I recently acquired a mid-90’s Cal Spa hot tub. It worked when it was drained over a year ago, but after it was drained it sat unused until I recently began trying to bring it back into working order. It is on a 220 v dedicated circuit. The topside controls are air pushbutton. To date, I have replaced a split nut on the heater (which means I took the control panel off and then back on -- so I could have done something to cause my problems then), replaced one of the manifolds, and replaced the topside air control knob.

When I fill up the tub and turn on the jets, the water initially seems to flow fine, but within a minute or two water begins to exit the jets in pulses, and some of the jets do not seem to have any water coming out of them. I have bled the air valves on the wet end of the pump. Any suggestions on trouble shooting this problem?

I don’t know if it’s related or not, but the heater light is also turning on and off. The frequency with which the heater light turns on and off doesn’t seem to be related to the pulsing of the jets. Could this be the thermostat? The heater on this model is a 2" stainless flowthrough.

Likely problem: The pump is sucking in air- be sure theres enough water in the tub, might be too low. Check the filter compartment for obstructions, and be sure it's clean- if you have a weir door, be sure it's not stuck in the "up" position, or if you have a circular floaty thingee on the top of the filter compartment that floats to adjust to the height of the water, be sure it's working correctly-it might be stuck.
The heater light issue is related, and will go away once this is reloved.

You were right about air getting into the lines -- there were cracks around the housing where the filter cap fits in to the filter frame. I've cauked these and that seemed to help. Now that the heater light stays on I've discovered that the water doesn't heat -- guess I'll be buying an element.