Heater Ignites then shuts down within seconds, won't ignite again.

cmarkantes

Member
Mar 7, 2022
10
Cave Creek, AZ
Surface
Plaster
Pentair Mastertemp 400. When I start the heater, the fan comes on, it ignites, then shuts down and won't re-ignite. We've changed so many parts its almost completely rebuilt. We started with the ignitor because it wouldn't light at all. Now it ignites but doesn't stay lit. We changed the control board, the ignition control module and now don't know which way to go.

Thanks for any help you can offer
 
Pentair Mastertemp 400. When I start the heater, the fan comes on, it ignites, then shuts down and won't re-ignite. We've changed so many parts its almost completely rebuilt. We started with the ignitor because it wouldn't light at all. Now it ignites but doesn't stay lit. We changed the control board, the ignition control module and now don't know which way to go.

Thanks for any help you can offer
Get a piece of wire, preferably green, and follow the instructions on page 3 of this manual. It may help. Pentair knows there is a problem with flame sensing at times and this kit was made for that issue.
 

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Is the LED on the Fenwal module blinking when it shuts down?

Have you checked that the thermal regulator opens at 120F in a pot of water?

What parts have you replaced?

Are the parts genuine Pentair parts?
 
Check the gas pressure static and dynamic.

Check the Flame Current.

Check the Fenwal LED.

How old is the heater?
Do the tests as described before responding with the same post.

We're not going to get anywhere if you are not going to follow the recommended tests and provide the requested information.
its virtually new.
Meaning what exactly?

Is it used?

How old is it?

Did you verify that it worked?

Where did you get it?

MasterTemp 400 heater.
Model Number and Part Number?

Date on sticker?

Natural or Propane?
 
Is the LED on the Fenwal module blinking when it shuts down?

Have you checked that the thermal regulator opens at 120F in a pot of water?

What parts have you replaced?

Are the parts genuine Pentair parts?
There is no blinking lights on Fenwal, we've replaced the the ignitor, control board, thermal regulator, high limit switch. All Pentair parts.
 
Did you test the new thermal regulator to confirm it opens at 120F? Pentair has had some duds.