What's the bypass technique to check to see if my blower motor in the attic is blown out??

Question

The outside unit is coming on, but the fan upstairs is not.

Answer 1

since the outside unit is coming on you know there is power going to the unit in the attic because this unit controls the whole system....if the fan motor will not come on there is only three possible problems...1 bad motor..2 bad capacitor 3 bad fan relay or electronic board that controls fan motor....there is no safe bypass technique to check fan motor...but you can trace the black lead going to the fan motor and hook it directly to the power as the common wire(white or yellow) always connects to the power...be sure and turn the power off before attempting to work on the unit

Answer 2

Got a volt/ohm meter handy?

The first thing you need to check is the voltage, which should read somewhere between 125 volts and 115 volts. 125 is a little high but power companies sometimes set the transformers high to accommodate for multiple housing. Set the unit so that the blower motor should be energized. If you have power at the receptacle, check motor with the ohm meter to see if the windings are open by placing the meter leads on each side of the plug end (people confuse this term with a household receptacle) or cord end. Depending on the motor, you should get a reading of 20 ohms or less. If you get a reading of OL (open line) the windings are bad. Some motors have a start switch or centrifugal switch; therefore, the above test will show only show the start windings are good. But the motor will run slowy on the start windings, which indicates the start switch or the run windings are bad.

You should also check each prong of the plug end to the motor base to see if the motor wiring's are shorted to the motor frame. It should be tripping the circuit breaker if it is shorted. If everything checks okay, you could have a loose connection that break the circuit when motor is energized.

As far as those jumper wires goes, if you don't fully understand what you're doing, you are going to end up with a face full of hot molten...

Most units have a schematics on the door of the unit that are fairly easy to understand.

Answer 3

this is if you have an AC motor (it will say on it)
and if the motor is hooked up to a circuit board.
If you know nothing about electricity.. call an HVAC guy lol


1. locate the 3 wires (red,white,black) going from your motor to the circuit board.

2. disconnect the 3 wires.

3. find an old extension cord and cut one end off so you just have the plug, and 2 bare wires. (or an old radio.. anything.. just need a plug!)

4. (DONT PLUG IT IN YET LOL) tie one of the wires to the black motor wire, tape it up. tie the other wire to the white motor wire, tape it up.

5. plug in! It now should be bypassed and working, (unless the motor is bad!)

6. if its spinning the wrong way.. you can switch the wires..

good luck!

Answer 4

First answer correct. Volt Meter can do a lot in a house as electricity is fairly simple. You either have voltage or not. If, you have voltage to the motor it should run, if not it bad. Also try being careful and spin the squirrel cage by hand to see if it go. If, the fan run when you manually spin it, it may be the "Starter Capacitor" on the fan. This too can be check with you Volt meter set to OHM setting. First disconnect the power of turn off your breaker, test with meter to be sure the electric is off. Take a Screwdriver and short across the posts on the capacitor to drain any stored volts.
Easy way now is go here if the link work;
assets.fluke.com/appnotes/automotive/beatbook.pdf
Dang, it a PDF file and I can not get the link to work.
On OHMs you connect across capacitor and should see a slow rise to infinity. Best I can explain.
But, usually spinning the fan and it going is a sign the capacitor is bad and easy to do.

Answer 5

remove the black wire going to the motor and the white wire going to the motor, (common and high speed) with a multi meter attach one probe to the black and one to the white if the meter shows a reading the motor is good. If there is no reading the motor is bad. If it is a 115 volt motor, and yoou can wire it direct to a 115 volt source (safely) this is a sure fire metheod of determining if it is good. If the motor shows to be good, then you either have a bad fan relay, a bad control board or a bad capacitor.

Answer 6

You can open the unit in the attic and use a jumper wire from the red terminal (R) to the green terminal (G) and the blower should come on.

If it does you will have isolated if it is the stat or circuit board in the unit.

If if does not come on then you will have isolated that the blower itself is faulty or does not have power going to it. You can remove the blower fairly easy and check it with power if your abilities allow.

I do except email. (see profile)

Answer 7

Check your fuse (circuit breaker), then some motors have circuit breakers in the connection box. Check voltage to the connection box. If you have voltage see if you can switch the outside units electrical with the upstairs unit. It would help you out to get a cheap volt meter to have around the house for *HIT like this.

Answer 8

Can You Bypass A Capacitor

Answer 9

GO TO THE THERMOSTAT
PUT TO THE OFF MODE AND TURN ON THE FAN TO ON NOT AUTO. THE FAN SHOULD COME ON. IF NOT CALL A HVAC COMPANY