Ask Me Help Desk - Bryant furnace won't start, error 42

Hi all,

I have a Bryant furnace, Plus 90i Evolution (355AAV060100) that won't start and gives error code 42 (checked by flashes and on service section on Infinity thermostat). The unit is mounted vertically in the basement, age unknown but thought to be only a couple of years. Was running fine until yesterday morning.

From the error code I gather its inducer not starting. The blower comes on as expected but inducer doesn't start. I've checked the inlet and outlet pipes which appear free from obstructions. The spindle of the inducer turns freely by hand. Wiring block to the inducer and connections appear fully seated.

Any suggestions much appreciated,

Mark

Check to see if the inducer is getting power during the start cycle. Hook up your meter then activate the unit in the heat mode and watch for the inducer blower voltage signal. No voltage signal is possible bad board if you get a voltage signal then it is possible a bad inducer motor.

Thank you for your quick reply.

I'm not sure what the wiring scheme is for the motor. On the inducer wire harness/connector block I have 6 wires; white, black, yellow, orange, brown and green/yellow. Could you advise where I should see the signal and what range to expect please on initial start up?

Thank you very much,

Mark

Quote:

Originally Posted by hvac1000

Check to see if the inducer is getting power during the start cycle. Hook up your meter then activate the unit in the heat mode and watch for the inducer blower voltage signal. No voltage signal is possible bad board if you get a voltage signal then it is possible a bad inducer motor.

I looked for a wiring diagram to post for you but I cannot locate one for your model number yet.

Hi,

Thank you for looking for that. I removed the rear plastic cover from the inducer motor and there's obvious signs of a burnt out part. It looks like a fried transistor. I've attached a pic, it's the second one down on the right side of the board.

So my next question is, how do I remove the inducer motor? I have another furnace that heats the basement with a similar motor. So my plan is to swap them out if it's relatively easy until I can get a replacement motor. The second pic shows the inducer from the side with the mounting points. I've undone the three anti-vibration mounts so the inducer is now free from the carrier. I'm not sure how to removed? Do I have to remove the larger platic panel for the chamber behind to get to the fan and remove that in order to extract the inducer spindle or is there an easier way?

Many thanks in advance,

Mark

Quote:

Originally Posted by hvac1000

I looked for a wiring diagram to post for you but I cannot locate one for your model number yet.

DEALER SERVICE BULLETIN
Number: DSB 08-0003 Date: 2/18/08 Supersedes: New
Variable Speed Inducer Kits
PRODUCT CATEGORY:
Residential Furnaces
MODELS AFFECTED:
Bryant 355CAV 355AAV 355MAV 355BAV
Carrier 58MVC 58MVB 58MVP 58UVB
Serial Number(s): ALL
SITUATION:
The service inducer kit used on the new Step Modulating Furnace (355CAV and 58MVC models) has
a part number that is different from the service inducer kit used on other variable speed furnace
models.
The difference between the Step Modulating inducer kit and the kit for other variable speed furnaces
is the Step Modulating inducer kit includes the Downflow Spacer Kit, KGACC0101SPC in the kit. The
instructions in the new kit have been revised to show how to install the spacers for furnaces installed
in the downflow position.
These 2 upgrades to the components in the kit require a new part number to reflect the correct
components to be included in the kit.
There are no other operational or construction differences between the inducer assemblies in either
kit.
SOLUTION:
The existing inducer kit, 320727-755 can be used as a service replacement for all furnaces including
the Step Modulating furnaces until exhausted. It is recommended that furnaces installed in the
downflow position have the Inducer Spacer Kit (ordered separately from Finished Goods) installed on
the motor grommets when using the 320727-755 kit. The inducer spacer kits are available in bulk
quantities of 25 individual kits, using kit number KGACC0125SPC.
The latest inducer kit, 324906-762 is backward compatible to all models shown in the table above.
This kit includes the Downflow Spacers.
Table 1 below lists all the parts that make up a service inducer kit.

DSB 08-0003 2
Table 1
Differences between ECM Inducer Kits
Previous Inducer Kit Latest Inducer Kit
320727-755 324906-762
Part number Part name Part number Part name
324906-704 Inducer Assy, Variable 324906-704 Inducer Assy, Variable
IIK320727-1
Instructions, Ind Motor
Kit IIK324906-001
Instructions, Ind Motor
Kit
321078-302 Carton 321078-302 Carton
320614-101 Label, shipping 320614-101 Label, shipping
325875-401 Pad, carton 325875-401 Pad, carton
34411B71 Staple 34411B71 Staple
KGACC0101SPC Inducer Spacer Kit
The instructions for the latest inducer kit, 324906-704 are attached to this bulletin.
Warning: Do not perform any of the servicing instructions provided in this Service Bulletin unless you are a trained and qualified
technician. Observe all precautions in the instructions, equipment tags, labels, and observe all other safety precautions that may apply.
Failure to follow this warning could result in property damage, personal injury or death.

As you can see there have been some changes to the inducer assemblys so MAKE DAGGONE SURE you buy the correct one. Unless you like to spend money I would not take a good operating furnace and steal parts from it to use on another furnace since it is possible to create more problems that way but that decision is up to you. Good Luck. All items here listed for you out of the Factory service notes for 2009.

Hi,

Thank you for your help and insight. From the service bulletin it looks like it's specific to downflow furnaces, fortunately mine is upflow. The docs that you sent with the instructions are great, thank you very much.

I think you're right, by poaching parts from one unit to use on the other I open myself up to a host of potential other problems.

I checked the unit again, the date of manufacture is Aug 2006. I'm going to try to contact Bryant on Monday to see if I can get a replacement under warranty, after all they advertise a 5 year warranty on hardware. But, I'm not overly optimistic.

Thank you again for your advice, I really appreciate you taking the time to reply. I'll give an update once it's all running again.

Regards,

Mark

Quote:

Originally Posted by hvac1000

As you can see there have been some changes to the inducer assemblys so MAKE DAGGONE SURE you buy the correct one. Unless you like to spend money I would not take a good operating furnace and steal parts from it to use on another furnace since it is possible to create more problems that way but that decision is up to you. Good Luck. All items here listed for you out of the Factory service notes for 2009.