Jandy heater blower pressure switch replacement?

[rhythm]

Hello,

I am getting ready to purchase a new blower pressure switch for my Jandy LX400 heater, but I wanted to see if I could get some advice here first. When trying to use the heater I get an 'air flo sw' error on the screen and it shuts down. But the blower appears to be working perfectly, the rubber tube is in great shape, and there is nothing blocking the exhaust air. The gas even ignites and I get heat for a little while before the shut down.

I'll hear the blower on at high speed for a while, then at lower speed for a while. Then the gas kicks in and is lit. I'll feel hot air from the exhaust port. The fan goes to high speed again, and back again to low speed after a little while. Then the error message appears on the screen, the heat goes away, and eventually the fan stops as well.

According to a troubleshooting guide I found, either the fan pressure switch or the GUI is at fault. There are some voltage measurements I can take to try and determine which is at fault. Based on the symptoms I'm describing, does anyone here know right off whether or not I should be replacing the fan switch? If I do the measurements, I'm assuming that I need to do them while the heater is trying to come on and heat the water, rather than being static?


Thank you,
Greg

 

[rhythm]

Well, just to update things, I'm thinking now that it could be almost anything that's causing this. Because the gas flows and ignites and I get heat for a little while, that must mean that initially all of the safety switches are closing. So something is happening once the fire is lit and the water is starting to get heated. I imagine at this point it could be anything from too much soot built up in the heat exchanger to a bad flame detecting rod. Oh, and the last time I tried it, the fault code reported was 'AGS', not 'Air Flo Sw'. So as I said I think anything is fair game right now. If any of you have experienced this, where the heater does initially start up OK and gets heat, but then cuts out, I'd love to know what fixed it for you.

Thank you,
Greg

 

[ps0303]

If it was an air flow switch error and the tubes and switch are good, I would inspect the blower motor and confirm is is in good shape. I would still double check that anyway to make sure it is in fact in good shape. The AGS error could indicate a gas pressure issues, oscillating pump pressure, or it didn't light. I would guess the first two might nor be your issues. You could try cleaning the flame sensor or replacing it.

In case you do not have the manual for this unit.

https://www.parts4heating.com/v/vspfiles/images/pdfs/JandyLXLT.pdf

 

[danpik]

How long is "a little while"? This will help us. Is it 5 min or 5 seconds