I have acquired a used Dimension One spa. The previous owner had replaced the circulation pump with an aquarium pump. He routed the output of the air pump directly to what I believe is the Ozone bleed off (for excess ozone) area, which is located just behind the skimmer. I can see bubbles come up through this area. I do not see any bubbles coming into the main tub area.

I am getting a "FLO" error message causing the heater to not turn on. Both jet pumps work fine but I am not understanding how FLO is to be achieved. It seems to me that I'd have to use this small pump to move air/water into the main tub area. Can anyone tell me where the output of this pump should be plumbed?

I am assuming when you say an aquarium pump you mean an air pump, and that isn't used for circulation, but to force air into the ozone generator so the ozone makes it to the tub, and the way you have explained it's routing, I would assume they are bypassing the ozone generator all together.

If you have a low flow heater, you will have a separate circulation pump for the water, and it a little larger than a popcan. If you have a flow through heater, it will be driven by your low speed jet pump. Either of which needs to have enough flow for the flow switch to operate. Either you don't have enough flow, or your switch is defective.

I have a Dimension One Chairman, a 1992 model I believe. I'm not sure which style of heater is supposed to be in it. I can say that the heater has an input from the tub and outputs back into the tub and no other connections except for the pressure switch which is mounted on the heater itself. It looks like the tubes running to and from the heater go into the tub, from the side of the longer section of the tub. These 2 outlets do not appear to be jets as they never "come on" as both jets are turned on so I'm guessing that these are in and out of the heater.

Looking at the electrical schematic in the owner's manual I only see the 2 main pumps (jet - 2HP) and the small pump for the ozone section. Should one of the 2 large pumps being running at a low speed and maybe it's not?

if your heater has 1 1/2" lines going to and from the assembly, it will be a flow through style, and will be driven by one of the jet pumps on low. The heater MUST have a pump to feed it.