Another Mastertemp 400 question ....

[TX-Pool]

Ok, I forged on with this perplexing puzzle.

As mentioned, when Spa ON, the led display was reading way high water temps, 102, 107, 105, etc. Current actual water temp is around 81.


I traced info to a misreading thermister as most likely culprit.
Old one on the left, looks like corrosion.


After thermister replacement, and Spa ON, the water temperature reading was correct.
However, I now saw that Service Heater was on, the back of the board showed AFS error.


I had decided to get an inexpensive aftermarket PCB along with the thermister - my thinking was that I wasn't going to buy a $500 PCB just to see if it made a difference. I installed the replacement PCB only as a verification and it also showed the same water temp, Service Heater light and AFS led on the back.

This was telling me that maybe the water temp reading (thermister) was an additional problem that was unknown at the beginning.
With the water temp reading resolved, I took a look at the AFS issue.

I know that the AFS itself is functional from earlier testing. What it's telling me in this case is the obvious - the air blower isn't coming on, therefore no airflow, therefore the AFS isn't closing.

So now the troubleshooting is somewhat more focused on what the blower motor needs to turn on.

I went back through the wiring diagram, looking at the motor circuit, which is set up for 240v.

I always verify that the actual wiring color/tag matches the wiring diagram.


I don't see a start capacitor in the diagram, so I'm thinking that this system doesn't have one.
That would be a simple check for a no-start.

I also am checking wiring continuity through the various connectors.

Something curious when I checked the Fenwal F1 and F2 terminals ...
- F1 is constant 120v as expected.
- I was wrong yesterday about the F2 terminal - with Spa OFF, if I unplug the motor harness plug, I get 0v at the F2, but with the motor plugged in (still Spa OFF), F2 sees a constant 120v. This to me seems wrong as F1-F2 should be a relay activated by Spa ON command.
- There is no audible click of any sort at the Fenwal (F1/F2 relay) when Spa ON.
- The red diag led on the Fenwal is never lit or flashing.
- I also want to re-verify why no 24v at the IND terminal at the Fenwal, with either the old or the new PCB.

Next steps:
- I'll finish going through the unit wiring to be sure connectors are ok, etc. There's no visibly damaged wiring anywhere.
- I believe that if I (turn off power first) connect the F1/F2 wiring directly, the blower motor should run.
- I see some additional means of testing the motor operation via alternate wire connections, but right now I'm not completely familiar with that.
- If the blower motor runs then indeed the Fenwal may be at fault.

Right now I'm trying to understand the 6 wires going to the motor, which appears to be wired for 240v. I could see 2 hot and a neutral but I really don't yet get the other 3 wires. I'm trying to find a motor schematic to understand better,
especially before trying to test operation.
Edit, I found this that I think can help guide me....

Unexplained voltage Reading from Mastertemp 400 Blower Motor

I suspect I have a bad motor, but wanted to check here before replacing it. I'm getting a voltage reading Pentair tech support could not explain when I talked to them by phone. My heater will not start. After the failed starts the following are on: Service Heater, AFS LED, and the ICM LED...

www.troublefreepool.com

 

[TX-Pool]

Spa OFF, I jumped F1 and F2 directly after disconnecting them from the Fenwal.
Blower started immediately, no issues, ran fine.

- I think that the motor itself is ok.
- All power leads to the motor are intact.
- I have 2 PCBs that are yielding the same result of Service Heater (AFS), and I've verified that the blower is functional
- No other codes or warning less on the back of the board

- I'm leaning towards a control issue, maybe the Fenwal, so I'll look at those checks.
- I need to recheck that the F1-F2 relay is indeed closing when Spa ON.
- Also re-check for the various 24v readings as outlined before. The heart of this is the 24v transformer, as mentioned I've gotten readings of 27v which I think is ok, indicating functioning transformer.

 

[ajw22]

Replace the Fenwal module.

 

[TX-Pool]

I agree, I'm still going to go thru the 24v checks. I also want to see if any sort of led activation on the Fenwal, but I'm going to order another one.
Thanks.

Edit
- Spa OFF , F1 AND F2 have 120v, this seems to indicate an issue with the relay, as F2 should have 0v when Spa OFF.
- SPA ON, F1/F2 remain each at 120v, IND to ground 27v.
- Spa ON, same Service Heater/AFS lights
- per wiring diagram, at PCB, J7-1 and J7-2 are shown as 24v, connecting directly to both transformer leads. Only J7-2 has power, 0v at J7-1. Shouldn't there be 24v at both?

So the fenwal has essentially 24v at IND, F1/F2 120v but no blower start..
Direct connect F1/F2 with Spa OFF, blower runs fine.
No red led alarm from fenwal.

The final no-blower logic still escapes me other than wondering about both fenwal and transformer......however, the PCB powers up no problem, so I'll revert to recommendation pointing to fenwall.

 

[swamprat69]

Is your heater supply voltage 240V? How are you measuring voltage at the F1 and F2 contacts on the Fenwal? Hopefully not individually to ground! If so, F1 will read 120V to ground as 1 leg of the supply to the motor and F2 will read 120V to ground as the second leg of the motor supply voltage "through the motor windings"! If the motor runs at 240V, the only way to check the F1/F2 Fenwal contacts "using voltage" is to check the voltage from F1 to F2 directly. It should read 240V when the relay is not pulled in and 0V when the relay is pulled in. Another way to check the relay contacts would be to pull off the wires at F1 and F2 and check continuity between F1 and F2. It should read infinite ohms with the relay not pulled in and 0 to very low ohms with the relay pulled in.

 

[TX-Pool]

Is your heater supply voltage 240V? How are you measuring voltage at the F1 and F2 contacts on the Fenwal? Hopefully not individually to ground! If so, F1 will read 120V to ground as 1 leg of the supply to the motor and F2 will read 120V to ground as the second leg of the motor supply voltage "through the motor windings"! If the motor runs at 240V, the only way to check the F1/F2 Fenwal contacts "using voltage" is to check the voltage from F1 to F2 directly. It should read 240V when the relay is not pulled in and 0V when the relay is pulled in. Another way to check the relay contacts would be to pull off the wires at F1 and F2 and check continuity between F1 and F2. It should read infinite ohms with the relay not pulled in and 0 to very low ohms with the relay pulled in.

Dang, yes I measured each side (F1/F2) individually to ground! And yes they each showed 120v.
I'm not home till Sunday but I'll check exactly as you described.

Many thanks to you and ajw for your help, this has gotten me twisted up a bit trying to sort.

 

[TX-Pool]

Update....

I was so curious about this, I decided to take another shot at the relay F1/F2 before I headed out.

Spa OFF - no continuity
Spa ON - NO continuity.

That's it, failed Fenwal as you both have described. Very simple relay check.

Very much appreciated, thanks.