Going to buy a new Quad Castile thermocouple.

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Minister of Fire
Hearth Supporter
Oct 1, 2008
Western Maine
Last heating season my Quad Castile would more often than not shut down before it completed its startup cycle. I could get it to go most times by setting the stove on high then lowering it to medium once it started and it will run fine thereafter. My gaskets are all good, exhaust pipe clean etc.
Today I tested the thermocouple with a multimeter and a portable propane torch. According to my service manual to go green (on the control box)) the system needs to see ~2.5mV, and to go the final Red ~12mV. The best I could get was ~4 mV. So I'm biting the bullet and ordering an OEM thermocouple. I'm begrudgingly doing so because I'm sure Quad is going to ask a hefty price, but I'm tired of coming downstairs in the AM and the stove cold.

We like coming down stairs on a cold winter morning and seeing the stove running. We really miss that! I wondered if a thermocouple output might diminish with long term use (mine is approximately 15 years old), but could never find any posts regardless of how much I searched.
sometime things need to be changed "JUST BECAUSE" ive never seen a TC go weaker but i suppose its possible. it could have a micro crack in the weld who knows. but it dose sound like your TC is the problem child. Let us know how you make out :)
Will do Ssyko! Heating season almost here.
Ok finally had the time to install the new thermocouple.
First the price wasn't as high as I expected although I still think they want too much.
My cost was $92, it was from the dealer and looked like an OEM part with all the labeling.

I remember reading another post where the poster had apparently cut into the wire sheathing and the wire(s) and shorted something out. I paid particular attention to how I installed thermocouple. Be mindful that the woven steel shield can cut you. Go slow!

For those that might want to change theirs:
Power off of course.
The thermocouple wire is much stiffer than I imagined.
Start by removing the side cover, and disconnecting the two pull apart connections.
Slide open the right-side cleanout door to see better, and pull out the ash pan.
Remove the bolt holding the ceramic cover and bracket then pull the assembly away from the thermocouple.

With the thermocouple exposed push, it down through the hole, it's stiff but it will go.
Underneath the thermocouple takes a 90 Deg. right turn through a hole along with the igniter wires.

This last hole looks like a great place to chafe the new or existing igniter wire so take your time.
Don't try and yank it out or when installing the new one. Bend as you slowly work it through. You can see this hole from the back with a flashlight.

Once out reverse the process.
When you get the themocouple up to the bracket make sure you have enough length so the themocouple reaches the end of the ceramic cover once the bracket is tightened down. You will probably need to fiddle a little.

Now the good news for me. When I tested the new thermocouple, it was much more responsive to the torch and didn't take too long to reach that magic ~12mV level.

Stove started up and completed all steps.
This morning the stove again stared on its own and completed all steps.

I'll keep watching, but so far, I think/hope it's fixed!
Just update since the thermocouple was replaced, the stove has started properly for 2 weeks. Happy camper!