Bryant Plus 90 398AAZ inducer motor

PCWilson

Bryant Plus 90 398AAZ inducer motor won't go on. Just replaced the Inducer Control board and the Fan Control Board. Fan Control Board LED flashing - this is the only diagnostic that this board gives - just means 24v at the secondary. Thermostat fine. Calls for heat. Relay engages. Wait, wait, no inducer motor. Based on reading here I will test for 120v at the leads on the Inducer control board. Any other suggestions?

OK, here's more of the story. Got up this yesterday morning, no heat. Went to the basement and I saw that the floor was wet - here and there but not a lot - on the side of the basement near the furnace. I didn't immediately put 2 and 2 together. We had a lot of rain last night and I though it might be related. Moved some wet boxes then decided to tackle the heater problem. After poking around a bit, I noticed that the plug for the pump that pumps out the condensate was hanging out of the socket and then it hit me that that was the source of the water on the floor. Pushed the plug in and it pumped out a tray-full of water. Now, I have to believe that these two events are related. How could that cause the inducer motor not to come on?

I took the drain hose from the inducer motor off and it dripped some water but not a lot. The other drain is clear plastic from the tray at the bottom of the chamber and I noticed that it had some drips of water clinging to the insides but really never noticed before if that's normal or not. I can't think of any other connection.

Anything else I should test for? If I power the inducer with 120v at that clip should it go on? Is there any safety switch - excessive moisture - that would prevent the inducer from going on?

Any help appreciated.

beenthere

Check for 120 to the inducer first.

PCWilson

Morning after. Got up and the heat was on. I didn't do anything, except plug in the condensate pump and put the doors back on. Wouldn't go on last night after the tray was pumped out but its back on today. Never got around to checking for 120v. I guess I should be happy (and I am) but also puzzled why it didn't go on before and does now. Is something else wrong? Should I check something else?

Any ideas appreciated.

While I was looking around here yesterday, I read that the inducer motor needs a periodic drop or 2 of oil. Is that true? Where do I oil?

Subcooled

Condensate pumps have a safety control (attached to a secondary float) wire to open the 24v circuit in the event it does not pump out to prevent the furnace and or ac from operating and keep filling it then flooding.

Usually if you have AC and heat the red wire will run through the safety. If heat only then white wire.

This sounds like your problem. Then find why pump did not work.

PCWilson

The upstairs heater has that float and shutoff in the tray but not the one in the basement. I wish it did, I wouldn't have had as much water on the floor as I did.

And the reason the plug came out slightly causing the pump to fail was no mystery - there was an extension cord running next to cord to the pump that became tangled with the cord when someone (probably me) pulled it from the other side of the basement.

Subcooled

If there are no error codes do you have an call for heat at the board? Jump out R & W at the board and see what happens.

PCWilson

As I mentioned in my 2nd post in this thread, everything's working fine now so I can't diagnose the problem anymore. I'm just preparing for the next time. I did jumper R & W when there was the problem but no difference.

Looking at the schematic, I see that there's nothing except a relay keeping power from the inducer motor and that relay is on a new board so I have to conclude that it's the inducer motor.

As beenthere suggested, I'm going to check for 120v on the edge connector powering the inducer motor next time to be sure but one of these times, it's not going to go back on.

Know if these motors need maintenance?

Subcooled

Actually the pressure switch is in the logic. If it is stuck open then the unit will sit dead, however you would have had an error code.

Good luck!

PCWilson

I wasn't sure whether the pressure switch is engaged as a result of the inducer motor going on (which made sense to me but I could be wrong) or the other way around. If you say it's in the logic then are you saying that the motor needs the switch to be on (or off)? How does that work?

Subcooled

The pressure switch is normally open. If at any start up the switch did not open from last cycle and is stuck closed then the logic in the board will not allow anything to happen. It will appear dead with a call for heat. (this depends on the model/year)

In normal mode the pressure switch is open. As the inducer operated and all drains, vents, etc are ok then the switch will close at a predetermined pressure.

I think in your case you may have the 3 wire switch on that AAZ, but full m# & S# would tell.

Also (depending on year) most AAZ'z had the separate ignition module which is gray or black box. They both have a 5 minute lockout, so if no pilot is established in 5 minutes then it locks out and furnace sits dead. Need to reset power for it to try again. The grey box has no pre-purge and the black has 8 second pre-purge.

So it's possible you were in lock out also, which is a whole different set of diagnosis method(s).

PCWilson

Great information. Thank you.

I see on the schematic that the pressure switch has 3 leads (orange, yellow and brown) and that orange is common and orange/yellow is the N.O. position. Next time it happens, I can see if orange/brown is connected to know if it sticks closed.

I see the ignition control pack on the schematic also. Haven't located it yet to see if grey or black but it's good to know that there may be a lockout mode. I suspect that it hasn't been a factor because I rarely reset the breaker and it has gone back on on its own. But will investigate further.

Again, thanks!