Spa Blower turns on by itself

[K G G]

Good Afternoon,

We have a Spa/Pool combo, about 6 years old. Lately the spa blower motor (Air Supply Silencer Air Blower) turns on by itself and only a reset of the pool pumps fuses shuts it off.
We have no remotes or complex electronics, just a plain old dial for the pool pump and a dial for the vacuum.
The spa blower is typically triggered by a vacuum switch in the spa itself. The latter has been replaced twice to no avail.
What could the cause be?

 

[JamesW]

What model pressure switch is controlling the blower?

Is the air tubing exposed to sunlight?

Does the air tubing have water in it?

 

[ps0303]

I bet there is water in the airline. Blow the airline out.

 

[K G G]

The attached picture shows the switchbox at the termination of the airline. The inside of the box are clean, no corrosion.
No sunlight hits the air line ever.
How to blow it out?

 

[ps0303]

Disconnect both ends, be careful on the spa end so it doesn't slip back into the hole, and then blow compressed air thru it.

 

[K G G]

Thanks everyone. Disconnected and rerouted the SPA end to avoid it slipping in the hole (happened a few times b4). Basically drilled into plastic tube from above and made a small, loose knot.
Then used compressed air to blow out the line (disconnected at both ends).
Then also drilled two very small holes into the line about 6 inches from the wall switch (reco by manuf.).

So far so good

 

[JamesW]

Was there water in the tube?

 

[K G G]

No noticeable water in the tube, which runs about 100ft under ground, and just before the weekend the spa turned itself on again.
Manufacturer recommended two tiny holes in tube near switch, that however made the push button useless. Taping the holes shut made spa button work 50% of the time. However if I blew into the tube heavy enough the switch operated as intended.

There was no way to pull a new tube thru the piping (assuming some 90 degree angles underground somewhere, so I ended up running a complete new line of tubing (irrigation type) from the wall switch to near our spa and buried it under the grass, using original spa button. Now it works flawless.

If this eventually gives up I am not digging/burrowing another line and will probably look for an electronic/remote option.

 

[ps0303]

I would suspect that there is something in that old line causing this issue. A small amount of moisture/water can cause strange things to happen.

Actually it is very easy to pull these lines thru. I've pulled some very long lines with ease.

The new line should work for a long time until it get moisture in it.