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Laars LX400 Heater problem

16 years ago

I have a Laars LX400 heater that will not start. The heater has not been used in approx 8 months. The error message that appears upon start attempt is "Low Pressure" The company states that that error is a water flow problem and perhaps the pressure switch is problematic since water is clearly flowing through the unit.

Does anyone know how to troubleshoot the pressure switch?

Thanks,

BT

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Comments (10)

Rack Etear
16 years ago
It's tough on the LX to trouble shoot the pressure switch without replacing it. IIRC the threads for it are proprietary.

You can pull both of the wires off the switch, and do a continuity test on it. If the circuit is closed the pressure switch is fine. If its open you either have a bad switch, dirty filters or and obstruction in the water flows somewhere.

The LX was just about one of the worst heaters I have ever encountered The burner trays on them melted like crazy even on systems with excellent gas pressure.
btlt
Original Author
16 years ago
So are you suggesting that I replace the pressure switch?
If so, do I simply unscrew the cooper tube and pull the wires and reconnect?

Then I should be good to go, right?
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repair_guy
16 years ago
How about a filter clean first. You must assume the switch is doing it's job first and then assume it's failing. If you have not fired the heater in 8 months, I'm guessing you have not cleaned the filter in that time. If flow is good then the switch is bad.
btlt
Original Author
16 years ago
Even with a clean filter, the heater will show a low pressure error. That is why I believe it is something else. The company said the pressure switch is most likely the cause. However, it just doesnt seem to be likely to fail especially with no use in 8 months. Anyway, I will order a ps and replace it. if it still shows error, what are your recommendations?

Thanks for the help so far.
BT
repair_guy
16 years ago
OK, if the filter is confirmed clean you have two possibilities. Blown fuse or bad switch. Check the inline fuse
and if it's blown you need to see why it shorted. Rats?,etc.
If the fuse is good, it's the switch. Switch is part #R0013200
Rack Etear
16 years ago
If the fuse was blown, you woudln't get anything on the display.
poolexpert
16 years ago
LX/LT HEATER SERVICE DIAGNOSTIC GUIDE
DISPLAY CODE CAUSE REMEDY
PRESS SW *
(pressure switch)
1. Pump is not running. 1. This is a normal display when the pump is OFF. No
Service Required.
2. Low pump pressure. 2. Clean filter or clear blockage/check position of valves
in plumbing system.by pass?
3. Device connected at "Fireman
Switch" terminal block is open.
3. This is a normal display when a device connected
to the "Fireman Switch" operates to open the
safety circuit on the heater.
4. Pressure switch fault. 4. Adjust or replace pressure switch.
Refer to qualified service personnel.
repair_guy
16 years ago
racket, the GUI on the LX is a 12 volt system on the transformer side. If the board were to die how could you get a
low pressure code when the inline fuse blows?

The integrity of the fuse gives the completed 24v circuit down the red wire for the safety loop
Rack Etear
16 years ago
I thought the fuse powered the board also.

Personally I havn't met an LX that I havn't had to replace.
John Kelly
6 years ago
Test

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