I have a Leisure Bay 1996 model hot tub (#4000M). THe spa control is a ProShield Ultra. Last week the Hi Limit was tripped and I had to reset it. Now the hot tub will get too hot when I have it set on warm - it wont turn itself off. It also will not cool down when I set it on cool. What could this be. I think it may be the thermostat? I really have no clue what to look for.......any help would be appreciated!!

Thank you.

Could be a problem with your thermostat, but most of the time when you have a constant heating problem, it's usually a stuck contacter (relay) that actually powers up the heater. Sometimes you can tell which is the problem by listening closely to the thermostat. When you start from full off and go to full hot, somewhere inbetween you should hear a faint "click". But that only applies to a mechanical thermostat. If your's is digital, which I suspect it is, I would suspect the heater contactor (relay) is bad.

Thanks for the help. I am planning on replacing the thermostat and hope that will help.... About the relay, how do I buy that part and is it easy to fix or should I hire someone to come out and do it for me?

Replacement of the relay/contactor may or may not be possible, depending on your setup. If you have a digital control on your spa, then most likely the relay is soldered to a circuit board in the control panel and would require replacement of the circuit board. However, if you have a mechanical thermostat, it's likely you have a contactor screwed to the inside of the control cabinet. Follow your wires from your heater element to the box, and the contactor will be the first thing you run into. This item can be found at many electrical supply houses, or even on the internet. Once you find this contactor, a simple rap with the back side of a screw driver might break it free, but this would be only to test to see for sure if it is the problem. It may work after that, but it will fail again, generate heat, and could end up as a bigger problem. So, if it is stuck, replace it.

How do I know if I have a digital control? I havent really gotten to look at all the components of the tub....About how much would a new circuit board cost? Alot, right? I hope it is only the thermostat. Can you tell by looking at the contactor if it has gone bad (i.e. corrosion or something).

Sorry so many questions.....thanks for the help!

If you have a knob that you turn to adjust the temperature, then you have a mechanical control and replacable relay/contactor. (If you can replace the thermostat, it's definentally mechanical) If you have two buttons that you push on a display panel (on the top of the tub), and it shows on an lcd display the temperature, then you have digital. Contactors (relays) will show wear by signs of arcing, or even black carbon around the contacts. Not all relays give up their secrets though, since some are sealed in a black plastic housing and you can't see the contacts. Regarding the circuit board, if you have one, they can be expensive, depending on make and model. Some are as cheap as 300, others are over 1000 (like mine).

Thank you, that was very helpful!
I definitely have a mechanical, not digital tub.
As to the part of replacing the relay.....do you think I could do it or should I get someone to come out? I will replace the thermostat first and if that doesnt fix the problem then it is probably the relay?

Yes, if the thermostat doesn't fix the problem, it is very likely to be the relay. You shouldn't have any trouble replacing this yourself. Typically it is a device with about 6 wires going to it, and 2 screws to hold it to the panel. Just make double sure that you label each wire and make a detailed diagram of where each one goes, before disassembly. If you can, just do one wire at a time.

Good Luck!

Thank you so much for your help!
In your previous message were you talking about fixing the thermostat or the relay?

One other question.......... When I open the door to all the hot tub components there is this big black box that the timer is attached to along with the reset button, voltage "things", etc.... Do I have to remove this "box" to get to the thermostat and all else or do you have to take the wooden sides of the hot tub off (if possible?) I havent seen the rest of the hot tub because of this box. Also....what is this box anyway?

Can you replace the thermostat with water in the tub? (Power to the tub off of course.)

I was talking about replacing the relay. I would really look at that before the thermostat, as it is much more rare that a thermostat will fail first. That big black box you spoke of is your control box. Your relay will be inside that.

Your thermostat is about as straight forward as the relay, in regards to replacement. You do not have to drain the water to do this. There will be a really thin copper wire comming out of the thermostat, and it will go to a tube that goes into the tub somewhere. That wire is attached to a larger copper tube, (or bulb). This is what actually senses the temperature and just simply slides out of the tube. If you do replace the thermostat, make sure that you don't kink the copper wire going to the bulb that goes to the tub. This is a hollow device and uses expanding fluid inside it to tell the thermostat to turn on or off. If that tube gets kinked, the fluid can't flow, and it won't work.

If you can, take a picture of the inside of that control cabinet, and upload it here. If the picture is detailed enough, and depending on the type of relay, I may be able to tell you just from looking at it if the relay is at fault.