How to diagnose 1998 Ford Wind star rear ac no vacuum on vac line?

Answer 1

I had the same problem on my 98 Windstar. I found out that the white vacuum line runs up to the rear ac/heat switch in the climate control in the dash. In the "Blue" area, the vacuum is supplied to the damper switch to make the air blow out the side and top vents. It also runs down to the valve under the van that cuts off the coolant runnig to the rear heater core. In the "Red" area the vacuum is cut off from the damper to only blow the air out the bottom vents. It also cuts the vacuum to the coolant cut off switch under the van and coolant flows through the heater core allowing the air to be warm. The switch is a dealer part. The switch has a built in "valve" inside that either opens or closes the vacuum supply to the white line running back to the rear unit. Usually the rubber piece wears out and does not allow any more vacuum at all. It will get soft and permanently plug the incoming vacuum supply line. I actually took out the switch and fabricated my own new rubber piece to make it work rather than pay way too much from the local Ford dealer! Be aware, it must be a hard rubber that you use or it will still fail and not supply the vacuum correctly. Good Luck!