Master Temp 200 randomly says service needed

[McAlsop]

Hoping someone has seen this issue before. We have our pump doing 2 cycles/day. Our Master Temp 200 heater has always turned off and on fine along with the pump for a few years now. Within the last couple months it will randomly not automatically start with the pump and will have Service Heater lit. If I hit Heater Off, then Pool On, it returns to working just fine until it randomly decides not to turn back on with the pump again and say Service Heater again. Sometimes this can be the next cycle, or it can be weeks like it just did (I thought it fixed itself).
Any ideas???
Thanks!!

 

[Poolbreh]

Is it hooked up to automation?
The minimum flow for 200kbtu is 20 gpm, when was the last time the filter was cleaned?
Is it natural or propane gas?
I would open the front and visually inspect
For any rodent damage.
There isn’t much to go off, probably the best thing to do is next time the service light comes on check the fenwal for any flashing lights, and check behind the board to see if any sensor LEDs are lit.
The fact it’s so infrequent will probably make the diagnosis a long one.

 

[ajw22]

You are probably getting ignition failures. When you have the Service Heater LED on you need to check the diagnostic LEDs on the back of the board or on the Fenwal box.

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com

 

[McAlsop]

We have no automation. I actually did open it up and thought I might find some damage because there was a chipmunk in there last year. But it was still clean this time. The filter is due for a cleaning, but it does start again when I turn it off and on, so I didn't think it was a flow issue. Also it's hooked up to natural gas.

I was hoping this happened frequently and I could just try replacing something that worked for someone else. But since it isn't I'll read through what you provided and familiarize myself with these diagnostic LEDs and/or Fenwal box.

I will post back here if I have another question or figure it out. Thanks!