Hi folks,

Last week during an engine startup during a cold New England morning, I noticed that my temp gauge spiked to the danger level within less than 1 minute of the engine running. I immediately shutdown the engine. I then re-started the engine and the temp was still running at max, but there was no heat coming out of my vents so I assumed it might be a false reading. I waited a few minutes, and started the car again. After a few minutes, the coolant temp climbed to normal operating temperature. This has now happened a few times over the past few weeks. I'm assuming I might have a problem with the coolant temp sender? Many thanks!

 

My gauge all of sudden went from indicating a proper temperature range to over half way on the scale and this occured after driving the car less than a mile. Changed the thermostat with a factory replacement and it reverted back to the normal range.

 

I believe normal operating range is 1/2 (middle) of the gauge reading. Also I don't believe my problem is thermostat related... even if my t-stat was faulty, it would not cause my coolant temp to spike to overheating indications on the gauge in less than 1 minute of start-up idle on a cold morning.

 

Also depends what series the car is. S4 has a full spectrum gauge and the S5 has a 3 pos gauge. Cold, warm and rebuild.

 

I have an S4 and 1/4th to 1/3rd range is normal but mine was indicating twice that because of my faulty thermostat and this occured within 2 minutes of a cold start. If you haven't replaced your t-stat in years what do you have to lose? Check the sticky thread at the top of this forum and download the S5 FSM and it will specify how to check for your problem.

 

Pull the thermostat out and put the thing back together without it. Then see if the problem comes back in the next few days. You can figure out what to do after that.

If the sensor wire touches gnd that will drive the gauge full range but it would only take about a half minute to do that if not less than that. Kinda hard for the water temp sensor wire to touch gnd though, unless it's really buggered up.

 

Hailers - thanks for the advice.. I'll give that a try! I guess it's also possible that the water temp sensor is faulty right?