Is leakage of AC voltage through blower relay normal?

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Tom O.

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Hi all,
I have a Comfortair Patriot oil furnace, very simple system.
This year at 5 years to the month since I got it the blower motor blew out when I fired it up for the first time since May. (motor actually caught fire)
I bought a new motor and capacitor (exact oem, 4 speed)
There is no PCB controller, there is a SPST time delay relay that is for when the furnace is running. (blue wire)
There is a DPDT relay for turning on the blower, and when actuated cuts the power to the blue wire & activates the black wire.
Supply 120v ac voltage is supplied directly from the main junction box.
Solenoids are 24v

At idle, I show 4-6 volts AC between common and blue or black, without the motor connected.
With the air cond turned on I get 120v on the black lead and 12v AC on the blue.
With heat turned on, I get 120v on the blue lead, and about 6v AC on the black.
Motor is not connected on any test.
Is this leakage normal?
I always thought it should read zero, and I know applying voltage to more than one tap on a multi speed motor is bad.
I don't want to fry my brand new motor.
Thanks
Tom

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Fitter30

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Any time and any speed the motor is powered the other leads have power on them by electromotive force. Thats one reason the other leads are capped off or when two speeds are used its on a open contact.
 

Tom O.

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Any time and any speed the motor is powered the other leads have power on them by electromotive force. Thats one reason the other leads are capped off or when two speeds are used its on a open contact.
It's the leads from the relay without the motor attached. The relay is "normally open" on the black high speed A/C lead and "normally closed" on the blue heat lead. When energised the relay is closed on the black, open on the blue. I am showing 12VAC on the blue open circuit in the energized position. Even more odd is I when the relay is active I get 4VAC on pin 4 of the relay and 12VAC on pin 5 of the relay. I don't know if this is because of any overload circuitry in the relay or some type of short between pin 5 and 3. The sole purpose of that relay is to make it impossible for power to be supplied to two leads at the same time.
 

wwhitney

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If you are taking the readings with a standard high impedance meter, they may reflect "phantom voltage". Try a low impedance meter, or put a safe small load across the leads (40W light bulb?) and then measure the voltage across the load.

Cheers, Wayne
 

TonyH

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If you are taking the readings with a standard high impedance meter, they may reflect "phantom voltage". Try a low impedance meter, or put a safe small load across the leads (40W light bulb?) and then measure the voltage across the load.

Cheers, Wayne
Digital meters vs. Analog meter. I always use analog meter on house wiring work.(Good old Simpson and Amprbe)
 

WorthFlorida

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Digital meters vs. Analog meter. I always use analog meter on house wiring work.(Good old Simpson)
The great old Simpson 260's were 20,000 ohm's per DC volt, 5,000 Ohm per AC volt, written right on the face of the meter.
 
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