H400idl2 not firing up

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Seanboy said:
Ok, so here goes.

I replaced the cap and although the blower seemed to spin right up and at a faster pace than previously, I still got the AO code. I anticipated this though so I also installed a new blower switch. This seemed to do the trick because it fired up on its own for the first time without me blowing/suctioning on the tube.

The only problem is after 30 seconds after the heat light turns on (also get a nice bright orange from the peekhole) the heat turns off. But.. it will re-ignite again right after and 30 seconds it will lose heat again. So I get good heat from the peek hole and the green heat light on the control panel is on for those 30 seconds, but it stays in this loop with no error code. I let it go about 10 times in a row. Heat for 30 seconds then off and re-ignition then another 30 seconds.

What do you make of this one? I'm so close, I can almost taste it. Haha
Click to expand...

So it is igniting the gas but not staying lit, correct? If so, I would remove the flame sensor and use some steel wool and clean it. That might take care of the issue. If not you would need to replace it. What seems troubling is that the unit should be giving you a IF error code.

Getting close!
 
Ok, so I cleaned it off and screwed the flame sensor back in. I let it run by itself about 11 times without touching anything.

Try 1, lit up and ran for about 60 seconds then flame turned off
tries 2-5 lit up and ran for 30 seconds before kicking off
tries 6-8 - did not ignite
9-10 lit up and ran for 30 seconds
try 11, 30 seconds then kicked an IF code.

I also used a known good board to test. Here's a video of attempts 9-10 if anyone see's anything strange: View My Video
 
There is a temp sensor and then two temp limits on the header. I do not suspect those to be the issue. I watched your video and I see you have a new ignition control board. Did you get the correct one? There are two different boards. One for the model heater you have and one for the newer FD units. The fact that you finally go the IF error code could still be the flame sensor or the ignition control board.
 
The tag on the control board #'s matched up with the existing board so I believe it should be the same. Unless there are 2 boards with the same product #. I am hoping this doesnt come into play, but ever since yesterday when heat started passing through the system, i've got a new leak on the water side of the heater. I'll attach the video.

Should I proceed with the new flame sensor, or could this new leak be the cause?View My Video
 
Looks like the header is cracked. I see water dripping from several spots. One spot could probably be resolved by tightening up the unions. The other one looks like it's coming from a crack in the header. If the header is cracked you could look to find a replacement one but you are starting to get into an area where you might want to question how much more you want to mess with the thing or just replace it.

If the heat exchanger is leaking inside the unit, it could be the cause of why it won't stay lit.
 

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That's what I was thinking as well. I'll give the flame sensor a shot and if that doesn't work, I'll have to take some time and consider my options. I don't want to put to much into an older heater
 
The new flame sensor will be here tomorrow and i'll take a look. From there i'll get a good look at the cracks and possibly give the heat exchanger a go with a welder if that's the last issue. I don't think I will be buying any more parts for it though. I'll keep you posted and thanks again for continuing to help out, i've certainly learned alot in the process.
 
Well after taking the cover off above the header, I could see if was only leaking from the seal. I tightened the header bolts and no more leak. Hopefully it stays gone.

Still continues to cycle heat every 30 seconds so we'll see what the flame sensor does.

Btw, was there any way to test the sensor?
 
Also, one more thing to rule it out. I pulled all the orifices and they were all clean and clear.

I did notice tonight due to the first time working in the dark that at the end of the 30 seconds when it shut off, it was always immediately after I saw the slight flames from the vent.

Heats for 30 seconds, the blower kicks into high gear, I see the blue flame out the top vent and it immediately turns off heat when that flame shows up, then as discussed before. It will do that 10 times until it kicks out the IF code.
 
Ok, I've replaced the flame sensor and I'm getting the same issue.

I did some reading on another post about a possible high limit issue. What do you guys think? Are the high limits built into the header? Any way to test them or would a visual inspection suffice?

Could the thermistor or auto bypass valve come in to play with an IF after 10 cycle attempts w/flame&heat?

Thanks as always guys
 
Do you have a copy of the circuit diagram? If so, you can verify the switches and all that with a simple meter. Just make sure the power is switched off to the heater.

Is the igniter being turned off once you see flame?
 
Hi pabeader, after those 30 seconds the green heat light turns off, is this how I know the igniter is turned off?

I checked the continuity on the blower and pressure switch and the igniter is clean and reads 15 on the multimeter.
 
What you see through the sight glass are the burners with the flames. So the unit is lighting up fine but won't stay lit. You seem to have replaced many parts and the only part left is the control panel where the keypad is.

An IF error is telling you that the system doesn't sense flame once the system lights up. None of the temp sensors will cause the IF error.
 

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