need help with your rtu

[buzz1234]

it will run fine when i am there i run thru 5 or 6 cycles with no problem a couple of hours lator i will get called back blowing cold air ignition failure

[hvac wiz 79]

Check connection at gas valve. Those plugs get loose connections to the point it can be a nuisance indeed and replacing it is the fix. I've had quite a few. Just an idea, which I don't typically offer ideas or instances I've had but since you already replaced a lot of parts . . Just a thought. I'm not a predator fan because they have in what my opinion is minor design issues that effect heating.

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[drunkenkoala]

Explain more, I am very familiar with gas issues please explain more, what are you seeing, gas pressures? temp rise? etc...

[valdelocc]

My guess is that the primary limit is tripping after the burners fired for awhile, you are getting flash code 9, right? strap a thermometer to the limit, see if it gets near 190F.

[gravity]

check resistance thru rollout switch and hall switch. could be one problem.

also check for wind. these units hate wind.

and lastly, check pilot flame

[brian.cornell]

If you are getting a flash code 9 ignition failure code that can also be an open primary limit check for airflow issues/dirty filters/dirty coil

[EEAllen]

okay, make sure you are looking at the right PCB, there's one at the burner assembly, if that work has a steady blink, then it's working fine, according to what you say, it might not be ignition failure. Check the main PCB, the place where all the wires are at, see if you get a 9 flash code at the Heat Delay LED, if it does show 9, that means one of the limit is tripped. Now go to the burner compartment, there's a high limit that sticks into the burner, see if that's continuity, most likely it's that place that shows error. And yes, if you restart the power supply, the unit will run fine again for some time. If it does run fine, that means you're not getting enough return air, check the return duct filter etc...