blower motor not working

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Dec 24, 2018 | 02:24 AM

bossecorvette

Thread Starter

Cruising

Joined: Dec 2018

Posts: 12

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blower motor not working

Corvette 74 - A/C - the blower motor is suddenly not working. Changed to a new blower switch - but no improvement. Have power to the new switch and the blower motor works with external power directly to the motor.

I am now planning to change the Master sw (2973407) and the Comp sw (2873872) - as per page 227 in the red Haynes owners workshop manual.

however, I just can not find these two switches? -

can anyone help help me to find them?

Do anyone know what the numbers as above mean? - are they GM partnumbers? or ?

Regards
Bo - Sweden

Dec 24, 2018 | 07:17 AM

Hammerhead Fred

Melting Slicks

Joined: Mar 2005

Posts: 2,095

Likes: 299

From: Midlothian VA

Quote:

Originally Posted by bossecorvette

First verify that your blower motor is grounded.
Run a jumper/temp ground wire from the block to the blower motor and see if it runs.

Dec 24, 2018 | 10:59 AM

henrikse

Pro

Joined: Nov 2016

Posts: 729

Likes: 118

From: Kelowna British Columbia

Quote:

Originally Posted by bossecorvette

The master switch and comp switch are mounted under the plate where your rotary heater controls are. Top right hand under

Dec 24, 2018 | 11:10 AM

Big2Bird

Le Mans Master

Joined: Dec 2006

Posts: 8,837

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Pull the resistor grid out of the duct and look at it.

Dec 24, 2018 | 03:42 PM

mrvette

Team Owner

Joined: Jul 1999

Posts: 65,492

Likes: 230

From: Orange Park Florida

Quote:

Originally Posted by Hammerhead Fred

First verify that your blower motor is grounded.
Run a jumper/temp ground wire from the block to the blower motor and see if it runs.

It is VERY common that a black ground wire from the blower goes to the + post on the starter, that is RONG you need it to be going to ground....in my '72, I ground it to the intake manifold , it happens VERY often when someone changes the starter motor, the wire sometimes goes under that starter bolt, and maybe a factory did it on the bellhousing.....but I keep it simple.....intake manifold.....on my car it also grounds the wiper motor....so maybe check that too, just for grins....

Dec 24, 2018 | 05:50 PM

Peterbuilt

Le Mans Master

Joined: Aug 2006

Posts: 7,426

Likes: 1,559

From: mount holly NC

2025 c3 ('74-'82) of the Year Finalist - Unmodified

2019 C3 of Year Finalist (appearance mods)

Testing by the numbers.

BROWN #50 is LOW speed.
When your switch in the heater control is on LOW speed this wire will have 12 volts.

TAN # 63:
With the switch in the next click, the tan wire will have 12 volts on it.

LIGHT BLUE # 72:
On the next click, this wire has 12 volts on it.

All LOW speeds go through the resistor.

ORANGE has a separate fuse and bypasses the resistor.
Gets 12 volts only on HIGH.