Problems started when the heater would shut down when the spa was turned on. It would run up to 86 degrees and shut down. Not happy about the high cost of parts when the repair guys shows up, I punted! I order a 42001-0053S Thermistor and installed it. Now, no power to the heater at all! Chances the new part is bad? Installation step missed? The ignitor was replaced two months ago, $400. The unit inside is clean, no palm rats...