I have a Caldera 220v. hot tub.
It has a 2 speed pump, which I had professionally rebuilt and new seals just 4 months ago.
It's been working great until 3 days ago. It was making a loud clicking, like a relay sound, every 3 seconds or so, and the light for the heater was going on and off with the clicking. The light up on top, that is on the thermostat stayed on, thinking the heater was on.The water was slowly getting colder.
Then the heater would not come on at all the next day.
I assumed something was going wrong with the heater, but the wierd thing is that when this started, the pump, although working on both speeds, wasn't putting out any pressure.
On high speed, it puts out like the low speed should normally.
ON low speed, you can't even see the water move, you have to put your hand in front of the jet to feel it.
I had some leaves in it, and thought, maybe it sucked some up and was blocking it, so I pulled out the pump and heater section and put a hose in and ran water backward through the system, but nothing came out but water.
I reinstalled the pump and it's the same. I checked the two wires at the heater and they each have 110v.
The control box says model EM-190
It's an Aquaflo 2 speed pump.
The heater is the wtraight, flow through, stainless steel tube with the element inside it, and it's on top of the pump

Thing is, regardless of the system, you've identified the pump as the culprit. If the motor is turning, and you're getting low flow, then something is screwed up in the pump wet end.

Pull the pump, remove the 8 screws in the face plate and examine the impeller for anything stuck, or... for that matter, be sure the impeller also turns with the motor shaft.

Then you can move forward.

you were right, I pulled the pump, and it was chock full of leaves. I cleaned it out and shazzam, it started pumping and heating.
Thanks for the help.

Awesome. Good to see that simple stuff works.

it worked for about 2 weeks, then the heater would only work when the pump was on high speed. Now the heater doesn't come on at all.
I used a meter to check voltage, and when i turn the switch to heat I can hear the relay click, but the lower light that is connected directly to the inline heater does not come on. However, the heater has two wires connected to it and both of them have 120 v.
The pressure switch has no pwer to it until the relay clicks, then it has 120 v. to both wires on it too.

You should only measure your heater (or pressure switch) voltage ACROSS the two terminals - never measure terminal to neutral or ground.

I think your pressure switch setting is marginal... you may want to try rotating the adjustment thingy ccw a turn to see if that helps.