I searched the forums and could not find this issue anywhere...

I have a two year old Jandy LT heater using Propane. When this unit was new I had a problem with the heater but don't recall the issue as they fixed it right away under warranty. Today I tried to use the heater after not using it for a few months and it's not working properly.




Here's what it does:

Turn on Heater


• High fan comes on for a few seconds, then
• Low fan for a few seconds, then normal ignition.
• A few seconds after ignition, the high fan comes back on.
• In less than a minute the fire goes out and the cycle happens again.

After two cycles the "Service" and "Air Flow" lights come on.

So it seems that I have an air flow issue. I take off the case and inspect the exhaust and intake areas and both are completely clear, I checked the hose that connects to the vacuum switch, when the fan is running there is suction but I couldn't tell if it's an appropriate amount, but when I disconnect the leads on the vacuum switch and connect a VOM it looks to be activiating with the available suction when the fan is running. So it would seem that there is enough vacuum to activate the switch.

Any Idea why else the "Air Flow" service circuit would be activated? or any idea what other tests I could try?

My next step is to call a pool place to look at it, but I like to do repairs when I can and figured I't troubleshoot for any easy stuff on my own.

Welcome to the forum. I can be of no help on your dilemma. What about the tech support people at Jandy before you call a pool guy?

Something is "tricking" a sensor in there but I have no experience dealing with them at all. Good luck with it...Let us know what it was when you find it.

I had a different problem with my LT this weekend and managed to locate the troubleshooting guide at:

PoolCenter at Ideal BB

My problem was the "ES 1" light (Extra Switch 1), which turned out to be the Flue Vent Temperature Limit Switch (manual reset). The troubleshooting guide gives you several items to check with a voltmeter. Having an exploded view of the unit also helps, because neither the guide nor the manual tell you where to find everything.

As always when dealing with gas appliances, be careful. Depending on your setup, you may need to have the filter pump running in order to provide power to the unit when checking voltages.

For future reference, the resolution to my problem was to clean the leaves out of the flue and reset the switch (manually, of course).

Good luck.

Thanks for the link to the troubleshooting guide, that may come in handy. According to the guide and the testing I've already done my problem is either the Air Pressure Switch or the GUI (it doesn't say what the GUI is, but from the photo it looks to be the computer)

I contacted a Jandy authorized service guy to come out but it turned out that I was outside his service area, he did give me a few ideas on the phone. He said to clean out the basket and filter (I did, and the filter was pretty dirty) He said that low flow can cause the water to move through the heater too slowly and that will trip the overtemp switch and shutdown the unit.

After re-reading the manual that theory doesn't seem likely, but now I noticed something else, my system has three of the anti-backflow or check valves with the clear tops. My jet pump and my water feature pump valves are fully open when the pumps are operating but when my primary pool filter pump, the one that goes through the big filter and the heater, the flap on that valve is only open about 1/3 of the way. I've never noticed it's position before and am wondering if it should be fully open.

One last bit of bad news, I found a bone in the basket of my primary pump, it looks like a rabbit leg bone. Although it must have, I can't imagine my crawler picking that up, and it doesn't float so the skimmer probably didn't do it.

Could I have more critter in my plumbing?

Lastly I am posting a copy of the Jandy LX/LT Troubleshooting guide in case anyone else needs it.

An "anti-backflow valve" is normally called a "check valve". Check valves can get stuck when some debris gets caught up with the flap. It is typically fairly easy to open them up (with the pump off) and clean them out to restore smooth operation.

If something was blocking the water flow I would expect it to give you a different error light.

GUI is "graphical user interface" in the computer world. In this situation it is presumably the computer and display board.

If the heater is actually firing, you have some sort of flame rectification issue. It would not fire if this was a straight air flow sensor deal. The air flow sensor will trigger for insufficient vacuum and that diagnostic is only associated with the vacuum switch. The key is insufficient vacuum. You may have a small chew mark from a rat in the fan tube to cause it. But, if firing and then going off and retrying before lockout, that is a flame sense problem that would normally trigger the AGS diagnostic. You should be getting 4-7 micro amps at the FS lug on the gray ignition box. You also need to check the integrity of the bonding to the heater, the ground to the heater and the burner ground wire. a loose connection will break the circuit but that would still throw the AGS code and not the air flow code. Try jumping the air flow switch out of the circuit and see if it shuts off.

Thought I'd come back and post the solution so that anyone with the same problem could see what I did. It turns out that the propane pressure was wrong for some reason. I suspected low pressure so I adjusted my regulator up and tested the heater, after several tries the heater started working normally.

My plan was to adjust the pressure up for several tries and if that didn't work try lowering it, but the problem was low propane pressure and everything is fine now.

Thanks for all the suggestions.