I just recently purchased a used Hot Spring Sovereign hot tub. It is an older model believe an '89. Has only 6 jets and the control panel has two dials (one for heat and one for light) and a push on / off jets button and runs on a 110v(?).

I have set the tub up and it is heating, however it does not seem to get very warm and also tends to cool down if jets are run for awhile. The floaty thermostat I bought registers between 90-94, but the water doesnt feel that warm to the touch.

The heater dial has a lot of marks then goes from 1-9. I dont have an owners manual so dont know which is high and which is low.

From my reading I understand that more than likely the heater only heats when the jets are off is this right? Is there something I should check or change to make it get warmer? Winter is coming and at this point Im thinking this hot tub is only a good 'summer' tub.

Appreciate any help you may be able to provide. I am definitely a newbie!

Well first of all, a 110 volt tub is only going to heat satisfactory if it has a proper fitting cover. To test if the heater is working you will need an AMP meter, you can do a check and make sure it is getting voltage. The tub is going to tens to loose heat as the jets are running, that is correct, and in a 110 set up the heat will not run when the main pump is on, it would draw too many amps.
As for the T-stat, crank it up! 9 is going to be the highest.

Thanks for the quick response. I think Im going to have to call a service tech. I have been playing w/the dial and for some reason the temp has dropped to 82. I did add more water this morning so maybe that was it. Have turned it up to 9 and am going to sit tight to see if it heats back up.

thanks again ~ now that I have the set up for a hot tub Im thinking Im going to upgrade soon