I have a Caldera Aventine hot tub. 5 years old, regularly maintained, no issues, water changed frequently.
After a water change recently the heater kept shutting off. Air lock, right? Here's what I did:
1. Ran water hose through filter hole to break lock. Done several times, no success.
2. Cracked every pipe seal to bleed out air - no luck.
3. Drained tub entirely and refilled slowly through filter hole - no luck.
4. Forced air through pipes to try and force out air lock - no luck.
5. Forced water through pipes to break lock - no luck.
6. Blood offering to the spa gods - didn't help either.
I can't imagine at this point that it's an air lock. Runs OK on high speed with no shutoff. At low speeds it heats the water, but shuts off anywhere from 10 seconds to 10 minutes of operation. At that point there is a click from the circuit board; a half-second later the GFCI clicks and everything shuts off.
Failing heater? Faulty circuit board? Or failing GFCI?
Any and all help is greatly appreciated.