Jandy LT 400L won't stay lit, Air Flow error

[Ron El Dorado Hills]

Hi
I am brand new to the forum today and I am not the most mechanical savy homeowner but I can follow directions.

I have a 28k gal pool with a spa that spills into it and a vanishing edge. We also have solar. Intelliflo pump and Jandy 4 cartridge filter system, Jandy vanishing edge to sheer descents pump, and jandy spa pump. 3/4hp booster pump to get the water up to the roof for solar. Zodiak iAquaLink to control pool with iphone. Polaris Cleaner

We hardly ever use the heater here in the Sacramento foothills and use the Jandy LT 400 maybe 6-10 times a year over the last 10 years that we've had the pool.
When I call for heat, the heater blower kicks on high then drops to a lower speed as it always has, the burners kick on, lots of steam comes out (it's been raining here), and just as (and maybe a split second before) the fan goes back to high speed, the burners kick off. It cycles 3-4 times an then quits trying, with then the Service and Air Flow leds blinking.

I went online and found a Jandy flow chart for troubleshooting. When I measure the voltage o the purple wire going to the pressure switch, I get 28VAC. This of course only when I fire up the heater. The flow chart then says to measue the voltage at the Black/Yellow wire. I'm not sure the proper way to do that. I took it off and it measure 0. When I put it on the spade connection on the back of the pressure switch an stick a meter probe in there, I still get zero. I checked the gray suction tube and it is quite pliable and new looking with no cracks or holes and it has a wire tie fairly securely holding it on at it's non-gauge end.

Am I trouble shooting this correctly? Is the best thing to do to replace the pressure switch. Any thought on other troubleshooting I can do? The air coming out of the exhaust is quite brisk and I found no significant leaves anywhere around the base when I look in the heater with the top off.









Thanks for your time.

 

[Pool Clown]

You should be getting voltage on both sides of the switch while hooked up and running (firing) or anytime fan has been running longer than 3 seconds. Best to check voltage at the safety loop terminal bar. That way, your checking the wiring too. Purple wire is power to switch, yellow/black wire is report. Check hoses for cracks (you did) AND obstructions, you will need to pull the hoses off and blow through them to confirm. If good, then sounds like air switch is bad.

ALTHOUGH, heater should not be getting gas valve voltage (fire) with no air switch conformation. Your symptoms suggest you are not getting flame rectification (flame proving rod). You also state that you are getting alot of steam, which would suggest a compromised exchanger (leaking). I would wait till the weather dries out a bit and check again for steam. Is the heater spitting a little water out the vent with fan on?

 

[Ron El Dorado Hills]

Thank you you so much for taking the time to reply. I'm not sure I know what a "safety loop terminal bar" is. The wires go back to the GUI into a connector with all the wires. What I'm thinking is to make myself a small wire jumper with a female spade connector on one end and a male spade (not sure of correct terms) so I can get my meter touching without taking the wires apart.
And yes, to answer your question, when the fan first kicks on it spits out a tablespoon or two of drops of rusty water as well as a fair amount of steam only when the burners first kick on. I took it to be because of all the rain we've had as well as the rust I see when I look into the flue vent.
I'm going to go check that gray tube again and pull it off to see that it is clear. If it is, since I have voltage on the purple wire, can I put a jumper for testing across the switch to see if the flames stay on?

 

[Ron El Dorado Hills]

I sent you a reply just an hour ago but have gathered a bit more info that I think could help.

I put in my electrical wire connector to go between the blk/yellow and it's attachment to the switch. No voltage measured there, with 28 still on the purple side.
Checked the hose and it's clear. When I put the fan end of the hose in my mouth and very gently suck I can easily hear the switch click. Also when I fire the heater and the fan kicks on I can hear the switch click if I put my ear to it. If I manually suck on the hose back and forth with the fan running, the switch clicks but no voltage on the blk/yellow side.

I have a question about the switch. Wanted to post another pic of it but the site says I've exceeded my capacity so I'll have to describe it. On the back of the air flow switch, on the left and right upper sections at about 11 an 1 o'clock are vertical electrical male spade posts.. The blk/yellow is attached to the left spade and the purple on the right. At the bottom is a third electrical male spade in a horizontal postion with nothing attached to it. When the fan kicks on this third spade has the 28 volts. When I suck on the hose I can get the 28 volts to go on and off with my suction. What is this third connection on the switch for and could I potentially use it as a new "report" voltage source?
Thanks

 

[Kiss4aFrog]

Welcome to the forum Ron

Just wanted to say hi.

 

[Ron El Dorado Hills]

View attachment 44988Finally figured out how to delete previous pics and add this one. The male spade that is at the bottom at the 6 o'clock position is the one I'm talking about. When 28 volts is at the purple and I put the meter on this third spade, it's voltage of 28 goes on and off with suction applied by mouth to the hose. Can I just move the blk/yellow to this spade connector?

- - - Updated - - -


thought I had it. This is the pic I tried to upload.

 

[Pool Clown]

Those switches can be used in 2 applications. IOW they can be used as normally open or normally closed. This is so the switch manufacturer can make one switch and satisfy either configuration.

One connector is used as the common (supply voltage), and one of the other 2 connectors would give you no voltage with fan off and voltage with it on, That's the way it should be used for this heater.

The third connector would give you voltage with the fan off then give no voltage with the fan on.

 

[Pool Clown]

Assuming that the air switch hasn't had it's connections played with (switched around), i think your problem is a leak in the exchanger from the info you gave in your second post.

The heater should be able to deal with water that may enter the exhaust via condensate drains, when it rains.

Given that your getting ignition, and the heater needs to have the air switch closed to do this, tells me that the switch is working. Flame proving rod perhaps failed when the exchanger started leaking and is no longer reporting properly, causing the heater to shut down shortly after ignition.

Unfortunately, you will likely need a service call to confirm this. If you are willing to tear the heater down to the exchanger yourself, that would save money/service call. Perhaps try to get a company that would be willing to give you a free estimate (i know, ha ha), but if you have them do the repair work, they might give you credit for the first visit.

You should be able to tear the heater down leaving the water system intact so you can run the pump and check for water leaks in the exchanger.