Blower Fan stopped working/Coleman3120b751

[GD]

Hello, Need advice as to what should be checked /replaced for my coleman furnace model 3120B751 as the fan recently will not activate. Recently returned home late in the evening to smell the heat from the furnace coils which seem to function properly per the thermostat. However could hear a clicking sound from the relay/switch area with the fan not activating. Did try manually spinning the fan which did help it get going however it did stop again and not reactivate when the coils heated up. Also tried the continuous run mode at the furnace and t-stat switches with no response. Did check all connections (capped/at the connectors) as well.Possibly a relay? I did replace the sequencer back last fall. Any advice ASAP appreciated Thanks! Greg

[Robert]

Hi Greg,

With it running when you spun the wheel, common fault would be a bad run capacitor.


You would have to replace the run cap if the motor was going bad, so would replace it first and see if it takes care of it as it often does in these situations.


If you need ordering info, carefully remove the run cap without touching the terminals (can give powerful shock). Need the mfd or uf rating and the voltage rating.

Voltage will be 370 or 440.

Mfd will be in 7.5 to 10 range usually.


Thanks,
Robert

[GD]

Robert,
The MFD is 7.5 and the voltage 370 as per the wiring diagram just inside the control panel door area. Excuse me as I'm a little unfamilar as to the run cap location. I'm seeing the sequencer (left side) and wiring going to the upper connector (wiring to the motor and fan switch) along with wiring to the fuses and 4 terminals and 4 relays? At any rate, yes please direct me along with the required part/price.
Thanks again,Greg

[Robert]

Hi Greg,


It is mounted on motor side of blower housing. Small oval canister with two-four wires (usually) connected.


Run Capacitor # 1499 - 4461 can be seen and ordered from here by paging down :

http://www.aberdeenhomerepair.com/store ... B47%7D370V



Thanks,
Robert

[GD]

Robert,
Well upon close inspection and removal of the blower assy, I'm seeing only a grouping of four wires (red/blue/black/brown) which mate to their respective wires (wire nutted) that end at the main connector(molex?), These four wires appear to go directly to the backside of the blower motor with NO capacitor link (assy mounted or elsewhere). So, I'm wondering if the previous owner possibly retro fitted or whatever, the motor w/o a capacitor. Actually the red wire of the four is also just taped off and not connected. At any rate, Im not sure as to how I would fit the capacitor as It does have the spade/blade connections...Damn!..OK, three wires from the motor are linked to three wires back to the main connector via wire nuts. How do I determine which wires to which terminals on the capacitor if I go this route and looks like each wire would need to be fitted with a female end blade to affix to the cap, yes?
Hey thx again
Greg

[Robert]

Hi Greg,

Trace and see where those 3 wires go to and if/what they connect to after molex connector.

The red motor wire is the low speed wire and should be used for heat speed.

See if there is a model number of the blower assembly stamped on front of housing.


Do you have heat only or heat and a/c ?


You may have a shaded pole motor and no run cap needed for that.

In that case, IF motor is getting voltage , motor could be going bad.


Can you clean and read the sticker info on the motor ?

If so, give me that info.

For a run cap, it would have one or two brown and brown w/white stripe wires usually, but can have a few other colors.


May need an hvac tech or someone knowledgeable to help inspect and see what's up.


Thanks,
Robert

[GD]

Robert,
Those four wires look to come from inside the motor itself (disappear in between the brushes looks to be) They come out and cap off to larger gauge wires then to the main connector (plastic with approx 15 pin arrangement). The blower assy is clearly stamped NO# 3120A590 which is different from the info on the parts sticker on the furnace itself (it indicates two other blower numbers). The info stamp on the motor is clearly legible and it is an AO Smith 322P114 and says the following for the four wires Red=Lo,Blue=Med,Black=high and Purple=Line. Hope this info helps in identifying my motor type and symptoms. And yes, the furnace is Heat Only w/two speeds fan function wise. Let me knnow of any other info you may need...
Greg

[Robert]

Hi Greg,

The OEM motor is no longer available and no data for it, but it may not have had a run capacitor.

At this point, without me being there, best you can do is read entire motor sticker.


IF it needs/uses a run cap, it will be listed on that sticker what size. Also look at wiring diagram on motor and see if it shows a run cap and wires to it.

Otherwise, will need an hvac tech to diagnose actual problem and then may can DIY from there.



Thanks,
Robert

[Robert]

Missed last part of your last reply which shows no wires for a run cap. Check all wiring connections closely to ensure you get full power to motor.


For heat, you would use red or blue only. I would check for 120vac to ground from whichever it uses and also from the purple Line voltage wire.

Then make sure you have 240vac across them. Without a run cap (IF there is not one needed), then it is either getting 240vac or it is not.

IF it is, motor is bad or needs oiling if it has oil ports. IF not, then a wiring problem most likely.


Wire nuts and molex connector plugs are notorious for not making good contact.


Thanks,
Robert