MiniMax NT LN Heater Igniter Voltage of 79 VAC

[GregoryLR]

Hello Forum,
[FONT=wf_segoe-ui_normal, Segoe UI, Segoe WP, Tahoma, Arial, sans-serif]I have the MiniMax NT LN series Pentair heater. I originally had an E04 error with the only symptom being that the gas did not ignite. The blower seems to be working properly so the E04 error did not make sense. The gas valve also seems to be working properly. On researching, there were recommendations to replace the igniter. Since the heater is about 10 years old, I went ahead and replaced the igniter. The heater still does not ignite. I tested resistance and the igniter is about 50 ohms. I tested voltage supplied to the igniter and voltage is about 29 VAC prior to the igniter warming cycle and then about 79 VAC during the warming cycle. The igniter does not warm up to the point of glowing. It actually doesn't seem to warm up at all although I am not going to touch it to confirm this. Shouldn't the voltage to the igniter be 120 VAC? Does this indicate that the Fenwal Ignition Control Module is the issue? Thank you all for your help![/FONT]

 

[kadavis]

Are you using a True RMS meter, otherwise you will get false readings at igniter

 

[ps0303]

If you can not see the ignitor glowing red, then it is either not getting the proper voltage, it is bad or the ignition control module is bad. The ignitor on this unit should be a 120V ignitor, not 24 volts.

Here is the manual for this unit. https://www.parts4heating.com/v/vspfiles/images/pdfs/MiniMaxNTLowNOx.pdf

 

[GregoryLR]

I am using a True RMS Multimeter from Extech.

 

[GregoryLR]

Thank you for your reply. This is the process of elimination that requires buying parts that are the mostly likely next suspect. Since the igniter is showing 50 ohms of resistance, does that mean that the igniter is likely good, which leaves the ignition control module as the likely bad part? I am confused why I would see some AC voltage (29 VAC) before the start of the igniter heating cycle. Seems like it should go from 0 to 120 and then back to 0.

 

[ps0303]

If the control module is bad it could be showing you that. Did you disconnect the ignitor and hook your meter leads into the wiring and then let the heater run?

 

[GregoryLR]

To test for voltage, I first disconnected the two wires that connect the igniter. I inserted the mulitmeter leads into the wire connectors connected to the control modules and selected the AC voltage measurement on the multimeter. I then ran the heater through the full cycle several times. The blower runs as normal, the igniter heatup cycle begins (except voltage doesn't reach 120), the gas valve opens, the igniter voltage is cut when the gas fails to ignite, and the gas valve closes. The blower continues running for the purge cycle. I can smell gas in the purge so I know that the gas valve is opening and closing. To make sure that the multimeter is working, I inserted the leads into a standard outlet and the meter showed 120 VAC. Am I testing for voltage from the control units correctly?

 

[ps0303]

Yes sounds like a bad control module.