LARS LT POOL HEATER PROBLEM

Krypton · Dec 11, 2011

Hi Everyone

I am new to this forum as joined today in view of seeking help for my inground spa with a Lars LT propane heater.
I have had a some repairs done by pool company to the haeter and still I am having trouble when I come to use it weeks later.
This is what was done previously the main blower motor has been replaced as was faulty, then the pressure switch replaced, then the water temp thermostat replaced, which made the unit work ok until now.

Now when I switch on at the control panel for heat to the spa, the burner shows a SERVICE and HI LIMIT light on and nothing works on the heater.

I need to know if I can check some things my self as I have been constantly paying for call out and unit then malfunctions after using it once or twice.

I have electronic experience and can use multimeters to check volts and check components for short/open ccts.

Hope someone may be of help to my problem solving my heater.

Cheers

Ameer

Boland01 · Dec 11, 2011

Check your high limit switch. I've had to replace mine a couple times in 7 years. Both the 150F and 135F switches are located underneath the main inlet and outlet on yours Laars. You can pick them up off of ebay for around $30.00 each.

Krypton · Dec 12, 2011

HI
Thanks for your help, my guess was eo replace them as well so might as well do it since the unit is a few years old.

I will order them today and will report back if that solves the problem.

Cheers

Ameer

spishex · Dec 12, 2011

Those high limit switches are wired in series so if you pull the two wires from the board that are labeled "High Limit" you should have continuity across them. If the circuit's open then one of the high limits isn't closing.

Krypton · Dec 17, 2011

Hi Again

I replaced the the high limit sensors in my Lars LT heater today, and started my spa ( NO MORE HI LIMIT FAULT )and called the heater for heat on demand. The control panel in my house showed the red light that heater was active, but no heater came on. Waited for a while and then the service light came ON flashing with the AIR FLOW light.

That kind of sucks now as I have another problem which was inherent to the heater.

Service light and AIR FLOW are flashing together, so does anyone have a clue as to where I should now check to see what is causing this fault.

As always greatly appreciate your help so far.

Cheers

Ameer

spishex · Dec 20, 2011

This is a problem with your airflow or the switch itself. Check to make sure the fan is coming on properly and that it's intake/exhaust are not obstructed. Be sure the blower pressure switch tubing is not broken or crimped. When the fan is on you can check for continuity across the blower pressure switch wires (black/yellow and purple wires next to all the white high limit wires on the board).

There's also a manual reset high limit for your vent stack which is on the two white wires immediately next to the blower switch wires. I'm not sure that you'd get the same error from that but I'd check continuity on that circuit just in case. It should have continuity all the time. The fan switch will only close when the fan is on.

Krypton · Dec 20, 2011

HI

Thanks for the input. How do I check the fan motor to make sure it is not faulty? It is not coming on and thats why the pressure switch is not responding.
I guess the fan comes on first to create a vacuum on the tubing and closing the switch, which then sends signal to the circuit board. That is not happening at this point.

PS Fan motor was replaced about a year ago, and today I replaced the run capacitor to eliminate that just in case it was dead.

The motor has the following color wires
white, black, blue, red, orange.

Is there a way to check the motor outside the unit to see it is running correctly?

Appreciate your help

Ameer

spishex · Dec 20, 2011

There's an in-line fuse in this heater (you'll notice a bulge the size of a small fuse in the middle of one of the wires). Track that down and make sure it's not blown.

I don't have any info on the wiring to the motor, unfortunately. From the wording in the manual it sounds like a convertible motor so the power to it should match your incoming power. If you're setup for 230v you'll have an easier time checking to see if it's getting the necessary power. It looks like the 15 pin connector goes to a terminal block that then feeds the motor plug. I'd check to see if you can find 230v across any of those five terminals when the fan should be coming on.

peterlarson · May 10, 2017

I have a HI temp error, but, I am having trouble finding where you get access to the HI-temp switches on a LAARS LX400. Do you remove the panel under the water intake? After finding and removing the Hi-temp switch, I discovered that they installed only the 150-30 hi-temp switch and the 135 hi-temp switch is not there or installed and the current harness does not have the extra sleeve for the 135 Hi-temp switch. The circuit board does not have marking for either switch, just two terminals hooked up to the 150 switch. Does it make sense to order the new harness and install both switches at this time? Is there a risk without having the 135 switch. The current heater with only the 150 switch has been installed and operation for over 10 years without incident other than the 150 hi-temp switch just failed??? I hesitate to change the configuration by adding the 135 switch since it has worked for over 10 years. Anyone have a perspective on the risks??