redmachodevil

A/C Question: Just replaced Fan Control Unit and now the Blower false starts every time the Cooling goes on

I had an HH84AA009 in my carrier air handler. This air handler does both cooling and heating. A few days ago, the blower stopped turning off and remained constantly in the "on" position (even after moving the switches on the thermostat to "off" and Auto)

When I'd power off my system and open the unit, If I tapped the relay with a screw driver the fan would turnitself off, however once it went on again it wouldn't turn off.


I replaced the unit with a new ICM275. I replaced wire for wire one at a time, so I am pretty sure that I did it correctly.

Now, the fan works well, however when you put the unit into cooling mode, the blower will go on, and then as soon as the cooling kicks in, the unit kind of "resets" the blower turns off and then tries many consecutive "false starts"


Have I done anything wrong?

Is this newer controler board (with new kind of relays) different and therefore I need to change the wire connections


The new replacement board is different than the original one. The old one has the big old style relays while the new one has the newer relays. This new Board (ICM275) is the currently availible replacement for many legacy Carrier boards including the HH84AA009 (which is the one I had). The board has the same form factor and all of the connection terminals are labeled exactly the same as in the old board. As mentioned before, I connected the wires from the old to the new one at a time to make sure I got them right.....

There is a delay feature that can be adjusted by moving a potentiometer dial.

Maybe somewhere out there knows if these newer boards (that use SPST-NO blower relay, SPDT blower speed relay and SPST-NO relay for humidifier) require any wiring changes from the old boards (that use SPST-NC or DPST-NC heating fan relay and DPDT cooling fan relay 2f)

THe board is made by ICM controls and the schematics are on the icm site.

UPDATE!, it seems that when I set the blower settings at the stat to "on" instead of "auto" both the cooling and blower work. When I change the setting to auto, I get the problems.


this is a link to what the old board looks like:


this is a link to how the new one is wired:

papasru

i am about to purchase and replace my HH84aa009 with the ICM 275..what did you find out about the blower motor glitch on cooling

qbert

Try disconnecting low voltage wiring. Jump out r to g see if it still does it, If it does not, inspect wiring for nicked conductors in the low voltage wire

mikef54

Does the new board have a Carrier part # on it? If not I would contact Carrier and be sure it is an exact replacement board. The chips on those boards tell the unit how to operate. Manufacturers often have different contractors program their boards to operate the unit the way they want. May not be what your problem is,but I would check to be sure.