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Mechanical temp. guage problem


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:classic_angry:Mechanical temp. guage. The problem: temp. guage doesn't work reliably. Tested guage off engine..works. Reinstalled sender/sensor into engine(it's at one of the lowest parts on the block) no air pockets. When reinstalled the guage doesn't work unless you wiggle the sensor/sender and then it will sometimes. I have tried two other guages of similar design with exactly the same results. This is making me crazy. Any thoughts?

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According to the info you gave, partitioning leads this to be a wiring issue or a sender issue. You have eliminated gauge as an issue.

 

Have you tried using something like a power probe or similar to send power from the sender pigtail back to the sensor and see if that works consistently or interim? The observation that it works while wiggling is implying it's a mechanical break in connection in one of the components affected the movement. 

 

Alternatively, I'm not sure what engine you have but my block temp sensor isn't used. I utilize the one that sits in the thermostat housing. 

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Is this a mechanical temperature gauge with a temperature bulb and non removable capillary tube connecting it to the gauge, or an electrical sensor that connects to the gauge with wires?  Very different animals with different things to check.  

 

-John

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Does it affect the reading if you wiggle the end of the tube at the gauge, or jut at the sensor bulb?  Given that you have multiple gauges acting this way -- fine out of the car, but intermittent when installed -- it makes me wonder if the capillary tube is being partially pinched or kinked with it's current routing?  

 

-John

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The reading at the guage is only affected by wiggling the the capillary tube at the sensor bulb at the block connection. I thought at one point that I had over tightened the bracket holding the guage at the dash  and distorting the guage face and binding it up but...no.

What is truly boggling is the fact that if you remove the sensor bulb from the engine and put in a pan of hot water it works as it should. I will add that prior to using this new set of guages the car had an old set of S/W guages and the water temp worked fine. The S/W sensor bulb mounted on a flat surface as opposed to the new sensor which mounts on a tapered face. The new fitting for the sensor has a tapered face.

I'm a reasonably skilled mechanic but this "problem" just doesn't make any sense to me, it's seems illogical.

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Is the sensor actually in the coolant? or in a well? You should not be able to wiggle the sensor installed directly in the coolant without it leaking. If it is in a well then perhaps wiggling it would cause contact with the well to effect the reading.   And if your dash is not sufficiently grounded and using the capillary as a secondary ground there could be some contact hear that could effect the reading.  All will be clear on this perplexing problem when the solution is found.             john

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