Hi again,

Against my better judgment, I continue to own a 98 Blazer.

Don't get me wrong, I actually like the truck - in between the various and numerous problems it has, I like driving it, and it has lots of space inside which is handy with a family. But, we recently replaced the tranny, and most recently we replaced (for the third time) the fuel pump - not inexpensive fixes. But this is not the current problem. This one I think is pretty minor, but I thought I'd ask here.

The battery was dead the other morning (not surprising, it wasn't holding a charge very well recently and was about 5 years old) so I bought a new one and replaced it. When I started up the vehicle, the temp gauge pointed straight south (6 o'clock), like it lost the will to live. All other gauges are fine, and the vehicle is running fine, but I'm wondering if this is more likely just the one gauge, or if a sensor is gone. I really don't want to have to go in and fiddle with the cluster just to replace a single gauge.

What would I check first to see if it's the sensor or the gauge?

Cheers,
Grant

 

OK, while I'm waiting for someone to weigh in, I've looked around a bit - from what I've gathered, I would guess that it's the coolant temp sensor that needs to be switched out. But, I'm not certain how I would test that first to see whether it's the sensor or the gauge that's faulty. Anyone have any suggestions?

Thanks.

 

Analog gauges work by applying a voltage to the gauge, the voltage regulates the gauges position.

I'm guessing you could measure the voltage at your gauge and compare to that of a known working gauge while both vehicles are at operating temp. Same/similar voltage = your gauge is bad. Drastically different voltage = something else down the line is bad.

 

Thanks for the suggestion - go figure - suddenly a couple of days later, the temp gauge starts to work again, all by itself.

I guess I shouldn't be surprised. About a month ago, I was getting the check engine light registering a p0452 that would go on and off by itself, then the ABS light was going on and off about a week after that.

Apparently, I have electrical gremlins.

Cheers,
Grant

 

The gauges in your truck are controlled by the PCM. The resistance of the temperature sensor varies with the coolant temp. The PCM senses this by applying power and ground to the sensor and reading the return voltage. It then sends the signal to the gauge cluster to be displayed.

You could have an intermittent fault in the wiring to/from the sensor, but this would typically trigger a code. A full feature scan tool will be able to monitor the ECT sensor readings and could be used to determine if there are drop outs in the readings.

The gauge cluster could also be going bad. They have been known to have bad solder joints that could cause an intermittent condition. Next time it happens, smack the top of the dash and see if it has any affect on the condition.