We've owned this spa for about 7 months. It came with our new house, but is about 7-8 years old. It's a hot springs sovereign model 1. When my wife changed the water tuesday, it decided it was going to have some problems. When we first plugged it back in, the GFCI immediately tripped (and would do so as soon as reset). After some troubleshooting, we realized that we could get it to not trip, if the "Hi Link" cable as unplugged. I think this is the hi temp alarm for the heater...however, the gets will not circulate with this unplugged either. So, does anyone have any ideas what we need to replace? Pump and Heater, Heater only? Whole control system (black box in photos)? Any troubleshooting techniques to help isolate which part(s)? Any good / cheap part suppliers? If you need any additional info please let me know. I would really appreciate any help! Here is a link to some photos of the guts:

http://hankmetzgerlandscape.com/_testing/hottub/Last_Import.html

Most likely the heater.

When you unplug one of the thermistors it sends a message for the heater to not come on, and if no power is getting to the heater it will not leak current to ground and trip the breaker.

That was my guess as well. Any thoughts as to why the pump will not run (at least not on jet mode) with out the heater? According to local support, they are separate...but I don't trust their opinions much. Also, can you suggest an online reliable parts supplier? Thanks!

The jets will not run if one of the thermistors is unplugged and the power light is flashing.

Ok, I will purchase a replacement tomorrow - either online or from my dealer. Can anyone point me to a technical service manual of some kind that will walk me through the replacement? Thanks!