Its actually a g series van but i know there are more truck guys on here.
89 g3500 vandura will not blow cold air. I charged and recharged againthinking i did it wrong. Not the problem.The blower motor works fine, and the ducts are all free of debris. The little vacuum assy on the back of the controls appear to be fine and working. The pressure switch is allowing the compressor clutch to come on for a few seconds and shut off for a few (if i recall, it kicks on at 25). The low pressure lines and air dryer are not getting cold or wet, even if i bypass the pressure switch, thus- the air on "A/C" is no cooler than the "vent" setting

 

Put some gauges on the system and find out for sure if the system is charged correctly. It appears not to be!

 

X2, the compressor shouldn't cycle on/off unless the low pressure cut out switch is bad, or the system is low.

 

a. there is a section in Chevy Vans and subsection: Express and G-Series Vans for this comment.

b.
1. open the hood. there is a large black vacuum bowl bolted to the underside of the hood.
2. check your vacuum reservoir for the hose that should be attached to it.
I bet it is missing, which is why your compressor comes on and the blower motor blows but you get no AC cold air distribution from the vents. Default setting is windshield defrost.
3. Most likely the rubber hoses have deteriorated, probably all dry rotted. This is maybe 1/4" or 5/16" windshield washer tubing hose. You will have to remove the doghouse to replace ALL the bad hose since it connects to a T on the back of the throttle body. 4 feet should be enough.

c. 25psi is too low a pressure to stay on. You have to charge with the car on, AC system running. Turn the can upside down as you charge it up. With one can in the compressor cycling time should double instantly.

 

How much freon did you put in it? That van takes a lot of juice; something like 3.5-4 lbs.

Allan

 

Allan I used one of those cans with the gauge right on it, I set the temp and filled it up, I'd say it took 1 can before it was in the red, by the sounds of it I am too low, how much is 3.5-4 lbs actually? Also the brown hose on the back of the control panel has vacuum if that means anything. I appreciate everyone's help!

 

The vacuum hoses, the control, the reservoir and the gauge on the filler apparatus means nothing. Just a bunch of smoke and mirrors to your problem. I.E. the system isn't getting cold.


"IF" the compressor is cycling on and off rapidly, it is trying to cool, but can't. Needs more freon.

However:
<O</O
If this were my van, the first thing I would do is drain 'er down and pull that orifice tube to make darned sure it isn't plugged with mud.....clean it or replace. (The reason I say this is that if it is plugged, one can is gonna make it act like it is full.)
<O</O

Then reassemble and put a can of freon in the system. That will give you just enough pressure to trip the low pressure switch and to engage the compressor.

<O</OStart the engine and continue filling until the receiver is cold to the touch (rather painful to hold your hand on it for any amount of time).

<O</OIf the van has the original receiver, there should be a yellow/black sticker on top that tells you the charge. Guarantee you it's gonna take at least 3 and probably more like 4 cans to get 'er full. That's a big van.

<O</OAllan<O</O

 

if you have rear AC then it takes 48 ounces which is 3 lbs, if not rear AC then it about 2.5. Then you have to consider the size of the cans you are charging, most cans are 12 ounces, some are 16-18 ounces. this tells you how many cans you will need.