Jandy LXi - Fault High Limit

[Easto]

I had a guy come over and he shorted the sensors and the heater fired up right away.

It is a 10 year old heater and he said I could have received a bad sensor that died OR there is some other issue within the heater that’s caused the sensor issue.

I can try to replace the sensor and see if that works, but the heater is reaching the end of its life and may just need to be replaced.

I’m looking at $89 for a new sensor and see if that’s a fix, even temporarily.

Or a new heater.

I’m not a completely comfortable trying to short wires and stuff like that. Basically I don’t know how to do it, so my trouble shooting doesn’t get too technical

 

[mtesh73]

After poolclown's help last year diagnosing a similar issue and replacing several sensors thinking they may be bad from the factory and trying to jump them with resistors all to no avail. It turned out to be a board issue. I sent it to the gentlemen recommended here in a previous thread, got it back in a week, right after I closed my pool for the season. Installed it last fall, heater kicked on this spring like new.

 

[Rossterman]

You installed 2 new sensors Of the 4 that could Be bad . Using a short jumper wire it is easy to narrow down which one (high temp, low temp, exhaust gas, and air press). I thought the same thing (16 year old heater) but it runs great again for pennies compared to the price of buying and installing a new one. Here’s my plan:

The high/low temp harness should plug into a wiring connection prior to the control board. Disconnect there and place a jumper wire between the two connectors on the circuit board side. Run heater. If it works fine its a bad wire or sensor (sometimes new ones are bad).

If still behaving the same, reconnect wires and move on to the exhaust hi temp limit switch (the one that can be reset), remove the two wire leads and jump across them. Run heater and see if it works OK,

if not, plug back in and go to the air pressure switch (round one with the hose connected) and run heater. When fan starts jumper across the two terminals (not before). If it doesn’t run OK Than the board is the likely only other issues.

remember that the electrical signal is 24vts a/c which doesn’t shock you like playing with live household wiring but you still want to take normal caution and not Ground wires to the chassis accidentally).

 

[setsailsoon]

I had a guy come over and he shorted the sensors and the heater fired up right away.

It is a 10 year old heater and he said I could have received a bad sensor that died OR there is some other issue within the heater that’s caused the sensor issue.

I can try to replace the sensor and see if that works, but the heater is reaching the end of its life and may just need to be replaced.

I’m looking at $89 for a new sensor and see if that’s a fix, even temporarily.

Or a new heater.

I’m not a completely comfortable trying to short wires and stuff like that. Basically I don’t know how to do it, so my trouble shooting doesn’t get too technical

Easto,

First, let me say it's good to know your limits. Safety always requires we know our limits. I have no idea what the condition of the rest of your unit is and if it truly is real bad maybe it's time. If it were me I'd probably try to squeeze a few more years even if I had some more repairs. This is a personal call and there's no right or wrong. If you don't want to mess with this type of repair. each year I'd replace. Your at the stage where this kind of thing is likely to happen every year from here to the end.

I hope this helps.

Chris

 

[Pool Clown]

One needs to consider that perhaps the high limit is working properly and that your heater is in fact overheating. Especially after you just replaced the part, and the problem persists...

In the time i have been in this industry, i cant remember ever having a failed hi limit right out of the package, let alone high limit failures to begin with. However, with the advent of the internet and most parts having a Chinese knock off, perhaps the failure rate of those parts have gone up. That is why it is important to get factory parts even if it means paying a little more.

Some Jandy/Laars heaters have plugs in the header for the installation of what they call a "Petes plug". These allow the water tight, temporary insertion of a temperature probe so you can monitor the temp change or "delta" of the water as it either makes a first pass or total difference through the heater. This may give you a better idea of what is really happening, if its the electronics, or if the heater has a flow issue.

 

[Easto]

The brand of sensor I got was Zodiac from Amazon.ca

I’m not 100% sure where I find the gas exhaust or air pressure sensors.

i also couldn’t find any tutorials online

 

[Rossterman]

Here’s the better of The troubleshooting guides but neither are that good. The bypass Test method is much simpler. The exhaust hi limit switch is inside the cabinet just above the black plastic water manifold (where you put the new sensors). Just remove The contol paneland its easy to access. The pressure sensor is even easier to find it’s behind the metal front panel that slides down when you remove the side cover. https://www.jandy.com/-/media/zodiac/global/downloads/l/l0747.pdf

 

[Rossterman]

The exploded parts diagram shows locations of everything.

 

[Rossterman]

Hey, just noticed your title Is an lxi not lx. Slightly different location of some parts be very similar regarding troubleshooting. Here’s link to parts locations in the diagram Jandy LXi Low Nox Gas Heater (2008–Present) Parts - INYOPools.com

 

[Easto]

So if the high limit sensor was jumped and the heater turned on, that doesn’t necessarily mean the sensor is bad?

