Friday, November 30, 2012


Ford Windstar HVAC system not working and hissing noise under dash is heard need vacuum line diagram to inspect vacuum leak issue

The system is blowing warm air out of the dash vents and the rear air will only blow from the bottom outlet

First inspect vacuum control switch,if its faulty,then replace it.

If problem same even after replacing vacuum switch,then other possibilities needs to be checked inspected.

1998 Ford Windstar 3.8L

NOTE:  The vacuum source is the intake manifold feeding the vacuum reservoir and the A/C picks it up from there,

See below i have mentioned the  diagram for the system, also there is an electronic actuator that operates the temp blen door, you might want to look at it.

Vacuum Control Diagram

Ford Vacuum line diagram

Item Part Number Description
1 19850 A/C Evaporator Housing
2 - A/C Evaporator Core
3 18A318 Heater and A/C Air Inlet Duct Door Vacuum Control Motor
4 18527 Blower Motor
5 18476 Heater Core
6 18C581 Vacuum Hose Harness
7 19A566 A/C Vacuum Reservoir Tank and Bracket
8 19A563 A/C Vacuum Check Valve
9 18A318 Windshield Defroster Door Vacuum Control Motor
10 18A318 Heater Air Damper Door Vacuum Control Motor

When on panel, it is the outside air along with the heat from the engine being pulled into the cabin, that's the difference,The vacuum source will come from the upper intake manifold on the passenger side rear, it will be an elbow with 2 lines attached. The black line shown in the diagram above  is the vacuum canister feed.
There will also be a black line running into the fire wall that feeds the A/C door motors.
If the compressors not coming on then you need to check for power at the cycling switch, or take a jumper wire and jump the 2 terminals and see if the compressor cycles on, is there a full charge of freon in the system?
I believe you got more than 1 problem here, start with the cycling switch first and the Freon level .,
And continue further troubleshooting to correct the issue.

These details will help.

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