dmhoo29

With my A/C controls all off, air still blows out the vents. While idle it does not. just while driving. If I turn it on the air will only blow out the front vents and nothing out of the floor or defrost if you place it in floor or defrost position.

Any help would be appreciated.

MT-2500

Do you have auto or manual ac/heater controls?

Good engine vacumn to heater controls?

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Remember proper testing gives us the answer to many problems.
MT

dmhoo29

Manual. I assume the vaccum is okay. I don't hear any leaks.

MT-2500

What was the engine vaccum to controls reading?

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Remember proper testing gives us the answer to many problems.
MT

dmhoo29

Sorry, i have no way of knowing that. I'm no mechanic.

MT-2500

All you need is a vacuum gauge.
And check vacuum lines and vacuum ball for good engine cacuum

__________________
Remember proper testing gives us the answer to many problems.
MT

dmhoo29

Where's the ball located? I looked and never found one.

MT-2500

Some are right front fender area.
And some on lower part of hood.
Have a look and see.

__________________
Remember proper testing gives us the answer to many problems.
MT

dmhoo29

Let me see if I can clean up my mess.
At first the air would slightly come from the front vents when taking off and quit once you got to a set speed. If you punched the gas it would blow air but then go away once again after speed was set.
Now when you drive 10,20,30mph etc. It blows out as if it's on like the 2 setting. It does not goaway once speed is set.
I use to be able to use Defrost or floor or mix. Now the only one that works is the front a/c vents.
I checked the hoses and no leaks. I cannot find that vaccum ball everyone tells me about.

P.S. I took the glove box down to check the hoses and when I move the switch fron say floor to defrost nothing in there moves.

j cAT

your problem is most likely a defective,cracked,split rubber vacuum line...these lines run from the top of the engine to the vacuum ball,,this should be black plastic, the size of a soft ball...on ford they use the tin can...

the hoses are about 3/8 in in diameter O.D.,,,you should see many ,,remove and replace any defective..

after you do all this and repair any defective you'll notice that the engine runs smoother..maybe that ac vent control will work,, now that it has vacuum power to operate..

dmhoo29

I wish someone would show me a photo of this mysterious vacuum ball. I gave looked everywhere for it. Still cannot locate it.

old_master

98 does not use the "ball".... probably why you can't find it The vacuum reservoir is located inside the left front fender just forward of the left hood hinge. There is one 1/8" I.D. vacuum line going to it.

j cAT

you do not use your ears to find vacuum leaks.....
with a vacuum gauge you measure the vacuum and when the vacuum is below 17 inches there is a leak somewhere...

some vehicle owners just replace all the vacuum lines at the 10year life...this is when they split and give you more serious problems..

Joe Wilson

It might be the vacuum switch located just behind the knob you used to switch on AC, Vent, heater, etc. It is just a switch with a bunch of vacuum lines going into the back of it. Maybe a line has come off. The older vehicles used a vacuum ball and a switch with a cable going to it. Newer GM products (like 2004) went back to cable. Yours has the vacuum switch.