One other thing I came across in my research is the potential for the brass high limit plugs could also be corroded. Is that something I should be concerned about?

 

[Rossterman]

If you jumped the sensor loop and it runs try just bypassing one sensor at a time to find out which one is the problem then get amazon to replace it. BTW the LXi doesn’t appear to use a high exhaust temp sensor and the air pressure sensor is on a separate loop so it’s likely just a bad new sensor (that happens from time to time)Sounds like you are almost there!

 

[setsailsoon]

The brand of sensor I got was Zodiac from Amazon.ca

I’m not 100% sure where I find the gas exhaust or air pressure sensors.

i also couldn’t find any tutorials online

*** Edit - sorry I had typed this earlier today but did not press POST. Operator error on my part.***
Easto,

I read your reply to indicate you're not comfortable doing the trouble-shooting. I'm still a little confused if that's the case or not. If you or your friend are comfortable here's what I'd do. There are two sensors in the circuit. I believe one is set at 135 deg and the other is 155 deg. They provide "double protection" to keep your heater from going to high on outlet temp. T Remove the connectors at the sensor and check for a short with the heater off and cold. If it reads shorted it's bad and needs to be replaced.

The only way a heater can normally get too hot is with low flow and/or a thermostat failure. But it sounds like yours fails from the very start before it even heats up. This leads me to think the sensor is bad.

I hope this helps.

Chris

 

[setsailsoon]

So if the high limit sensor was jumped and the heater turned on, that doesn’t necessarily mean the sensor is bad?

One other thing I came across in my research is the potential for the brass high limit plugs could also be corroded. Is that something I should be concerned about?

Easto,

I think you have the problem isolated to one of the high limit switches. Check them individually and then replace the defective one. If your heater fires normally with both of them jumped then you know there's nothing else wrong. All you need to do is figure out which one is bad.

Chris

 

[Easto]

I don’t want to come across as stupid, but how do I jump each switch?

do I remove the sensor (example 135) then with the exposed wires, touch them together to make a circuit. If that solves the problem I can say the 130 was the problem.

if not do the same with the 155 and hope one of the two turns the heater on?

if I take the sensor off, what exactly would I Need to do to jump this?

 

[setsailsoon]

I don’t want to come across as stupid, but how do I jump each switch?

do I remove the sensor (example 135) then with the exposed wires, touch them together to make a circuit. If that solves the problem I can say the 130 was the problem.

if not do the same with the 155 and hope one of the two turns the heater on?

if I take the sensor off, what exactly would I Need to do to jump this?

Easto,

You've got it! Just touch them together. Most of the time it's easy to make a jumper wire with a spade terminal at each end or just remove the wires and put a piece of wire with the bare ends in each wire connector. This wire "jumps" from one wire to the other. This simulates a normal water temperature. When the temp heats to an unsafe level the switch inside "opens" the circuit. You do have to be careful the heater is not actually overheating and the switch is not actually functioning properly to avoid an overheated unit. But if you can't even get the heater to light that points to the switch and not a real over-heated situation.

Chris

PS there are NO dumb questions.

 

[setsailsoon]

Just to be clear the wire should be black and connect at the ends to the blue terminal on the control board as shown in the diagram in post #11. If for some reason your board does not look like this let me know before you do this.

Chris

 

[Easto]

I’ll take a couple pictures in the morning to confirm.

What I was going to do is take the 135 and 155 sensors out of the harness.

Then make a connection between here to hopefully get the heater to fire up.

 

[Pool Clown]

Preface.
I am under the impression that the heater fires, runs for a bit, then shuts down? If this is not the case, and if this heater will not fire at all, disregard the following:

Jumping the high limits is no way to check them. All you are doing by that is taking the switches out of the equation.

Have you run the heater with the sensors out of the heater like in your two previous pictures, with the sensors still connected, but in your hand? I would run the heater just like that. Dont short the switches, just leave them connected and let them hang, preferably out of direct sunlight. This will tell if the switches are bad. If the heater continues to run with no issues then i would suggest that the switches are ok. If it shuts down after a while, look at the switch that opened.

Note:
Do not continue to run the heater with the high limits removed from the wells. Doing so may allow the heater to run unchecked in a over heated state.

 

[Easto]

I turned the heater ON with the switches removed from the well.

heater doesn’t fire up.

As soon as I set the heater temp higher than the water temp (to signal the heater to turn on) the Fault shows on the screen. The heater doesn't even try to turn on. I’m assuming that means that the sensors are most likely not working properly.

but I am just making an assumption

 

[Rossterman]

I turned the heater ON with the switches removed from the well.

heater doesn’t fire up.

As soon as I set the heater temp higher than the water temp (to signal the heater to turn on) the Fault shows on the screen. The heater doesn't even try to turn on. I’m assuming that means that the sensors are most likely not working properly.

but I am just making an assumption

Ok, now one at a time, jumper each and see if it will start and run. That will help you isolate which is bad.