JackMac

Thanks, I'll pull the valve and manifold again and remove that burner (and those either side) and see if that does it. If so, I'll let you know. It may be in the morning as the better half has me plowing the garden today. I decided to take the time to give the burners a shot with the air hose. I blew 150lbs of air into each burner, paying special attention to the the three below the igniter. The heater lit 3 times without failure. So, I'm hoping that was the problem, if not I'll do a thorough cleaning of the burners. Even if it continues to work ok, I will still pull the valve and manifold, remove and clean all the burners to make sure they're all clear. Thanks in advance for the advice . . . we'll see if it does the trick, I'll update later after I've given it a good (excuse the expression) smoke test. It's still giving me a problem. If I keep cycling the heater off and on, it will eventually light. Once lit it, will run until reaching temperature but not relight. Next I'll pull the manifold and the burners and check them for blockage.

Thanks, I'll pull the valve and manifold again and remove that burner (and those either side) and see if that does it. If so, I'll let you know. It may be in the morning as the better half has me plowing the garden today. I decided to take the time to give the burners a shot with the air hose. I blew 150lbs of air into each burner, paying special attention to the the three below the igniter. The heater lit 3 times without failure. So, I'm hoping that was the problem, if not I'll do a thorough cleaning of the burners. Even if it continues to work ok, I will still pull the valve and manifold, remove and clean all the burners to make sure they're all clear. Thanks in advance for the advice . . . we'll see if it does the trick, I'll update later after I've given it a good (excuse the expression) smoke test.

Thanks, I'll pull the valve and manifold again and remove that burner (and those either side) and see if that does it. If so, I'll let you know. It may be in the morning as the better half has me plowing the garden today.

No, once it's lit it will run until it reaches temperature, then it won't restart for the next cycle. But it tries to light, Yes? Thanks for the reply. The gas valve opens and the igniter comes on, but the burner doesn't light. It seems that the gas valve doesn't provide gas soon enough, only after the igniter has nearly dimmed out.

Cleaned the header and cleaned each orfice with a welder's tip cleaner.

No, once it's lit it will run until it reaches temperature, then it won't restart for the next cycle.

My LX400P 240vac Serial No. A99LE0181 (Propane, 2002 model) seldom lights. I have done the following: o Bypassed all safety switches to make sure I didn't have a safety lockout. o Installed new gas valve and bled line. o Measured demand voltage at gas valve (normal) o Measured gas regulator output (14"WC . . . top end for propane) o Measured gas pressure at valve output (on demand). Pressure present and drops to 7"WC (not unusual for an open line to the manifold); therefore, gas does flow into the manifold. o Removed and cleaned out the gas manifold and cleaned each jet's orifice. o Visually inspected igniter operation (using shinny metal plate as a mirror). Igniter glows bright orange when on. o The igniter resistance checks normal and I have cleaned the flame sensor. Results: o Igniter comes on and then the gas valve opens (verified by manometer). o Igniter goes back off gas valve closes. o Cycle repeats 3 times and then I get an AGS service code. Observation: o It appears that the igniter comes on, but there is a delay before the gas valve opens. The valve seems to open as the igniter has almost dimmed out. That is the reason I changed the gas line regulator, thinking it may be sticking and causing the delay. The regulator is connected to a high pressure line (10 lbs) and is located just outside the heater cabinet, so it's not a feed line problem. Questions: o Is this delay normal or maybe there's a normal delay, but maybe it's too long? The few times the heater does light it's just before the igniter dims out. The coincidence of gas and igniter seems to be right on the edge of the light cycle. o Possibly a control board problem? That's one thing I haven't changed out. I did pull the board, cleaned all the contacts, and insured that all wiring was sound. No change. o Finally removed all jumpers from safety switches since this didn't seem to be a problem. Gas valve and igniter still worked the same. Still won't light. Any suggestions appreciated and questions are welcome.

Tis OK. It just led to a little more checking to verify that it was the problem. I feel more comfortable placing the order now. So all is good. Jack

My experience with the LAARS LX400P: My heater (wired for 240vac) was intermittent and eventually would not light at all. It would give me an AGS fault indicator. I finally came by the LX Low NOx manual and was able to do some troubleshooting. I tested the safety circuits and they checked OK. Blower Pressure Gas Valve control voltage Ignition Control Water Pressure 28vac was being applied to the LP gas valve at the appropriate time and the igniter lit up, but there was no gas flow. I have a 15kw generator that runs off a tee on the high pressure side of the regulator and the generator runs ok, so I knew there was sufficient LP supply. The LAARS regulator is located right beside the unit. The heater worked last year, so I'm thinking LP pressure is still ok (no changes in LP plumbing). I assumed the valve was bad, but was hesitant to replace it due to cost and by forum comments saying that they never went out. There are no service resources within a reasonable distance, so I was doing this myself. I am a retired electronics engineer, so I'm comfortable with test equipment and circuitry. I'm saying all this to say that, out of desperation, I finally fired the system up again while monitoring the valve voltage. I waited until the purge cycle ended and the request for gas began. Then I took a solid state electronic service tool (small hammer) and tapped the side of the gas valve. Bingo! I got gas flow, the heater ignited and ran. I assume the actuator in the valve is sticking. I now feel that I'm justified in purchasing a replacement valve. I just wanted everyone to know that the valve does fail, although it probably is a rare occurrence. I can now add it to the many infallible devices that I've had to replace during my career. My thanks to the members of this forum and particularly of this thread. I'm impressed by the quantity and quality of the helpful responses here. The moderator and the contributors should be proud of the service they’re performing. It has truly been an educational experience. Jack