ok we are moving in the right direction !!

Thanks for the heads up on the ground wire as well. I'll have to make sure everything is connected.

Now, on the the fun part..

What is my next step to diagnosing this problem? And where would I find the limit/flow switches to check them?

limit and flow switch should be also in that box... flow switch for sure. It will be screwed right into that square flange of the element if I'm not mistaken. First thing I would do is when you turn on the heat, I would check for voltage at the two large terminals of the element (in that box on the left side). If you have power there, great, now we have to disconnect those same two wires from the element and check the element for resistance across those two terminals. (of course remove power before doing this) The reading should be around 11 ohms. If it is open (infinite) then the element is bad. If you don't have power there, or is less than your line voltage, then we need to do some more checking. Check to see if there are any red buttons (about a 1/4" in diameter) in there. Press it and see if it clicks. This would be the high limit switch. Checking the pressure/flow switch, I would turn on the system, ensure water is flowing, and literally short the two wires going to the switch together, and recheck for power as above. The only thing the pressure switch does is makes sure that water is flowing to turn on the heater.

Hi mchad21,
Did you find the high limit yet?

ok I did some checking and here is was I found:

Line voltage at the receptacle was 121 V.

Voltage at the terminals of the element, when the heater was on, was, I'm pretty sure, zero.

I say 'pretty sure' because the leads on my fluke sometimes crap out, and you have to get it just perfect to get a reading. The area is VERY tight, but I did the terminal and the wires coming off if it with a neon tester and..nothing. I'm going to borrow a Wiggie from my brother tomorrow and verify for sure.

I did not measure resistance, and I did not see any button anywhere in the enclosure.

Hi mchad21,
Check under the heater box (where you were metering) It may be a metalic red button.

ok it COULDN'T have been that easy..

Found the red button. Pushed it in. It's more of a post not a button, but it is red.

The one thing I did notice is that when I pushed it in, and turned the heater back on, a red light on the control panel illuminated. Not sure what it is because it isn't labeled, but it wasn't lit up before (when the heater, or whatever, wasn't working).

And the terminal from the element is now energized...

Man oh man I think we found it !!

Hi mchad21,
Well it's kinda like we were saying last night.
Your mechanical thermostat stuck, and overheated the spa.
The high limit did it's job, and killed the heater.
Then it ran, and ran without power to the element.
Push the reset, and back in business.
NOW you can expect it to run maybe a week or less before acting up again untill you replace your spaside controller.

well, the temp right now is right around 90F. I will heat it to the same seting (roughtly) as I normally do to achieve 104F. If the thermostat doesn't kick off we get to 110F again, then the thermostat is the culprit.

Replace it and that's it. If it doesn't act up, well, it could have been my fault in that I set the dial TOO high. It doesn't take much and there is no digital display, only tick marks on the faceplate. It was dark...I was tired...heck I don't know.

Right (jeez I sure hope so)?

Hi mchad21,
Exactly.
If a spaside will maintain a preset temp in accordance with it's dial position, then it is a viable work around from replacement.
Technicly, if I see a spa side controller allow ANY thing over 106 degrees ( 104 + or - 2 Degrees) Then I must deem it faulty.
The Industry Standard maximum temperature for a consumer portable spa is 104 degrees F.

Keep an eye on it, and enjoy

I sure will. It seems like an easy fix to replace the thermostat, if need be.

I want to thank ALL of you for all your help. I learned a lot about something that was foreign to me.

Thanks again and I'll keep you all posted if I have any other issues.