Is blower motor supposed to be off when off?

[BigPoser]

When I have my slider switch in the off position, my blower motor still runs in the lowest setting. Is it supposed to do this, or should it actually be off?

Also, I have a 4 speed options for the blower, and only 3 work. "Hi" doesn't work at all. Any thoughts as to why the other 3 speeds work, but not the 4th?

Thanks in advance.

Brandon

 

[kdo58]

yes it suppose to stay on

 

[bucket]

Yeah, the 70's A/C trucks have the blower on all the time. There is a relay mounted near the blower motor that triggers high speed.

 

[chengny]

2 X what David says. The blower circuit is designed to always run the fan. Even with an A/C equipped system, moving the mode control arm to OFF only blocks most of the air from entering the cab through the vents:

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Also, I have a 4 speed options for the blower, and only 3 work. "Hi" doesn't work at all. Any thoughts as to why the other 3 speeds work, but not the 4th?

I have a thought why. The most common cause of one (or more) blower speeds being unavailable is a failed coil(s) in the blower motor resistor stack.

 

[87scotty]

Occasionally a melted plug but yea somthins burnt up

 

[bucket]

I have a thought why. The most common cause of one (or more) blower speeds being unavailable is a failed coil(s) in the blower motor resistor stack.

IIRC, high speed doesn't pass through the resistor. The resistor is there to slow down the blower for the different speeds, you don't want the blower slowing down to get high speed. High speed gets direct ignition 12v through the high speed blower relay.

 

[chengny]

IIRC, high speed doesn't pass through the resistor. The resistor is there to slow down the blower for the different speeds, you don't want the blower slowing down to get high speed. High speed gets direct ignition 12v through the high speed blower relay.

Yep, you recall correctly. The correct answer was...faulty relay - not resistor. That's what happens when you rush when answering a question. Mea Culpa.

Below is the diagnostic chart for a "Blower Inoperative In High Speed Only" - 1973 C/K with Four Seasons Climate Control:

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[BigPoser]

Gentleman,

Thank you very much. I love this frickin site!