Vaccum- A/C - 4WD

[chastity]

Hello,

I need advice on where to start looking for the following problems.

1. A/C blows from Defrost /Floor upon Acceleration.

2. Vents in Normal mode Idling Blow thru center vents and Floor even tho it's set to max. Also It's sucking fresh air thru Max setting. ( is that Normal)

I have replaced all vacuum lines under the hood.

I don't know where else to look for Vacuum lines.

I do know the Transfer case Acuater needs to be replaced per the local transmission shop. The front drive shaft turns but wheels do not when on the lift. Says the Hubs are not locking.

Is he telling me the truth? or could it be something else?

Not sure if the Transfer Case Actuator is also the cause of my vacuum issue either.

Any help would be appreciated.

Thanks,

Chas

[old_master]

The HVAC and the 4WD are supplied with vacuum through the same vacuum line and both use the same check valve and reservoir. If the actuator is leaking vacuum, it's likely the HVAC will not distribute the air correctly, when the vehicle is in 4WD. If there is a leak, or poor vacuum to the reservoir, the HVAC will act up AND the 4WD will not engage. From what you describe, there's a vacuum leak that is probably causing all of your problems. Air flow changing to defrost on accelleration is a classic symptom of a vacuum leak also because the system defaults to defrost with no vacuum. What year & model, and do you have Automatic Climate Control or Manual AC?

[chastity]

Oh it's a 1995 S10 Blazer LT

well upon searching through the forums here I removed the battery and the tray to check out the actuator because I was told it needed to be replaced before my 4WD will work. well I pushed the cable back and forth and the rubber boot on the actuator it made a swishing sound like there is a definite leak there?

The A/C is Manual. But Fresh air blows constantly on my feet while driving is that Normal? and when the A/C is on it blows thru the floor and the vents as if I had it in blend mode?

Also when I first turn the A/C on I have to turn to vent wait til it blows out and then to A/C otherwise it only blows through the Defrost and Floor..


Thank you,

Chas

[old_master]

The best test for the actuator is to remove the vacuum line from it. Then connect a piece of vacuum line to it and suck on it. The cable to the front axle should move approximately one half inch and the actuator should hold vacuum indefinitely.

There should not be any oil in the actuator or the vacuum line to it. If there is, the vacuum switch on the transfer case needs to be replaced, along with the vacuum lines, the vacuum reservoir, and the actuator. In severe cases, oil can reach the HVAC controls in the dash. If this happens, the vacuum lines in the dash, along with the mode switch, will need to be cleaned or replaced. If there is oil in the lines to the HVAC and/or 4WD, it can cause both to be inoperative, operate sluggishly, or cause the air flow not to come out where you direct it to.

[chastity]

Update:

had the new Actuator installed today then spent 3 hrs looking for a vaccum leak we could not find. because the front wheels would not lock when put in 4WD. we finally figured out it was the Transfer case switch (which was replaced about 3 weeks ago) put New switch in and I have 4WD now.

But still there is air constantly flowing on my feet when im driving even when the A/C isn't on. when the A/C is on the air blows from the vents and Floor even tho it is on MAX A/C and upon acceleration it defaults to defrost and Floor. Ive been reading about Blend doors and ventilation doors? but I don't know where to even look for them any help would be greatly appreciated.

Thanks,

Chas

[old_master]

The blend door servos, (actuators) and recirculate servo, are all in the dash. If I remember right, there are three servos: Recirc servo, above passenger's feet. Heat/defrost servo, driver side of center, just above floor, below radio. Mode valve servo, on top of heater case, left of center, behind radio. Each one has a small line attached to it, some have two lines. Each vacuum line and each vacuum diaphram in each servo should hold vacuum and freely operate its respective blend door. The mode switch has several lines connected to the back of it. The vacuum supply line must have vacuum whenever the engine is running, and should hold vacuum when the engine is off. Guaranteed you'll find a vacuum leak somewhere.

[chastity]

im looking for the leak I can not find it checked all the vacuum lines under the hood even tho they all have been replaced. but i do hear a hissing sound from the center of the dash. that could be where it is. im not looking forward to having to remove the dash had all the kick panels and the radio out today trying to get to it but couldnt get there.

not even sure where to start on removing the dashboard either.

but now my break pedal sometimes goes to the floor and when i hit the gas and if i have to make a sudden stop right after the pedal gets really hard. is that part of the vacuum leak im looking for?

thanks for your help....