Gauge false overheat?

[Steph]

Few weeks ago, my Westerbeke 13 guage said it was overheating...shooting to over 200. Water intake and output was good. I replaced the thermostat and then noticed that as soon as I turned on the engine, the guage instantly went to 250 (engine was still cold). Is this a sender or guage fault and which should I replace? My guess is it's the sender. Thanks for any advise. Steph

 

[jssailem]

Not sure what is proprietary with Westerbeke, but on my 4107 Perkins I learned the gauge needed to be tuned to the sender. That there was a certain electrical current generated by the bi-metal sender and to get a proper reading the gauge needed to be matched to the sender.

 

[kloudie1]

check the wire from the sender to the gauge.. I don't know what gauge you have but depending on the gauge, you could have either a short (in the wire or the sender) or an "open" (bad connection )
Usually, a short in the sender wire or the sender is the cause of the gauge reading instantly full scale.
http://www.jamestowndistributors.com/userportal/document.do?docId=842

 

[Bill Roosa]

The sender and gauge are just a temperature sensitive resistor and ohm meter with face designed to read in temperature instead of resistance. So, if the temp sensor is shorted (0 ohms) then the gauge will read full scale (hot or cold depending on how the resistor is designed to respond to changes in temp), same thing for a shorted or open wire....so I'm thinking the gauge is OK and the problem is the wires or sensor proper. Test the sensor by taking the wire off and measuring the resistance between the terminal and engine block. Should read somewhere around 220 ohms at cabin temp. Also test the wire between the wire end and engine ground. It should show very high resistance. If the sensor reads high or very low it is probably bad. make sure the sensor body and engine block have a good connection (0 ohms) and the threads are not corroded. If everything checks out and the wire has a high resistance it may be broken. If it has low resistance to ground then it is shorted somewhere probable around the engine where it is rubbing on something.
Good luck

 

[Steph]

Thanks! I'll check it out as suggested! Steph

 

[Steph]

Bill, by the way, I'm up at Burt Jabin's Annapolis. Thanks again! Steph

 

[Stu Jackson]

Thanks! I'll check it out as suggested! Steph

Teleflex has some pretty good troubleshooting info on their website, IIRC. Good luck.

 

[gettinthere]

My sender went TU a few years ago, Perkins 4.154. Buzzer kept sounding but the heat gun said all was good. Finally removed the wire to make port without the noise and ordered a new sender.

 

[Terry Cox]

Ditto here. Last summer in the San Juan Islands we headed out under power, no wind. Glanced over at the engine temp gauge and it was pegged/hot. Checked the engine and temp seemed normal to the touch. Called a tech friend and explained the symptoms. We concluded it was either a faulty sender or gauge. Decided to motor on and deal with it after our family cruise.

The next day we motored away from our anchorage, gauge was normal/cold. Engine warmed up and the gauge reached its normal operating temperature. It has been normal ever since. A fluke, gremlin, bugs, et al. Not sure, but as long as it works, no plan to fix it.

 

[Dan_Y]

Another Similar Situation
Our Yanmar 3YM30 panel overtemp buzzer started to sound, but was some what intermittent. It occurred as we were backing down the fairway into our slip against a strong current. Determined it was a little bit of salt water dripping from the PSS shaft seal vent tube onto the temp sensor...conductive enough to "ground" the sensing wire. The factory temp sensor is just a switch that closes and grounds the sensor wire when above a set temp. Washed off saltwater and it was fine. PSS can sometimes push water up the vent tube when revving it hard in reverse. Added the overflow bottle to the PSS vent tube per Mainsail's suggestion. All fixed.