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AC/Heater Blower Motor

Started by john108, September 26, 2016, 11:36:46 PM

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john108

1968 Dodge Charger.
I will start with what I think I know.  Please Correct me where I am wrong and please fill in the unknowns.
I believe my fan switch provides 2 speeds plus off.  It has 3 wires.
Some wires go to the board on the heater box that has coils of wire.
I believe that somehow that controls the current or voltage to the blower motor.

The blower motor has a two wires, one being a ground.
I would like to test the motor before installing it.
My power supply can only handle up to 5 amps, maybe.

What current will the motor draw and any suggestions on how to test it.
Thank you
John


Nacho-RT74

12 volts. I have never checked the load with an ammeter but the car one. Since is not scaled, I would say it must draw around 5 and 10 amps between speeds maybe even more, up to 15~18 amps at max speed. It is the device on car what sucks more power of all.

Blower switch provides two speeds, but low speed is by default and doesn't go through the lever fan switch, but just like an input to feed the fan speed when you select mid and high every one to feed the resistor block. Then you got all 3 speeds. Off is a direct control unit switch, is not on the fan lever switch on AC cars.

Dunno on 2nd gens but 3rd gens got a 4th low speed selecting deff and heater, and is fixed. You can't change it.

Test it to the battery.
Venezuelan RT 74 400 4bbl, 727, 8.75 3.23 open. Now stroked with 440 crank and 3.55 SG. Here is the History and how is actually: http://www.dodgecharger.com/forum/index.php/topic,7603.0/all.html
http://www.dodgecharger.com/forum/index.php/topic,25060.0.html

Nacho-RT74

Well I have talked from the 3rd gen point of view of the system. I can be wrong on 2nd gens, but pretty sure they work the same, maybe wired a bit diff though due the diff setup of the control unit assembly.

EDITED... just confirmed by diagrams and yes, 2nd and 3rd gens blower system seems to work exactly the same.

when you turn on the AC, the blower source is spliced, one to the lever switch, like an input source to it and the other one to the resistor block feeding directly the blower at low speed through the respectivelly resistor. While this happens, fan lever switch is set at low speed but internally this power is going nowhere, like it was on OFF position. The control switch is already doing that speed.

when you set mid and high speed on fan lever switch, the control unit keeps feeding low speed resistor and fan lever switch at the same time, but on mid or on high position, the power is going now through the lever switch to the mid or high resistor accordingly. By ohms law the blower will take the most power available, which of course will be mid or high speed resistor source according to the speed you selected, no matter if low speed is still being feeded from control unit source.
Venezuelan RT 74 400 4bbl, 727, 8.75 3.23 open. Now stroked with 440 crank and 3.55 SG. Here is the History and how is actually: http://www.dodgecharger.com/forum/index.php/topic,7603.0/all.html
http://www.dodgecharger.com/forum/index.php/topic,25060.0.html

john108

Thank you Nacho
More complicated than I have a right to know.
I think you are telling me to test it with a 12v car battery and not my power supply.
You don't think that a Car Battery will put too much current through the fan motor.
The motor is not installed and doesn't have the benefit of the resistor block??

Can I power the motor with a battery charger.  Would the 6 volt setting burn it out, as a test?
I know AC motors don't like long extension cords.  
I can use a battery, or the battery charger set to 6 or 12 volts.

john108


BLK 68 R/T

Just use your car battery, it is a 12v motor.

Quote from: john108 on September 27, 2016, 02:32:52 PM
I know AC motors don't like long extension cords. Do you mean AC as in air conditioning motor, or AC as in alternating current? there are no alternating current motors in cars, everything is DC current 

Nacho-RT74

Just to test the motor is enough source it from from the car batt. On high speed the power doesn't go through resistor block.

About the rest, I just wanted to explain why the fan blower speed switch got three positions instead 4. And 5 amps is really not enough load for the blower
Venezuelan RT 74 400 4bbl, 727, 8.75 3.23 open. Now stroked with 440 crank and 3.55 SG. Here is the History and how is actually: http://www.dodgecharger.com/forum/index.php/topic,7603.0/all.html
http://www.dodgecharger.com/forum/index.php/topic,25060.0.html

john108


john108

I powered it with a 12v car battery and it looked and sounded like new.
It really spun smooth and fast.
Thank You