Blower motor issues
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4wd High
Joined: Feb 2013
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Blower motor issues
99 Super Duty 7.3, 312,000 miles
My blower motor still has only two speeds of four: medium and high. I have replaced the blower motor, speed resistor on condenser box, all three switches on control panel. No resolution yet.
Anybody know where the problem lies?
My blower motor still has only two speeds of four: medium and high. I have replaced the blower motor, speed resistor on condenser box, all three switches on control panel. No resolution yet.
Anybody know where the problem lies?
Hotshot
Joined: Jan 2004
Posts: 19,767
Likes: 1,082
From: St Louis
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4wd High
Joined: Feb 2013
Posts: 9
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Back on this Blower Motor issue
The relay receptacle has power on the same terminal on fan speed 1-3 switch positions. Looking at the picture posted here, it is the top left terminal each time. On speed position 4 (high) there is no power to the relay.
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Hotshot
Joined: Jan 2004
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From: St Louis
That isn't a relay that is pictured above, it's the resistor.
Were you measuring with the resistor plugged in or not? What were the actual voltage readings? You should measure from zero in HIGH with the voltage rising at that pin with each step of the switch to a lower speed.
That is the pin that goes to the "low" side of the blower motor.
Expected.
To note, power isn't coming out of the blower resistor to run the motor, it's the opposite. The "high" side of the motor has switched battery voltage on it all the time that the system is turned on. The resistor is in the "low" or ground side of the motor circuit. The fan speed switch bypasses some or all of the current through the motor to ground thus regulating its speed by limiting the current through the motor.
has power on the same terminal on fan speed 1-3 switch positions
it is the top left terminal each time.
On speed position 4 (high) there is no power to the relay.
To note, power isn't coming out of the blower resistor to run the motor, it's the opposite. The "high" side of the motor has switched battery voltage on it all the time that the system is turned on. The resistor is in the "low" or ground side of the motor circuit. The fan speed switch bypasses some or all of the current through the motor to ground thus regulating its speed by limiting the current through the motor.
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Hotshot
Joined: Jan 2004
Posts: 19,767
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From: St Louis
Hotshot
Joined: Jan 2004
Posts: 19,767
Likes: 1,082
From: St Louis
That was the OP, not the guy that just necro'd the old thread. Maybe he has the same thing as the OP but it's questionable. Until it's definite, not going to go through the work of pulling up a diagram based on guessing.
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From: Billings, Montana
You’re right, my bad.
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