Mastertemp 400 Service Heater Light on, system not firing

[Turbowilly]

Hi, new to TFP. I have a 4 year old MasterTemp 400 Heater. Currently, I turn the heater on and the Service Heater Light turn-on but the unit does not fire.
I check the wires for mice damage and found none. I also check the OHMs on the Thermistor, Pressure Switch and the Hi Limit Switch.
The Hi Limit Switch did not register any OHMs and there are no error codes on the panel. The water temp is approx. 65-68 degrees.

Could the limit switch be the issue or is there something else that I should be looking for. I called Pentair and they did not have much advise.

Any help would be appreciated.

 

[ajw22]

Welcome to TFP.

If you are getting a "Service Heater" LED, then you will have an error LED on the control board or the Fenwal of the 5 button heaters. Check the diagnostic LEDs or the Fenwal box LED for blinks.

Diagnostic LEDs are on the back of the older 5 button non-connected Pentair MasterTemp heater board. The 6 button RS-485 Connected Heater displays the diagnostics on the heater display or IntelliCenter display.



The following are the LEDs:

1. .....PS (Pressure Switch)
2. .....HLS (High Limit Switch)
3. .....SFS (Stack Flue Sensor)
4. .....AFS (Air Flow Switch)
5. .....AGS (Automatic Gas Shutoff).
6. .....Service System
7. .....Thermistor
8. .....Heating
9. .....Pool On
10. ...Spa On
11. ...Service Heater.

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com

 

[Turbowilly]

Thanks Allen! I'm not sure I'm following. There are no LED messages on the board. It's just the light that is on.

 

[ajw22]

Thanks Allen! I'm not sure I'm following. There are no LED messages on the board. It's just the light that is on.

Have you looked at the LED on the Fenwal?

Does the blower start running?

 

[Turbowilly]

Hey Allen, You are the best. I was able to figure it out. the Fan was clogged from mice debris.

Knock on wood, it's been running for about an hr. Many Thanks