What he said. Again, a picture would help here. You may have one pump that works and another that doesn't.

Where do I go from here? No obstructions, not the filter, it's downstairs humming along, as long as I want a nice cold soak I'm in good shape.
Thanks again for any ideas.

First, I want to thank every one who helped me get up and running. It was "pure and simple" a flow problem. But it was far from simple. After checking every darn place I could see, I realized that there was a "kink" in the flex pvc running from the filter. When cut the section out, the inner lining had collapsed. Replaced that section and I'm up and running great with good flow, etc. Thanks again!

Now my new "issue". I am running the AP-4 without a topside. A bit inconvenient, because I have to either leave the side off the tub (it's in an enclosed sun porch-so no weather worries-but the cold!) or remove it to change any functions.

So I "treated" myself to a new topside. I haven't installed it yet because it requires a thermowell which I don't have. I could drill out for one in one spot but I think I'm in over my head.

Is there any way to work around this? Any thoughts?

Thanks for your help in advance.

It's very easy to put one in the side of the tub. You can install one in your plumbing, but the PVC work is much more complicated. I think you'll need a 1 1/8" paddle bit for a standard through-wall thermowell? Check with whatever one you come across, it should tell you in the packaging. Next time you have the tub empty drill through somewhere at least 6" below the water surface and easy to access from below.

Well, here I am a couple of months later with my tub up and running great and my new topside on the table in the living room. After much thinking, I decided that I just couldn't take a drill to my tub for the new thermawell, I'd rather chicken out and add it to the PVC piping. (I know, I know) Since I did all the PVC for the tub I've got plenty of room and I've become quite good at the plumbing stuff. Now, I'm here feeling like a fool. I've got the PVC thermawell and can't figure out how to get the thermostat probe in. Do I just squeeze it through the little rubber gasket? I'm afraid that I'm going to rip it apart. Thanks so much.