[coldathome]

I have a Bryant CAV395024070 furnace that's taking a code 31. When I run a component test, the inducer motor comes on, sometimes for only a second, sometimes for the proper amount of time, sometimes not at all. The remainder of the components all go through the test no matter what the inducer motor does. When I turn the thermostat on, sometimes the furnace runs, other times only the blower motor comes on and will run until I either turn the thermostat off or lower the set temperature so that the thermostat is satisfied. If I get the furnace to run and it satisfies the thermostat and shuts down, it may come back on as normal the next time the thermostat calls for heat. Other times the inducer motor will start then stop before the igniter glows and you can hear a noise coming from the control board. When this happens I reset the manual reset limit switch (flame rollout switch) and the noise goes away and the furnace will then run as normal. Is the problem with a relay on the ctl. Board?

For code 31 it is... Pressure, Draft Safeguard, or Auxiliary limit (when used) switch did not close or reopened. If open longer than 5 minutes, inducer shuts off for 15 minutes before retry. Check for: ***Proper vent sizing and condensate pitch ***Vent restriction or high winds ***Defective inducer motor or start capacitor ***Defective pressure switch or connections. If it opens after trial for ignition period, blower will come on for 90 second recycle delay. ***Inadequate combustion air supply ***Low inducer voltage ***Disconnected or obstructed pressure tubing The pressure switch has been replaced, I have checked the venting and condensate pitch. It is a new filter and has adequate combustion air supply.

[letmetellu]

The inducer motor is a very low powered motor and it takes only a slight tightness to not let the motor run as fast as it need to to make the switch engage.
So turn the little black wheel with you finger just a little spin and it should turn with out any obstuction, even the draft of the wind will make them turn.
I am just telling you this because it could be what is not completing the cycle.

Run the test again and be sure aand pay attention to what does not work when it should, (the gas valve will not open during this test).

[KC13]

If you are resetting a flame rollout switch repeatedly, aren't you getting curious about why? Flame rollout... flame rollout... FLAME ROLLOUT... doesn't that sound kind of bad? It is! Flame rollout occurs when the burner flames are straying away from their intended target area, and is usually the result of a leaking heat exchanger. Try this: observe operation from start-up. Do you notice disturbance of the flames when the main blower starts? If so, have the unit inspected by a pro. Model 395 with automatic ignition carries a 20 year heat exchanger warranty.

[coldathome]

I have ohm'd the flame rollout switch out and it is good. I took the switch in to a local service shop and they said they would sell me a new one but that the switch tested good when they ohm'd it out. Also there is no disturbance of the flame when it is running, I have observed it. The inducer motor spins freely.

I had to have a repairman replace the 24 volt transformer and the pressure switch. I think that whatever caused the transformer to fry must have damaged something on the board (a relay?). Is there a relay that controls the inducer motor? I would suspect that since it seems that the furnace operates properly as long as the inducer motor starts up as it should. The only time I have to reset the flame rollout switch is if the inducer motor starts then stops before the igniter lights up or the gas valve opens and there is a noise coming from the control board. This will interrupt the circuit and sometimes cause the inducer motor to start when the reset is released. The furnace will then run for a few cycles most of the time.

Is there any way to test the relays on the board to confirm this? Also, if the relay was bad/flaky could it possibly cause the thermostat to think the furnace actually fired and cause the blower to continuously run since the thermostat is never satisfied? Maybe the board isn't detecting a failure when one has actually occurred?

[coldathome]

Just an FYI/Update: It appears that the control board is definitely the issue. In trying to get the furnace going again I tried to run the component test again, the inducer motor was either not coming on or would only come on for a second or two so I was making sure the connection for the inducer motor on the control board was secure. When I pushed on the connection, the inducer motor started running. I disconnected the leads from the control board and made sure the connectors did not get pushed out or have damage to them. Did not see a problem so I plugged it back in and ran the component test again. The inducer motor ran for a second or two and stopped, so I rapped on the plastic cover for the control board and it started running and successfully completed the component test. I then reconnected the thermostat and tried to fire the furnace up. Once again the inducer motor stopped after about a second so I rapped on the control board again and the inducer motor took off and I now have heat.

I found the control board on the internet for $109 compared to $280 everywhere else. The new control board should be here tomorrow. We have been without a furnace for 2 winters. It will be so nice to not have to get propane or depend on ceramic heaters. It sucks being poor.

Hopefully documenting my problem will help someone in the future.

I'll keep you posted on what happens with the new control board.

[KC13]

Good job! The square multi-connector receptacle is prone to failure of the solder joints on the back of the board, and the action you took resulted in a momentary restoration of the circuit(s) affected. $109 is a good price for that part.

[MarkwithaK]

Wow, 2 winters without heat. That sucks but glad you got it solved.A little internet searching led you here and now you fixed your own furnace, congrats! Just goes to show you the power of shared knowledge.

[coldathome]

Received the new control board. Installed it per the instructions and I have heat. Beautiful!

Now all I have to do is figure out how to wire in my heat pump unit properly. We had the house built but the installers did not have the units wired properly to use the heat pump for heat in milder temps.

The house was built in 1995 so I have no recourse with the installers.

[KC13]

Ideally, you should install a dual-fuel thermostat to optimize control of the system. If installed and configured correctly, it will provide automatic switching between heat sources for most economical operation. This is no simple task, and would best be left to a pro. Don't feel bad about going that route - you saved some cha-ching doing the circuit board yourself.

[navibern]

Coldathome, I have the same problem with the same furnace, now I need to buy a control board, do you remember where on line you bought this contol board, thanks. [email protected]