I have an old Barett Aqualine hot tub. When the temp drops the circuit that brings in the heater chatters sometimes untill the gfi kicks. If I turn the control passed the bearly on point it pulls in fine. Is this a thermostat problem?

It could be the thermostat or the relay. Take the thermostat line off the relay coil and check the voltage when it calls for heat, or the continuity depending on how it's set up. See if it fluctuates on the meter or if it is steady and has a clear on/off. If not, replace the thermostat. If so, go with the relay.

Depending on how long this has been going on it may be a good idea to go ahead and replace the relay anyway.

I guess I should have noted that I had recently replaced the relay. The hot tub is an old one we got from my mother used. The issue that made me replace the relay was a heating one also. When the temp would drop nad the thermostat tried to bring the relay in it just clicked once but the heater didn't come in. Upon inspection the contacts were cooked. After a few weeks of normal operation we have this new situation. After your post I'm now leaning toward replacing the thermostat.

Yeah, I would go with that. Sounds like the thermostat was probably the culprit in the death of the previous relay.

Thanks a bunch. With this old spa I bet I'll be asking you guys allot of questions.

I'm going to post this on the Conventional Spa/Hot Tub Controller Problems forum also but here's what i found;

My old spa has a td command center series 9000 top side control I'm guessing that I need to replace this. Should any top side air control fit and replace it?

Status up date on the old spa. I got the new topside control and the installation went fine. We have the heat circuit pulling in solid, so I believe that the topside control needed to be replaced but that didn't fix the gfi problem. The spa will run in low speed heat mode for anywhere from 1 to 30 min. It will run the jets, highspeed no heat for hours without tripping. I disconnected the heater and it still kicks out running the pump only in low speed.

Any Ideas?

This may help

http://www.alliedinnovations.com/pdf/W1010a.PDF

The relay that was chattering may need to be replaced. It will still engage even with the heater disconnected, but may not when the pump is on high (is this a 120v tub?). Probably the regulator contactor, maybe the high limit.

Yes its 120v. I'll first try replacing the one I haven't replaced yet.

Thanks again for your help.

I'm experimenting today with the high limit switch and the pressure switch part of the circuit after you let me know that it was still active with the heater disconnected. With both of them unwired the pump ran at low speed for a full hour but the heater was not on. I next jumpered the high limit switch, the heater pulled in but the gfi failed within the first 15 min. Next step I jumpered the whole circuit and hard wired between the high limit and regulating contactors. The spa is still running after 2 hours with the temperature climbing normally. I'm leaning toward the pressure switch as the culprit. What is the function of this switch?

I did a little searching and I know now what the switch does. I'll find suitable replacements for both the pressure and high temp switch.