• Mustang Forums
  • 1965 - 1973 Classic Mustangs -General/Talk-
  • Classic Mustang Specific Tech

Weak Airflow From Hvac

  • Thread starter Thread starter Bullitt
  • Start date Start date Jun 11, 2013

Bullitt

Packin' Heat
Founding Member
Jan 13, 2000
2,743
0
47
Houston, TX
Jun 11, 2013
#1
  • Jun 11, 2013
  • #1
Been a long time since I've posted here, but finally getting my '67 A/C in working order (hasn't been functional really since I've had it). My car is a factory A/C car so it has the 3 speed switch. The ductwork is all in good shape and I haven't been able to identify any leaks. The vacuum lines are all new and motors appear to be working fine as air gets routed to the appropriate places based on the switch position.

My issue is that the airflow out of the vents is really weak. The motor seems to have 3 speeds, but the airflow even on high is just not that much. I'm not expecting airflow like a modern car, but I would at least expect to feel the air from the driver's seat...

The wiring is all brand new, so I don't think the motor is getting undercurrent or voltage unless the motor resistor is bad. Question is - if the resistor is bad, would the motor not work at all or would I get reduced speed like I'm experiencing?

If the airflow is just the way it is, is there any blower motor upgrade out there that fits in the factory box? I'd like to avoid the expense of a complete redo on the system if possible.

Any input would be appreciated!
 

Rusty67

20+ Year Stangneter
Dec 3, 2002
3,749
37
109
LA, CA
Jun 11, 2013
#2
  • Jun 11, 2013
  • #2
Hmm, I would check the air flow at the source just to start. Pulling that box out is a total pain. Maybe disconnect the main duct to it and stick your hand up there to feel the pressure ? I'm sure there are places that can rebuild the electric fan motor and upgrade the CFM output either with faster motors or a more efficient fin design on the fan.
 

iskwezm

10 Year Member
May 24, 2005
4,159
20
79
Rowland Heights,California
Jun 11, 2013
#3
  • Jun 11, 2013
  • #3
the resistor will reduce the voltage to the motor lowering the speed. Measure the voltage at the motor.
 

horse sence

15 Year Member
Nov 29, 1999
12,191
8,014
233
Wile Coyote's stunt double
Jun 11, 2013
#4
  • Jun 11, 2013
  • #4
one of the vacume diaphrams that opens and closes the inside door has an adjustable rod check and see if the door is opening all the way. also see if it is leaking between the boxes they have foam rubber between them.
 
You must log in or register to reply here.

Similar threads

Radio, Speaker Upgrades
  • TripleYellow
  • Apr 24, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
0
Views
105
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Apr 24, 2026
TripleYellow
D
Engine 85 GT Backfires through Carb
  • DienstXIV
  • Oct 3, 2025
  • Fox 5.0 Mustang Tech
Replies
19
Views
591
Fox 5.0 Mustang Tech Oct 7, 2025
85GTStangGuy
J
'96 Cobra: A/C gets weak and engine misfires under load when warm
  • jruhnke
  • Oct 22, 2025
  • SVT Tech Forum
Replies
2
Views
286
SVT Tech Forum Nov 20, 2025
nickyb
1
Engine Motor swap from a 2003 Explorer
  • 1996mustang new
  • Oct 9, 2025
  • SN95 4.6L Mustang Tech
Replies
7
Views
543
SN95 4.6L Mustang Tech Oct 16, 2025
squeak93
Who the hell puts the wrong spark plugs in a 3.8L?
  • snowstang
  • Mar 25, 2026
  • 1996 - 2004 SN95 Mustang -General/Talk-
Replies
12
Views
386
1996 - 2004 SN95 Mustang -General/Talk- Apr 3, 2026
LILCBRA
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1965 - 1973 Classic Mustangs -General/Talk-
  • Classic Mustang Specific Tech
Menu
Log in

Register

  • Forums
  • What's new
  • Media
  • Resources
  • Contact
  • Sponsor
X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?

X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?