Laars LT 400 Pool Heater Water Pressure Switch

[Boland01]

I've got a Laars 400LT Pool heater. A couple of weeks ago we were heating our spa and the heater stopped working when the spa water hit 93F. The cutoff is is 101F. When I tried it again today, I do hear a click and the water pressure switch flashes on the control panel. other than that there is nothing. I tried adjusting the valve counter-clockwise but it still just makes a click sound in the heater and then the pressure switch light flashes. No other lights on the control board flash.

From reading some of the other forum entries I'm guessing it could be a bad pressure switch. Is there a way to bypass or test the switch to see if it is fact at fault? I did pull both connectors and put a jumper wire between them bypassing the switch completely but still no difference. Any other items I should look at? I really don't want to blindly start throwing parts at this. Thanks in advance for any direction anyone can provide.

 

[ps0303]

As a test, you can remove the two wires going to the pressure switch and insert a jumper wire between the two ends. Then turn on the heater and see if it lights. Also, make sure you have a clean filter as well. If after you cleaned the filter, you still have this issue then you can pretty much be assured the pressure switch is bad.

 

[Boland01]

If that doesn't work any advice on what to check next?

 

[danpik]

Does it say "water Pressure switch" or just "pressure switch"? There is a pressure switch that is used on the exhaust blower (technically it is a vacuum switch) that can go bad as well. Also, the way this looks to be wired it may have a system in place to look for an open switch at startup. On the water pressure switch, this is not applicable, but the pressure switch for the exhaust on some newer systems it looks for an open switch prior to startup to verify it has not been jumped out.