Troubleshooting temperature gauge reading low

[Roland Gendreau]

My engine temperature gauge normally reads about 120 degrees.  I changed the thermostat (160 degrees) and there was no change in the indicated temperature. So I am assuming either the gauge or the sensor needs to be replaced. 
Is there a way of determining which one to replace except by trial and error? Fore example, if I know what the resistance of the sensor should be at ambient or 160 degrees I could determine if the sensor was off.

Thanks

Roland

[Craig Illman]

One more thing, besides the sensor and gauge. Check the ground to the gauge as well.

[Ron Hill]

Roland : Go to Kubota and buy a new sender.  About $15 !!

[Roland Gendreau]

Does anyone have the Kubota part number for the temperature sensor for an M25XP? 

[Stu Jackson]

Roland, the C34 Tech wiki might help:

http://www.c34.org/wiki/index.php?title=Manuals

There's a Kubota manual listed.  I have't looked, you might give it a try.

[Roland Gendreau]

Thanks Stu. I had already looked through the Kubota parts manual and there is no coolant temperature sender listed.

[Ron Hill]

Roland : You might have to go to Westerbeke for a temp sender.

A thought

[Roland Gendreau]

Yes, that is why I was looking for some information that would allow me to check its calibration;  buying it through Westerbeke is an expensive way to troubleshoot it.

I know that the resistance through the sender decreases as engine temperature increases.  Knowing what the resistance should be around 160 degrees would be good information.

[lazybone]

Try pulling out the sensor and cleaning the rod that extends into the engine.  Sometimes they get encrusted with crap and it effects the signal res.

Typically you should see about 150 - 250 ohm difference from cold to hot.

[Roland Gendreau]

I am adding some information from my temperature gauge troubleshooting to help out the next guy with this problem.

I found that the resistance thru my sender is open circuit at ambient conditions, whereas it should be around 900 ohms.  When I ground the sender lead to the engine block, the gauge reads full scale high, which is the expected response.  

There is a sender made by Sierra (part number TS26611) that looks identical and costs about $25 (vs nearly $90 through diesel parts suppliers).  You can get the Sierra sender thru WM, Jamestown Distributors and other on line suppliers.

The Teleflex temperature gauges many of us have require a type D sender, which has a resistance range of 240 to 33 ohms over the temperature gauge span. The Sierra sender is a type D so it is compatible with the gauge. It has a slightly longer 1/4 inch NPT threaded section and the temperature bulb length is the same as the OEM sender. So it physically fits fine.

 I will provide feedback on its performance when my boat is launched next week but I expect it will work fine since it is physically and electrically compatible.

[Roland Gendreau]

Just a note to close out the thread.   

The Sierra temperature sensor works perfectly. With a 160 degree thermostat installed, the engine temperature gauge reads just slightly higher than 160.  There is no need for anyone to pay $90 for a sender from Westerbeke when the Sierra sender is a perfect substitute at cost of around $25.

[Stu Jackson]

Alternative source for gauges ---

http://www.sailnet.com/forums/electrical-systems/139490-amega-gauge.html