Best Hot Tubs Deals! Real User Reviews: Pentair 42001-0053S Electrical Systems Thermistor Replacement Pool and Spa Heater

Buy This Item


This thermistor is designed to use with Pentair Sta-Rite Max-E-Therm pool and spa heaters electrical system and also compatible with Pentair MasterTemp pool and spa heaters electrical system. Measures 6-inch length by 6-inch height by 6-inch width.

User reviews

I have a Pentair pool heater that stopped heating, showed scrolling temperatures on the control board and then displayed error code E01. Called pool service. Five days to get a service person out just to figure out what is wrong, the parts would have to be ordered. I looked up the error codes on Google. Said it was a bad thermistor. Ordered part from Amazon Prime. Delivered overnight. Turned off water, closed the valves. It's basically a little plug with two wires that screws into the inlet pipe inside the heater, lower right side. Remove side access panel, two screws. Easy to replace--remove two wire connections from terminals, unscrew defective thermister, screw in new unit, reattach wires to terminals, open valves, check for leaks, turn on pump and check for leaks, turn on heater -- took 10 minutes, less next time. Needed 7/8" wrench. I happened to have a deep socket. Was careful not to over tighten. Works like new.
Very easy to replace. Remove cover with four 5/16 hex screws, slide each half off. One screw holds the cover over the thermistor. We used a crescent wrench to remove. Voila, all fixed! Note it did not solve our problem of the unit not starting up, although the E01 error code did not show after replacing. We gather it was also bad, although the old Thermistor did have the correct kohm reading as far as we know. After further examination, we have the AFS Led light lit on the board. Now we will replace the AFS.
Fixed the problem! My Pentair Mastertemp 400 heater was reading 10 degrees higher than actual so would not heat the spa past 94. Turns out thermistors in salt water pools only last about 3 years, so this part is pretty much a consumable to have on-hand. For those of you replacing this on your own, it's located behind the side panel in the upper left corner of the water pipe input (several other sensors look almost identical from the outside, so it took me a couple tries to find it).
Repaired my heater after it was malfunctioning because of a faulty temperature readout. Cost about 70% less than my local pool store
It is easy to replace this unit, but use caution when you install it. I torqued it down too far and cracked the water manifold. The manifold is plastic rather than the metal it appears to be. I needed to replace the water manifold and that is a larger task and additional cost.
Replaced a couple things for the pool/spa heater and decided to do a tune up!So easy to replace, becareful tho don't over tighten!
Bought to address problem with heater reading about 20 degrees hotter than the water possibly could be. Was a little concerned that the failure mode was listed as either "short" or "open" in the instructions. However, replacing it solved the problem. Installation was easy, need a large monkey wrench or a deep 13/16" socket wrench.Disappointed in the "1-2 extra processing days" on something supposedly in stock and sold by Amazon. Did delay repair until after the holiday. It clearly wasn't for adding protection. Packaging was minimal and rough handling could have easily damaged the terminals.

View all reviews

We will be happy to hear your thoughts

Leave a reply

%d bloggers like this: