Pentair mastertemp troubleshooting

[Jesse H]

I'm a part of an hvac company who dabbles in a little bit of pool heaters. we have a hotel's master temple heater not working properly and no one can seem to figure out what the problem is. the unit tries to Ignite. The ignitor gets power and glows. The blower comes on For about 10 seconds but no power to the gas valve. No error codes are anything and at'll. Does this cycle over and over again without stopping. We have replaced or checked all sensors, Ignition board, control board, igniter, gas valve. Any ideas?

 

[1poolman1]

Does the blower shut off after the 10 seconds? Check the air-flow switch tubing. Check the wiring to it as well. Have seen the nipples on the blower orifice with cracks that will cause this as well.

 

[ajw22]

Could be a bad Fenwal box.

Let’s see if @swamprat69 is ariund.

 

[swamprat69]

Ignitor warm up is 20 sec.. Trial for ignition is 7 sec. and that is when the gas valve should be powered on. This should be the manual for the heater https://images.inyopools.com/cloud/documents/pentair-heater-mastertemp.pdf The connection and ladder diagrams should be on pages 36 & 37. During the firing sequence do you have 24V between "GND" and "VAL" on the Fenwal after the ignitor warm up and during the 7 sec. trial for ignition. If so, you should show 24V at the 2 connections to the gas valve unless the AGS switch is open or the 24V common ( GND) to the gas valve is open.

 

[generessler]

As has been hinted, the Fenwal ignition control has its own led, which flashes codes when it sees something wrong. This isn't documented in the manual afaik. There's a legend for the codes on a label on the device itself. Another resource is here.