I have just aquired an old tub don't know the name pieced it together from a couple different tubs and it all worked,until I realized I didn't have a filter so I installed one and now the heater doesn't come on at all! I'm positive it has nothing to do with my filter installation, but here are my symptoms (catalina controls rc7) my deck control is very small with 4 little buttonsand a heat knob and two indicator lights one is for sys and the other is for heat. the heat light no longer comes on and when I checked the voltage at the heat element I have nothing, when I depress the relay springy thingy I get 220v like I should, so I'm assuming it is some control issue I don't really want a new circuit board but I wish I knew which of those low voltage wires controls the heater so that I could add some other switch or something I don't need the light I would however like heat. please help
Thankyou Dan

Check on your heater assembly for a pressure switch screwed into it. It's possible that the filter installation reduced the pressure getting to the switch, and thereby preventing the heater from turning on. By chance did the water pressure seem to go down at the jets after the filter installation? If so, I would suspect this to be the case. If not, then I'm sorry I sent ya on a wild goose chase