AC Blower speed

7173Mustangs.com

Help Support 7173Mustangs.com:

Joined
Sep 2, 2012
Messages
1,523
Reaction score
114
Location
Blue Springs, MO
My Car
1971 Mach 1, Grabber Blue w/Argent stripes. Original 2V 351C Auto, Tilt, rear defog, Black Comfortweave Interior. Under restoration. Original colors, 4V 351C, 4-Speed, Spoilers, Magnums, Ram Air. All Ford parts.
OK, last year I replaced the blower motor in my heater box with a new 4 Seasons blower motor. The original had a squealing bearing, so I went with new.

Now when I run the fan in the car, it feels like it has about me 50% of the speed the original had. It is quiet, but the air speed out the vents just seems lower.

Has anyone else experienced this? Is it possibly in the fan switch on the dash? Are there electrical values I can test? Did Ford use an in line resistor on the blower that 4 Seasons has on the fan motor too?

It’s definitely AC season, so your advice is appreciated.

Kcmash
 
Joined
Sep 2, 2012
Messages
1,523
Reaction score
114
Location
Blue Springs, MO
My Car
1971 Mach 1, Grabber Blue w/Argent stripes. Original 2V 351C Auto, Tilt, rear defog, Black Comfortweave Interior. Under restoration. Original colors, 4V 351C, 4-Speed, Spoilers, Magnums, Ram Air. All Ford parts.
Bump! Am I the only one with this issue?
 
Joined
Jul 27, 2021
Messages
890
Reaction score
644
Location
East Texas
My Car
1971 Mustang Mach 1 M code 351 4 speed
I have never had that issue. I would imagine that something is not right with the new blower motor. The only suggestion is to check the voltage going to it on the high setting, as far as I know, when it is in the high setting you should be getting 12 volts to it. If it is not, then something may have happened when installing it that you are now not getting 12 volts to it. Easiest thing to do would be to remove it, and outside of the car connect the new and the old directly to battery 12 volts and see how the perform outside the car where you can see them. If the new one seems slow and is not pushing much air, compared to the old one, it may just be a defective unit. tons of defective stuff is coming in from overseas now.
 
Joined
Apr 17, 2019
Messages
13
Reaction score
11
Location
West Palm Beach, FL
My Car
1973 Convertible Black on Black 351C daily driver
[url=https://ibb.co/D1Js3N3][img]https://i.ibb.co/RgFZL1L/20160829-170219.jpg[/img][/url]
OK, last year I replaced the blower motor in my heater box with a new 4 Seasons blower motor. The original had a squealing bearing, so I went with new.

Now when I run the fan in the car, it feels like it has about me 50% of the speed the original had. It is quiet, but the air speed out the vents just seems lower.

Has anyone else experienced this? Is it possibly in the fan switch on the dash? Are there electrical values I can test? Did Ford use an in line resistor on the blower that 4 Seasons has on the fan motor too?

It’s definitely AC season, so your advice is appreciated.

Kcmash
I had the same problem. the replacement was a waste of time and labor.
 
Joined
Sep 2, 2012
Messages
1,523
Reaction score
114
Location
Blue Springs, MO
My Car
1971 Mach 1, Grabber Blue w/Argent stripes. Original 2V 351C Auto, Tilt, rear defog, Black Comfortweave Interior. Under restoration. Original colors, 4V 351C, 4-Speed, Spoilers, Magnums, Ram Air. All Ford parts.
I just did the motor and used my old fan blades.

I noticed something similar on my Wifes Expedition when I replaced the rear fan. It seemed to get better with time.

kcmash
 
Joined
Feb 17, 2019
Messages
103
Reaction score
76
Location
Australia
My Car
1973 351c 2v fmx convertible
OK, last year I replaced the blower motor in my heater box with a new 4 Seasons blower motor. The original had a squealing bearing, so I went with new.

Now when I run the fan in the car, it feels like it has about me 50% of the speed the original had. It is quiet, but the air speed out the vents just seems lower.

Has anyone else experienced this? Is it possibly in the fan switch on the dash? Are there electrical values I can test? Did Ford use an in line resistor on the blower that 4 Seasons has on the fan motor too?

It’s definitely AC season, so your advice is appreciated.

Kcmash
In Australia, Ford factory blower motors and scrolls were upgraded when a/c was added. This was due to having to push or pull air through two coils instead of just the heater coil hence the a/c blower created more airflow.. You can test the speed of the new motor with a handheld tachometer and/or an airflow meter, and do the same on the old motor to compare them. Maybe you could find someone to rebuild the old blower motor.
 

Bobby

Well-known member
Joined
Sep 24, 2018
Messages
247
Reaction score
86
Location
League City, TX
My Car
1972 Mach 1
Having watched a YouTube video, I discovered that there were two different blower motors that were used. One was the factory A/C - Heater blower motor and squirrel cage and two was the Heater only blower motor. I purchased a complete repro system but I had to purchase the blower motor separately. once installed it did not blow any air thru the vents. I figured maybe the polarity was somehow reversed. After swapping the red and black (grounding the red and attaching the black to the speed resistor) I got some decent air flow but not great. As previously mentioned, the heater and the A/C took two separate motors. The heater only motor has a lower RPM because it is pushing air to two vents for the heater or two vents for the defrost. The A/C motor had a higher RPM for pushing air thru 4 A/C vent. So I believe all the reproduction A/C motors by Four Seasons is actually heater only motors. I contacted Classic Auto Air and spoke with one of the engineers or a tech. I tried to tell him of the issues but he, being the smartest person in the room, told me that the old Fords from the 1970s had weak blower motors. Having grown up in the 1970s and spending quite a bit of time in 70s eras cars, I knew better than that. That idiot wouldnt listen and just blew me off.
 
Joined
Sep 2, 2012
Messages
1,523
Reaction score
114
Location
Blue Springs, MO
My Car
1971 Mach 1, Grabber Blue w/Argent stripes. Original 2V 351C Auto, Tilt, rear defog, Black Comfortweave Interior. Under restoration. Original colors, 4V 351C, 4-Speed, Spoilers, Magnums, Ram Air. All Ford parts.
That is helpful information. Considering I bought this car from the original owners I know it had the correct motor and I know how strong it blew in the 80s.

I could have the wrong replacement motor as stated above. At this time I cannot recall if I switched fan boxes during restoration. The resistor for the motor is attached to the fan box, so I am curious that I may have the wrong resistor in there too.

Kcmash
 

Bobby

Well-known member
Joined
Sep 24, 2018
Messages
247
Reaction score
86
Location
League City, TX
My Car
1972 Mach 1
That is helpful information. Considering I bought this car from the original owners I know it had the correct motor and I know how strong it blew in the 80s.

I could have the wrong replacement motor as stated above. At this time I cannot recall if I switched fan boxes during restoration. The resistor for the motor is attached to the fan box, so I am curious that I may have the wrong resistor in there too.

Kcmash
I’m pretty sure that if the resistor had not been replaced, that it is probably correct. The reproduction resistors from Scott Drake will not fit physically even though they’re listed for 65-73 Mustangs.
 
Top