Not getting power to Mastertemp400

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JumpingGecko

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Feb 28, 2025
9
Austin, Tx
The control panel on my Pentair Mastertemp400 heater has stopped getting power. I’ve read other post trying to fix this myself, but I’m at a point where I don’t know what to check next. Any guidance would be much appreciated.

My system is about 15 years old and it’s a Pentair Easytouch control panel connected to a Mastertemp400 heater. We use the heater several times a week and it has been working fine for the last couple of years. I know that I have to have the spa on for the heater to get power. When I press the ‘spa’ button I no longer see “HEATER” displayed on my easy touch control panel and no lights light up on the heaters control panel.

Here is what I’ve done so far:

I checked the voltages on the heater and I’m getting 220VAC input and 28VAC out of the transformer. I checked the plugs to the control board and the 4-pin connector at J7 has 28VAC and the 5-pin connector at J1 has 0VAC (brd_vac.jpg attached). At this point I thought the control board was bad so I replaced it. The issue remained. Still no power. Next, I checked the wire between the easytouch control panel (J19) and the heaters firemans switch. I used a multimeter with audible continuity and verified that each screw post on J19 had continuity to the firemans switch post and they were not shorted together (fsw.jpg attached). What do I check next? I’m out of ideas.

Thanks,
-Mike
 

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JumpingGecko said:
The control panel on my Pentair Mastertemp400 heater has stopped getting power. I’ve read other post trying to fix this myself, but I’m at a point where I don’t know what to check next. Any guidance would be much appreciated.

My system is about 15 years old and it’s a Pentair Easytouch control panel connected to a Mastertemp400 heater. We use the heater several times a week and it has been working fine for the last couple of years. I know that I have to have the spa on for the heater to get power. When I press the ‘spa’ button I no longer see “HEATER” displayed on my easy touch control panel and no lights light up on the heaters control panel.

Here is what I’ve done so far:

I checked the voltages on the heater and I’m getting 220VAC input and 28VAC out of the transformer. I checked the plugs to the control board and the 4-pin connector at J7 has 28VAC and the 5-pin connector at J1 has 0VAC (brd_vac.jpg attached). At this point I thought the control board was bad so I replaced it. The issue remained. Still no power. Next, I checked the wire between the easytouch control panel (J19) and the heaters firemans switch. I used a multimeter with audible continuity and verified that each screw post on J19 had continuity to the firemans switch post and they were not shorted together (fsw.jpg attached). What do I check next? I’m out of ideas.

Thanks,
-Mike
Click to expand...
I forgot to mention the fuse by the firemans switch is not blown.
Thanks,
Mike
 
Jump the Firemans Switch connection in the heater. Does the heater control panel light up when you press POOL ON? If so, the problem is in your EasyTouch. If not, the problem is in the heater.

Report what happens.

Did you replace the MasterTemp PCB with a genuine Pentair board? Show us pictures of both sides of the replacement board.

You still have your old PCB?

What is the water temperature displayed on the EasyTouch screen? Show us a picture of the screen when you turn on your Spa.
 
You are getting 24 VAC at J7 from the Transformer.

The two right pins on J1 provide 24 VAC to the Fenwal Ignition Control Module.

Unplug the connector and check the voltage again.

Unplug this yellow wire and check for 24 VAC to ground.

1740850743979.png

1740850021767.png
 
The Transformer is connected to pins 4 and 3.

Pin 3 is connected to pin 2.

Pin 2 goes to the Fireman's Switch Loop and returns on pin 1.

Test for voltage from Pin 1 to Pin 4. You should get 24 VAC if the Fireman's Loop is closed.

When you get 24 VAC from Pin 1 to Pin 4, the Heater should Boot-Up.

Normal boot-up is 888, 128, and then rX, where X is the software revision number.

Test for voltage from Pin 3 to 2, Pin 3 to Pin 1 and from Pin 2 to 1.

If Pin 3 is connected to Pin 2, you should get 0 volts from Pin 3 to Pin 2.

If the Fireman's Loop is closed, you should get 0 volts from Pin 3 to Pin1 and from Pin 2 to Pin 1.


1740853374778.png
 
That is all fine but first isolate your problem to the MasterTemp or EasyTouch by disconnecting the heater Fireman’s Switch as described in post #3.
 
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ajw22 said:
Jump the Firemans Switch connection in the heater. Does the heater control panel light up when you press POOL ON? If so, the problem is in your EasyTouch. If not, the problem is in the heater.

Report what happens.

Did you replace the MasterTemp PCB with a genuine Pentair board? Show us pictures of both sides of the replacement board.

You still have your old PCB?

What is the water temperature displayed on the EasyTouch screen? Show us a picture of the screen when you turn on your Spa.
Click to expand...
I jumped the firemans switch by removing the 2 wires on the easy touch control panel (J19) and twisting them together (twist.jpg attached). After power, the heater worked fine. Once the pump started I pressed the 'Pool On' and it started heating. I did not expect that. I powered everything off, stripped and reattached the wires to the control panel J19 then powered everything back on. Once powered, I pressed the spa button on my control panel and still no heater. I took a screen shot of the control panel (spa.jpg attached). Water temp 68, set temp 102. What should I check next?

Thanks,
Mike
 

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The problem is the J19 on the EasyTouch.

Either it is not being commanded to close or it is not closing due to a bad part on the EasyTouch board.

Check for continuity from pin to pin on J19 when the heater is commanded on (Call for Heat).
 

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JamesW said:
The problem is the J19 on the EasyTouch.

Either it is not being commanded to close or it is not closing due to a bad part on the EasyTouch board.

Check for continuity from pin to pin on J19 when the heater is commanded on (Call for Heat).
Click to expand...
I checked continuity between the pins on J19 by measuring the resistance across the two screws used to secure the wires. It was 24 Mega Ohm when the spa was on. The same when the spa was off.
 
ajw22 said:
I suspect you have a blown relay driver chip. Read Pentair Automation Systems - Further Reading

Are all of your high voltage relays and actuators working properly?

Check if J19 is closing using your multimeter as described in post #10.
Click to expand...
I checked and J19 is not closing. All other relays seem to be working fine, water feature, cleaner, jets all turn on/off fine.

Thanks,
Mike
 
JumpingGecko said:
I checked continuity between the pins on J19 by measuring the resistance across the two screws used to secure the wires. It was 24 Mega Ohm when the spa was on. The same when the spa was off.
Click to expand...
The relay is not closing.

Resistance should be close to 0 when the relay is closed for heat.
 
JumpingGecko said:
I checked and J19 is not closing. All other relays seem to be working fine, water feature, cleaner, jets all turn on/off fine.

Thanks,
Mike
Click to expand...
Replace the relay driver chips and see if it fixes the problem. The chips are inexpensive.

Otherwise the relay itself is bad and needs to be replaced. @ogdento has repaired EasyTouch boards.
 
The transformer is 24 VAC.

The line going to J7 Pin 3 is considered to be Hot and J7 Pin 4 is considered to be Ground.

Pin 3 on J7 should be connected to Pin2 on J7 and to Pin 1 on J1.

Pin 1 on J1 sends 24 Vac to the Fenwal Ignition Control Module.

Pin 2 On J1 goes to the Ground on the Fenwal Ignition Control Module.

Yellow is Hot and Yellow/White is Ground.

1740865712504.png

1740864249978.png

1740863816449.png
 

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