Max e therm low temp

[bubbles^2]

After evicting mickey and minnie from our max e therm, I had to resolder the wires to the high limit switch and the thermister and a yellow wire off the control board. After this I put some chicken wire up on the upper vents, and then stuffed a bunch of steel wool into the front and rear openings.

The heater fires up fine, but the temperature on the display shows at 62 degrees, I've had it set to 98 degrees, but since the temperature never changes it heats way past 98 degrees.

Oddly from everything I can find it appears that if the thermister fails it fails high, ie the temperature it reports is 127 degrees. I seem to have the opposite issue.

Once I get some weather that doesn't include rain I'll have to open the casing up again and see if mickey and minnie have moved back in, or if the wires going to the thermister may have been more damaged than I had previous thought.

Anyone else have any suggestions on things I may have missed, or similar issues?

 

[bubbles^2]

Alright, some more work.

I replaced the ignitor because the rodents chewed up the wiring to it.

During this I started the heater and it fired up normally. Temperature still stays at 60, sometimes dropping to 59. After 20 minutes, the SWG was reporting 88 degrees, but the heater still hanging out at 60 degrees.

I went ahead and unhooked the thermocouple and connected the new one. No change in temperature. Then to test if it really made a difference I unhooked the new thermocouple and left the harness unconnected. Heater again fired up with no error code.

Based on this I think I either have some short on the wiring, or perhaps worse yet I have an issue with the motherboard. Which won't be fun as I have a earlier model so I'll need to replace the motherboard and the display.

I'm going to check the wiring from the thermocouple to the motherboard with a multimeter to try to see if there is a internal short, if there is, remaking the wiring from the mother board to the actual sensor doesn't appear to be that diffiicult.

 

[ajw22]

Connect a 10K resistor in place of the temperature thermistor.

If the heater display reads 76F then the thermistor is bad.

If the heater reads anything else then the board or wiring is bad.

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com

 

[bubbles^2]

The thermister in the heater is reading 14 ohms, the new one is reading ~9 ohms. Wiring has no resistance, ohm readings are the same through the wires at the motherboard.

I need to see if I have a 10k resistor to even test, radioshacks are a bit on the rare side now.

EDIT: well that's hilarious. amusingly I actually have two packs of 10k ohm resistors from when I did a motor/speedo swap from 10+ years ago.

 

[bubbles^2]

with the 10k ohm resistor the temperature still reads 60 degrees, kinda expected at this point as even with no sensor it reads 60 degrees.

So likely the board is gone. Interesting problem, the heater does still work, it just doesn't stop as the temperature doesn't change. I'm almost tempted to try to reflow the solder on the board and see if that'd make a difference. But in this case I could make things worse as the heater does still fire.

 

[ajw22]

Likely rodent urine destroyed the board.