SoBayJim

Here's the background: I have a 2009 Sundance Certa 780, wired for 240V/60A which was purchased used in 2014 from a reputable shop with one year warranty, which is of course now expired. We’ve used it on average five nights a week since professional installation for 20 to 40 minutes per soak (I don’t know if that is considered a little or a lot, but I miss it already). I have no idea how much use it saw with the first owner, but it was in very good visual condition. Symptoms: The water no longer heats up. Heater light illuminates on the panel as expected. Both pumps work as expected. Pump one in both low and high modes, and pump two in high mode. Ozonator continues to blow bubbles when circulation pump is on. The filter is clean and there are no visible obstructions in any transparent lines accessible with the side panel off. Troubleshooting conducted to date: Confirmed the flow switch works via ohm meter. The circuit closes when pump is on and is open when pump is off. A flow error appeared on panel when I removed the J3 connector to test, but has not shown an error at other times. Confirmed the temp sensor is working. It reads about 21K ohms resistance and water temp confirmed via manual thermometer to be low 90’s farenheit. Measured voltage to “heater in” connectors to J7 and J8 at terminal block is 240v. Measured amperage to pumps to confirm inductive amp meter working correctly, but I didn’t get any reading on J7/J8 wires, or J9/J10 leads to heater when heater light came on (and heard relays click). With all power disconnected, I pulled J9/J10 and checked the wires from the heater, which registered an open circuit. No resistance on any setting. My conclusion is that I have a bad heater unit. What do the experts here think and is that reasonable on a seven year old spa? What other trouble shooting steps would you take prior to ordering a non-refundable part? So, if I’m correct and it’s the heater unit, it appears to be a Therm Products Heater C3229-2A for Jacuzzi and Sundance Heater Assembly 6500-402, 6500-403 120/240 Volt. If these conclusions are correct, where the heck can I find installation instructions? I’m comfortable with DIY, but having never worked on a spa before, so would like some info before I commit. For example, is it safe to assume the spa needs to be drained? Then it looks like there are a few wires to connect and a couple of hose connections. What else am I missing? Thanks in advance for the help.