A/C Fan stopped working on the Hi setting

HUGHP · 09-13-2011, 12:59 PM

We have just one Coleman Mach rooftop A/C and until this past weekend the fan performed perfectly. Now only blows on the low setting whether on air or furnace. Swapped out the thermostat with the same results. The green wire looks fine(to me anyway

). What should I check next to get the fan/blower back to operating on the Hi setting please? Where is fan/blower located?

Dave78Chief · 09-13-2011, 08:39 PM

Coleman ACs are designed with a upper unit assembly (roof top) and lower air distribution assembly (inside ceiling). You typically need to know what the model number of each is so you can locate the proper service manual. You may have been provided the operator documentation for each. If not, you have to pull the covers off to fine the information. Once you know that you can most likely download the service documentation from Airxcel | RV Products Tech Info

There is a relay board in the ceiling unit that has relays on it. The 12VDC signal from the thermostat controls the relays which in turn contol the 115VAC power to the fan motor. The are different boards so you have to know what configuration you have.

Dave

wa8yxm · 09-14-2011, 10:59 AM

Possible issues: Control board (including relay) failure.. Motor Failure.

That about sums it up.. The motor connects to the control board with "Number of speeds plus 1 or 2 wires" The 2nd plus wire however does not go to the control board.

On the motor may be a connection diagram. ON my Carriers it is on the cover of the junction box

Fing out the COMMON (often white) wire and hook one lead of an AC-Voltmeter to it (Multi meter set on 200 or more volts AC)

Find the LOW and HI leads hook the other lead to the HI.. You may use a straight pin to pierce the insulation (DO THIS WITH POWER OFF)

Now have your "Ground crew" turn it on hi and check for voltage.. If there is none. it's the control board or relay, if it's there, it's the motor. .That simple.