I am replacing my old burnt 18k201 circuit board with the new 31m73 on my Lennox air handler and have run into a problem with the wiring. The exiting wiring harness is a 14 pin P2 connector and the new one has a 10 pin J85. Is there an adapter available to mate the 2 or at least some intructions on the pin assignments in each connector? Also the old board had a ground wire that connected to the air handler cabinet. I do not see a place to reconnect this to the new board. Does it not require grounding or am I missing something?

Are you sure you have the correct board? Usually all replacement boards come with any adapters that would be needed and almost all of the time no adapter is needed.

According to this the board you have is not a replacement for your old board.

31M73 -- LB-101124 CONTROL BOARD KIT
Replaces 18J78, 18J7801, 32M18, 32M1801 Only

Several online parts distributors as well as my local ac parts store all listed the 31M73 as the direct replacement for the 18K8201 (my mistake not the 18K201 as mentioned in my original post). But it sure doesn't seem so direct to me. I would like to know where you got your information though as it may prove useful if I have to return the 31M73.

The new harness that comes with the 31M73 is the problem. Obviously it plugs into the new control unit, but there is no place to plug in the other end. As I understand it this harness is designed to connect to a relay sequencer board. My air handler does not have a relay sequencer board. What I need to figure out is a way to marry the female 14 pin P2 connector that I unplugged from old burnt 18K8201 circuit board to the 10 pin J85 connector at the end of the new harness. I am guessing that I need either a different harness or to remove both connectors and start splicing, but I would like some dirction on what connects to what.


Thanks for your help.

As I understand it this harness is designed to connect to a relay sequencer board. My air handler does not have a relay sequencer board.

OK install the relay sequencer board.
My source was in some books I have. The info might be old BUT if your board connectors do not match the new board connectors and there is no wiring adapter something is wrong with that picture.