-Gauge tomorrow, but it would still be nice to know what my problem is.