So i was driving my truck today and went to circulate some air through the truck without using the a/c and the air would only come through my defrosters not through any of the other vent when i would change the option to have it go through the other vents. Any ideas? Vac problem?

 

Yes, you've got a vacuum problem. Usually something in the 4WD system, like the hubs. But a lack of vacuum will definitely cause that issue.

 

Sounds like a VAC issue to me also.


PINPOINT TEST G: INCORRECT/ERRATIC DIRECTION OF AIRFLOW FROM OUTLET(S) — MANUAL CLIMATE CONTROL
Test Step Result / Action to Take
G1 CHECK THE SYSTEM AIR FLOW
Key in START position.
Set the blower motor speed to maximum.
Check for proper air flow in each function selector switch position at engine idle and under acceleration.
Is there air flow only from the defroster outlets in each function selector switch position?
Yes
GO to G2 .

No
GO to G14 .
G2 CHECK FOR VACUUM SUPPLY AT THE RESERVOIR
Disconnect: Vacuum Reservoir Inlet Hose.
Key in START position.
Check for vacuum at the vacuum reservoir inlet hose.

Is there vacuum?
Yes
GO to G8 .

No
For gasoline engines, GO to G3 .

For diesel engines, GO to G4 .
G3 CHECK THE MANIFOLD VACUUM HOSE FOR BLOCKAGE
Key in OFF position.
Connect a vacuum pump to the manifold vacuum hose and try to pull a vacuum. If the pump pulls and holds a vacuum, the hose is plugged. If the pump pulls a vacuum that slowly decays, the hose is restricted.

Is the vacuum reservoir inlet hose plugged or restricted?
Yes
INSTALL a new vacuum hose. TEST the system for normal operation.

No
REPAIR the leaking vacuum hose. TEST the system for normal operation.
G4 CHECK THE VOLTAGE AT THE VACUUM PUMP
Key in OFF position.
Disconnect: Vacuum Pump C1119.
Key in ON position.
Measure the voltage between the vacuum pump C1119 pin 4, circuit 295 (LB/PK) and ground.

Is the voltage greater than 10 volts?
Yes
GO to G5 .

No
REPAIR circuit 295 (LB/PK). TEST the system for normal operation.
G5 CHECK THE VACUUM PUMP GROUND
Key in OFF position.
Measure the resistance between the vacuum pump C1119 pin 2, circuit 57 (BK) and ground.

Is the resistance less than 5 ohms?
Yes
GO to G6 .

No
REPAIR circuit 57 (BK). TEST the system for normal operation.
G6 CHECK THE VACUUM RESERVOIR INLET HOSE FOR BLOCKAGE
Disconnect: Vacuum Reservoir Inlet Hose.
Connect a vacuum pump to the vacuum reservoir inlet hose and try to pull a vacuum. If the vacuum pump pulls and holds a vacuum, the hose is plugged. If the vacuum pump pulls a vacuum that slowly decays, the hose is restricted.

Is the vacuum reservoir inlet hose plugged or restricted?
Yes
INSTALL a new vacuum reservoir inlet hose. TEST the system for normal operation.

No
GO to G7 .
G7 CHECK THE VACUUM RESERVOIR INLET HOSE FOR A LEAK
Plug the vacuum reservoir inlet hose.

Leak test the vacuum reservoir inlet hose using the vacuum pump.

Does the vacuum reservoir inlet hose leak?
Yes
INSTALL a new vacuum reservoir inlet hose. TEST the system for normal operation.

No
INSTALL a new vacuum pump. TEST the system for normal operation.
G8 CHECK FOR VACUUM AT THE COWL HARNESS CONNECTOR
Connect: Vacuum Reservoir Inlet Hose.
Disconnect: Cowl Vacuum Harness Connector.
Check for vacuum at the cowl vacuum harness connector.

Is there vacuum?
Yes
GO to G12 .

No
GO to G9 .
G9 CHECK THE VACUUM RESERVOIR OUTLET HOSE FOR BLOCKAGE
Key in OFF position.
Disconnect: Vacuum Reservoir Outlet Hose.
Connect a vacuum pump to the vacuum reservoir outlet hose and try to pull a vacuum. If the vacuum pump pulls and holds a vacuum, the hose is plugged. If the vacuum pump pulls a vacuum that slowly decays, the hose is restricted.

Is the vacuum reservoir hose plugged or restricted?
Yes
INSTALL a new vacuum reservoir outlet hose. TEST the system for normal operation.

No
GO to G10 .
G10 CHECK THE VACUUM RESERVOIR TANK FOR BLOCKAGE
Connect a vacuum pump to the vacuum reservoir tank inlet (VAC port) and try to pull a vacuum. If the vacuum pump pulls and holds a vacuum, the tank is plugged. If the vacuum pump pulls a vacuum that slowly decays, the tank is restricted.

Is the vacuum reservoir tank plugged or restricted?
Yes
INSTALL a new vacuum reservoir tank. REFER to Section 412-04 . TEST the system for normal operation.

No
GO to G11 .
G11 LEAK TEST THE VACUUM RESERVOIR TANK
Connect a vacuum pump to the vacuum reservoir tank outlet port and try to pull a vacuum.

Does the vacuum reservoir tank leak?

 

If you need more just PM me.

 

Normally a cracked hose/line near the vacuum pump on the passenger inner fender.

 

I have the same problem in my 06 EXPY Limited. any new info for a lost soul here.

 

No new info, the problem still has the same causes and fixes... Usually it's a cracked vacuum line or fitting near the attachments on the passenger inner fender, take a look and see what you find. Basically you are losing the vacuum that makes the various switches that direct the airflow work. You probably also have lost auto engagement of the front hubs when you switch on 4WD. You need to find out why you have lost vacuum - either the pump is bad or it's leaking somewhere.

Brian