Pentair minimax 250 heater shuts off

johnhugo

Active member
Apr 25, 2017
38
Tucson
My Pentair heater fires up (heat comes on) for about 30 seconds and then shuts off. I have replaced the flame sensor and temp probe. The air flow switch is working, but I bypassed it just to be sure. The temperature limit switches are in their normally open position. I can't read the error code on the control panel because some of the led's are out (it has been that way for many years). The error light inside the unit in flashing one time, which (according to the label) is an air flow problem. I think the only air flow sensor in the air flow switch. Any thoughts or ideas? Thanks.
 

johnhugo

Active member
Apr 25, 2017
38
Tucson
I will check that out. It was a couple of weeks ago when I did that. I talked to Pentair and followed what they said at the time. I may have gotten that backwards in my post. Thanks.
Are you sure? Check again. High limits are normally closed.
I checked that out and you are right, they are closed. So that is not it. Any ideas what I can check next?
 

johnhugo

Active member
Apr 25, 2017
38
Tucson
Check the air flow switch. Should close when blower comes to speed. Also check the connections and wiring (all).
I checked the air flow switch and it is working. I looked for any sign of bad wiring (e.g., missing insulation) and did not see any. I pulled off all the connectors and pushed them back on in case there was any corrosion. I added a grounding wire (I read that was a problem with some units). I also verified that the flame sensor is working. There can't be much left! Ideas for the next round? Thanks.
 

swamprat69

Well-known member
Mar 30, 2019
271
Las Vegas, NV
Have you checked that all grounds in the system are clean (bare metal) to the cabinet of the heater, burner assembly and ignition module? It sounds as if you are shutting down on a failure to sense that the flame is there.
 

johnhugo

Active member
Apr 25, 2017
38
Tucson
Have you checked that all grounds in the system are clean (bare metal) to the cabinet of the heater, burner assembly and ignition module? It sounds as if you are shutting down on a failure to sense that the flame is there.
Yes I have. I measured the signal from the flame sensor at the Fenwal and it is receiving the proper signal. I thought the Fenwal may be bad, but everything I have read indicates that it never goes bad. Thanks.