Mastertemp 400 AFS error no power to blower

[MLCarlson]

So, I guess I need ICM right? My AFS continuity is zero.
Hard to believe I needed new blower motor, new control board and membrane pad and a ICM all at once. I suspect my original problem was bad motor and needed a membrane pad and a ICM. I can’t imagine what went wrong to kill the motor?? We did have hurricane and pool sand filter tank crack open after these two, the spa heater gave service light and AFS light and a pool spa tech found bad motor.

 

[JamesW]

If you're getting 24 VAC on the wire unplugged from the IND terminal on the ICM but the voltage drops out when you plug it onto the ICM, that would seem to indicated that the ICM is maybe shorting to ground.

 

[JamesW]

Maybe a power surge?

What is the supply voltage to the heater?

 

[JamesW]

Turn off power and unplug the wire from the IND terminal of the ICM and check for continuity from the IND terminal to ground to confirm a short.

 

[MLCarlson]

I


Yes, I get 24 volt on wire unplugged from ICM

Maybe a power surge?

What is the supply voltage to the heater?

I have the red 12 position plug with label 240 so I assume 240 but not sure from CB box.

 

[MLCarlson]

Turn off power and unplug the wire from the IND terminal of the ICM and check for continuity from the IND terminal to ground to confirm a short.

Ok will do, if zero or short what does that mean?

 

[MLCarlson]

Turn off power and unplug the wire from the IND terminal of the ICM and check for continuity from the IND terminal to ground to confirm a short.

I get a reading from 3.8 to 48

 

[MLCarlson]

Ok will do, if zero or short what does that mean?

I get a reading from 3.8 to 48

 

[MLCarlson]

I thought heater was 120 but that black recepticle is not plugged in the red 240 is.

 

[JamesW]

I get a reading from 3.8 to 48

It would indicate that the there is an internal short in the ICM going to ground.

 

[JamesW]

Inside the ICM there is a relay with a coil voltage of 24 VAC.

The 24 VAC closes the relay to send power to the Inducer/Blower.

I don't think that the relay uses the ground as the other side of the relay, but I am not sure.

If it does, you will read the resistance of the relay coil by measuring from the IND terminal to ground.

So, maybe there should be a reading, I will try to find out.

The dropout of the 24 VAC when you plug in the wire would seem to indicate a bad ICM.

Maybe there is a partial short.

Is the resistance reading fluctuating?

 

[MLCarlson]

Thanks for your help. This may sound crazy but what would I see going on if the Pool spa tech who came out in the beginning, unplugged the 12 position 120 recepticle to do testing and plugged in the 240 instead? I don’t have original pictures before that service call.

 

[JamesW]

I thought heater was 120 but that black receptacle is not plugged in the red 240 is.

Sometimes people use the wrong plug and this can cause problems and damage the heater.

Since the heater has been working, I don't think that the plug could be the wrong one.

Is the breaker a single pole or double pole?

I'm not sure why the tech would have switched the plugs unless they thought that it was wrong from the start.

Check the supply voltage to confirm it is correct.

 

[MLCarlson]

Inside the ICM there is a relay with a coil voltage of 24 VAC.

The 24 VAC closes the relay to send power to the Inducer/Blower.

I don't think that the relay uses the ground as the other side of the relay, but I am not sure.

If it does, you will read the resistance of the relay coil by measuring from the IND terminal to ground.

So, maybe there should be a reading, I will try to find out.

The dropout of the 24 VAC when you plug in the wire would seem to indicate a bad ICM.

Maybe there is a partial short.

Is the resistance reading fluctuating

Yes it fluctuates high and low

 

[MLCarlson]

Sometimes people use the wrong plug and this can cause problems and damage the heater.

Since the heater has been working, I don't think that the plug could be the wrong one.

Is the breaker a single pole or double pole?

I'm not sure why the tech would have switched the plugs unless they thought that it was wrong from the start.

Check the supply voltage to confirm it is correct.

It is a double pole both labeled 20

 

[MLCarlson]

It is a double pole both labeled 20

Ok will check. Getting dark here so I’ll check back in tomorrow after checking CB is 240.

 

[JamesW]

The relay closes F1 to F2.

If the IND wire is getting 24 VAC, the F2 wire should be getting 120 volts to ground.

Remove the F2 wire to see if the F2 terminal is getting 120 volts when the IND wire is sending 24 VAC.

 

[MLCarlson]

Hello gone due to holidays. I replaced the FENWAL ICM and im getting blower motor to come on. This is good improvement. But, I’m still getting the ASF error. I short the AFS switch and I hear a click and heating light comes on but does fire up. Any idea on what’s next? I tested the AFS switch for continuity and it was fine but I’m ordering new one anyway. Thanks

 

[MLCarlson]

Hello gone due to holidays. I replaced the FENWAL ICM and im getting blower motor to come on. This is good improvement. But, I’m still getting the ASF error. I short the AFS switch and I hear a click and heating light comes on but does fire up. Any idea on what’s next? I tested the AFS switch for continuity and it was fine but I’m ordering new one anyway. Thanks

Does not fire up heater chamber.

 

[ajw22]

But, I’m still getting the ASF error. I short the AFS switch and I hear a click and heating light comes on but does fire up. Any idea on what’s next? I tested the AFS switch for continuity and it was fine but I’m ordering new one anyway. Thanks

You cannot short the AFS before the heater starts.

The FENWAL looks for an open AFS before it starts. If it sees a shorted AFS it throws the AFS error and says you have a bad air flow sensor.

The FENWAL wants to see an open AFS before startiong and then see the AFS close after the blower begins operating. If the FENWAL does not see the proper sequence with the AFS it throws the error.