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OK. Also let me ask this, When blower starts is there any dancing or fluxuation in burner flame ?
Let me know if you have the dial type limit switch as shown below
Picture looks like lo nox burners that were installed in units in California and areas requiring them. I do not think they would effect the blower shutting off.
I am in Alabama and never actually seen them on a furnace and am not familiar with exactly how they work.Do they have wires attached ? D not see them on the wiring diagram
I do not think that is your issue personally.
I am suspecting there is an issue with the limit that controls the blower.Does the dial rotate as burners get hot and if so how far on dial are we getting before shutdown?
Ok from here it will get a bit more technical. The gas valve gets its signal from one of those relays. It sounds like the relay is cutting voltage to valve when it signals blower on.To start checking voltage , we need first to get correct wiring diagram. Look at link below and tell me which of the ignitions you have.
Lets ct goes off to see if we are losing the 24v out of control module and if limit is closed
I highlighted to wires from control to valve.Check between them. The limit wires are highlighted black. We should have 24v at limit as marked with black wires.
Sounds like a relay .My first suspicion would be the module..I would replace the 2 relays since they are inexpensive and you have already replaced the module.
Not sure these will solve the issue, but definitely seems we have a relay that is cutting out burners and as stated you have already replaced fan limit and module, so for the price, worth a shot.
Hopefully this will solve the issue.
Lets look at the pressure switch next.Silver canister on left with orange rubber hose going to it.
Disconnect hose from vent motor and leave attached to switch.Call for heat,and allow vent motor to start.Then suck on hose and keep a vaccum on hose until burners light and blower starts and see if burners will stay on as long as you are sucking n hose.
I will open to see if other experts have any ideas