My Onan MDKAV uses 309-0295-01, the part that is in Eric's photo.

   Mark Pitt

  Sabbatical III, SM#419, Rhode Island, USA

On 7/29/2020 10:05 AM, CW Bill Rouse wrote:

WAIT and read this before you order!

Not all Onan Generators in all SMs and 54s are created equally. Use your ohmmeter to check for continuity between the terminals on the temperature sensor on the exhaust elbow. Some Onan models have part 309-0295-01 which is Normally Closed. Other models have part 309-0295 is Normally Open. Which sensor you have depends on your Onan Model and Serial. Check the parts manual for your model to determine how to test this sensor. Or call your Cummins/Onan dealer with your model and serial number.

Good to know: The normal temperature of the exhaust elbow is about 50C and the normal temperature of the coolant is about 80C. Were these in range? How many hours since the last impeller change? Should be less than 300hrs or 12 months. The impeller blades can look OK, but the impeller can be defective. You can have some water flow, but not enough to keep the elbow below about 70C (the approximate cut-off temp).

Also, remember there are a number of sensors in the shutdown system, and these switches will fail. I replaced the exhaust manifold temperature switch and the water-flow switch because of an accumulation of debris inside. I also had one situation with a loose connection on a switch. Did you use your laser temperature gun to measure temperature? 

	CW Bill Rouse Amel Owners Yacht School +1 832-380-4970 | brouse@... Address: 720 Winnie, Galveston Island, Texas 77550  Website: www.AmelOwnersYachtSchool.com

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On Wed, Jul 29, 2020 at 4:02 AM Mark Pitt <mark_pitt@...> wrote:

Eric,

I will order one.  I have never had an issue with mine but you never know.  Thanks for doing this.

Best,

Mark

Sabbatical III, Sm#419, Rhode Island, USA

On Jul 29, 2020, at 1:13 AM, eric freedman <kimberlite@...> wrote:

 Mike,
These are simple thermal switches. They are normally closed.
If the circuit opens up the genset stops.
My problem is sometimes they burn out and other times I hit the switch and it separates.
Fair Winds,
Eric

On July 28, 2020 at 10:41 PM "Mike Longcor (SV Trilogy)" <svtrilogy53@...> wrote:

Thanks Eric. Sent you a message with order details.

When these fail, go bad, or break, how do you know? Does it prevent the genset from starting/running? Or does it allow the genset to overheat if there are issues with the cooling system (broken impeller for example) and potentially damage things?

Cheers,

Mike Longcor

SV Trilogy SM23

Opua, NZ