Factory AC cab, should there be a constalt Breeze on the knees?

classic Classic list List threaded Threaded
9 messages Options
Reply | Threaded
Open this post in threaded view
|

Factory AC cab, should there be a constalt Breeze on the knees?

reamer
I have noticed with my Factory AC equipped cab (ac not operatable right now) No matter where the slide handle on the AC dash control, (even in the "off" position) I get a considerable breeze on the floor, amount of flow is dictated by speed.
I thought in the "off" position no breeze should be coming from the cowl. true?

Thanks
1986 F-150 Flareside 4x4, 351, 4-v, ZF5 speed. AC, Cruise, Tilt, Slider, Digital clock, Radio, Lariat seat, Pwr doors/locks
Reply | Threaded
Open this post in threaded view
|

Re: Factory AC cab, should there be a constalt Breeze on the knees?

Dorsai
Are your kick panel vents open perchance?
Matthew
1980 F-150 Custom 2wd longbed, 300-6, C6, 2.75 rear axle
Atlanta GA
Reply | Threaded
Open this post in threaded view
|

Re: Factory AC cab, should there be a constalt Breeze on the knees?

grumpin
In reply to this post by reamer
Vacuum leak?
Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona
Reply | Threaded
Open this post in threaded view
|

Re: Factory AC cab, should there be a constalt Breeze on the knees?

reamer
On This AC cab, there are metal "seal-off" plates at the right and left kick-panel vents….
The breeze is coming from under the center of the dash at the plastic vents....
1986 F-150 Flareside 4x4, 351, 4-v, ZF5 speed. AC, Cruise, Tilt, Slider, Digital clock, Radio, Lariat seat, Pwr doors/locks
Reply | Threaded
Open this post in threaded view
|

Re: Factory AC cab, should there be a constalt Breeze on the knees?

1986F150Six
Administrator
Are any firewall rubber grommets missing or torn?
Reply | Threaded
Open this post in threaded view
|

Re: Factory AC cab, should there be a constalt Breeze on the knees?

packagerjr
In reply to this post by reamer
It’s possible the tab on the vacuum switch that kills power to the blower motor is broken, making those contacts closed all the time.  In this pic, the short tab is operated by the big ramp and that kills power to the blower motor speed switch.  Applicable to my 1980 but likely very similar regardless of year.

Is the breeze related to fan speed?
1980 Bronco Ranger XLT, 351M, C6.  They call me Ferguson.
Reply | Threaded
Open this post in threaded view
|

Re: Factory AC cab, should there be a constalt Breeze on the knees?

Steve83
Banned User
In reply to this post by reamer
reamer wrote
...breeze on the floor, amount of flow is dictated by speed.
I thought in the "off" position no breeze should be coming from the cowl. true?
No.  The HVAC system is designed failsafe - if the whole thing shuts down (or is turned to OFF), driving forward still ventilates the cab.  It's specifically described in the owner's manual.  The pressure of the air hitting the w/s pushes that breeze down through the wiper cowl, through the fresh/recirc door (which defaults to FRESH), through the evap., past the temperature blend door (wherever you have it mechanically set), and out the FLOOR & DEFROST registers (the default of the diverter doors).  It exits the cab through the louvers in the lower rear of the doors, and then out the louvers under the latches, into the airstream along the sides of the body.
Reply | Threaded
Open this post in threaded view
|

Re: Factory AC cab, should there be a constalt Breeze on the knees?

81f100custom
This post was updated on .
I would have to disagree as mine has no air flow at all in the off position. Some of the chevys I have do operate as you describe in the off position they still have air flow when you drive down the road. If you look at this diagram I believe if I am seeing it right there will be no air flow driving down the road when in the off position. In the off position you will have vacuum on 7A and 7B which in return closes off the defrost ducts. You will not have vacuum on 6 which shuts off air to the instrument panel registers. You will have vacuum on the outside recirculate door which seals any air flow from the outside if the system seals properly. Also there will be no power on the system in the off position so no blower motor moving any air. If you loose vacuum or have no vacuum then yes the recirculate door will open and you will have flow as you drive down the road and force air in. I am assuming he has vacuum on the system.
 
Eddie,
81 F100 Custom SWB, 5.0L, 4x2, Single Rail Four-Speed Overdrive, 3.00 Non-Limited Slip Rear Axle, Non A/C truck to complete 85 F150 factory A/C conversion, Nutmeg interior color.
Reply | Threaded
Open this post in threaded view
|

Re: Factory AC cab, should there be a constalt Breeze on the knees?

Steve83
Banned User
It looks like I must have remembered the GM function then - that shows the fresh air is blocked in OFF.  So the original problem is likely the same UV-degraded white recirculate motor vacuum line that causes the A/C to switch to the defrost registers under hard acceleration (low vacuum):