Single pump pool and spa, boost pump, spa jet pump, natural gas heater, Goldline Pro Logic PS-8.
Problem. Running in pool mode, when Heater 1 button is pushed on control panel, indicator light comes on, message changes from Heater 1 Manual Off to Heater 1 Automatic Control and heater runs. Running in spa mode, the message changes but indicator light doesn't come on and heater will not come on.
History. We don't use the heater that much--never to heat the pool (intentionally ) But I'm pretty sure we've heated the spa several times and all worked as it should. Only change I can think of is I changed to Pentair variable speed pump and had to wire the Intellicom II Interface Adapter into the PS-8. Although it didn't seem to be rocket science I suppose I could have messed up wiring somehow. I've checked and double checked but I don't see anything out of place.
Analysis. Hard to do much without schematics or at least block diagram. But...Don't think adding Intellicom Adapter wiring caused this since essentially all it does is parallel the relay inputs to pick up control signals for the variable speed pump motor.
Heater and wiring from PS-8 is OK since it runs on pool mode.
Some signal is missing when in spa mode that lets heater control circuit on pc board know that the spa is running (this is a guess since I don't know the control logic).
Any help or suggestions would be most appreciated.
(Update) Called Goldline tech support and turns out that Spa Heater in Settings menu was on manual off . Changed it to a desired setting and voila--heater now works on spa mode.