I have a Cal Spa Model # 05-5M-CA-31 that is not heating. The display on the control pad shows the water to be 95 degrees when you first turn it on and then the temperature reading proceeds to rise. This is a false reading because the water is still cold and I know it does not heat that fast. After about 5 or 10 minutes the display will read OH and the motor will no longer run. I have reset the breaker, but the same sequence repeats itself.

First step is to confirm the tub is getting the power it requires. Most tubs are 240 vac, if yours is this type confirm you are supplying 240 and not 120, could have lost a leg from the panel

Yes I am getting power on both legs

So you confirmed 240 reaching the heating element?

We are having the same problem. Did you figure out what to do to fix it? We just purchased this USED hot tub and replaced the heating element. We have read that it could be a dirty filter. We will see!

Almost sounds like It may be Heating but Not flowing. Be sure all valves are open. Its like it keeps heating until OH, which I believe it is overheating.
I would put an Amprobe on the Heater wire.
If you have voltage out of the Control board and it is not heating, The Element is likely open.

Any good Electrician should be able to solve the Problem.
I don't know if Troubleshooting Spa's are in Engineers scope of work, Sounds Expensive, There are Many types of Engineers.
What did the Engineer charge?
Johnterry, do you work for "Family Leisure"(hot tub)?

Hi I have a aqua spa imperial inflatable hot tub when you turn the heat on it works but it not heat up can any one help

It can't work and not heat up, I would clip and Amprobe around the Heater wire to check for draw, can check resistance of element if an Amprobe is not available.
I also say If it has power to the element and it isn't heating, the element is bad.