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Discussion Starter #1
My AC is blowing cold air out of the defroster and the floor vents ONLY. I replaced the vaccum line on the intake manifold as i heard that would cause this problem. How much troble is it to check the vaccum lines that feed in to the controller?:(
 

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I don't know or should say have not taken a 96 a part, but for the 84-89 it was as simple as removing the dash pad and using a dentist type mirror to check the hoses going to the vents.
 

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Discussion Starter #3
Thanks for the information, I hope mine is in the same place. I really need a GM manual.
Louis:(
 

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Hopefully VetteTech81 will see this thread since he works on vettes or do a search for him and PM him for help and point him here...
 

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do you have the manual a/c controll head or the automatic climate control.. if its the manual I would imagine that you could remove the console trim and the trim around the radio and a/c controlls and then remove the controll head and check the connections to the back of the controll head and check to make shure you have supply vaccum..

can you get heat out the vents.. I am assuming that anytime you have the blower on it is diverting the air to the def. and floor vents is that correct?
-Rick
 

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Discussion Starter #6
Cold or Hot the blower only exits from defroster and lower ducts, and I have the Climate Control option. It started last year and after I drove a few miles all was fine and the Cruise Control always worked. Now the air is coming out as I wrote above and now the cruise control does not work(never did this until the other day). A corvette Tech asked me if the cruise was working when I asked what was wrong and he advised me that the Vaccum controler was BAD (really sure) I have talked with other C4 owners and several said that there was only a leak.( I did not want to tell them that I did not know where the Controller was) and he said the controller was several hundred dollars plus labor. OUCH! Just did the water pump opti-spark, plug wires etc on the wifes TA. Trying to fix this my self. Thanks Louis:(
 

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LAB said:
Cold or Hot the blower only exits from defroster and lower ducts, and I have the Climate Control option. It started last year and after I drove a few miles all was fine and the Cruise Control always worked. Now the air is coming out as I wrote above and now the cruise control does not work(never did this until the other day). A corvette Tech asked me if the cruise was working when I asked what was wrong and he advised me that the Vaccum controler was BAD (really sure) I have talked with other C4 owners and several said that there was only a leak.( I did not want to tell them that I did not know where the Controller was) and he said the controller was several hundred dollars plus labor. OUCH! Just did the water pump opti-spark, plug wires etc on the wifes TA. Trying to fix this my self. Thanks Louis:(
Well if you have the electronic climate controll I think the vent doors may be electronic.. I will see what I can come up with tomarrow.. there maybe 2 seperate problems between the a/c and the cruise but we'll see.. I will try to get some more info at work..
-Rick
 

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Discussion Starter #8
Rick,
Thanks for taking the time to help out. I am tring to purchase a used set of GM factory repair manuals. Last vear I was told how to acess fault codes from the dash on the Climate Control tried that but no fault codes ( I may not have done this correctly)Thanks agsin for your help.
Louis
 

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El Teafive
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Okay, Here is the Deal.. Cruise control and AC both work off of Vacuum.

The cruise control works off of direct vacuum from the intake manifold, the A/C does the same but it goes through a check valve. I would suggest replacing the check valve, it keeps vacuum on the A/C side so it does not change as much during different intake vacuum pressures.

First replace the check valve, (smaller part, has 3 vacuum ports I think)


As for the electronic climate control, if the check valve is good, then it may be the AC Programmer (not the Control head) the programmer sits just above the accelerator pedal. the programmer basically takes the electronic info and engerizes or de-energizes Solenoids for vacuum

The Programmer is in the $100-$150 range I think..

Hope this helps
 

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Discussion Starter #10
Thanks Jeff,
Is the check valve the one on the manifold on the passenger side on the intake at the end of the intake manifold? And is there a difference because I have the LT4??:(
Louis
 

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El Teafive
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Originally posted by LAB ...<br>
Thanks Jeff,
Is the check valve the one on the manifold on the passenger side on the intake at the end of the intake manifold? And is there a difference because I have the LT4??:(
Louis<br>
Could be at either side, on my L98 it at the back Driver side Fuel rail (near it)
 

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You have to bend your body in ways you thought never possible to replace it, but it is possible. It is above the accel pedal (a square black box with a bunch of multi-colored vaccum tubes coming out the top). Mine went out this spring (having the same symptoms as you) and I just replaced it a couple of weeks ago. Apparently this is a very common problem on the 1996's. GM does not make it anymore, so you have to find one. I got mine through Just Corvettes(a salvage yard) for 150. Took me several hours and a sore back to get the job done, but it works like a charm now. Hope this helps.
 

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El Teafive
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arichard said:
You have to bend your body in ways you thought never possible to replace it, but it is possible. It is above the accel pedal (a square black box with a bunch of multi-colored vaccum tubes coming out the top). Mine went out this spring (having the same symptoms as you) and I just replaced it a couple of weeks ago. Apparently this is a very common problem on the 1996's. GM does not make it anymore, so you have to find one. I got mine through Just Corvettes(a salvage yard) for 150. Took me several hours and a sore back to get the job done, but it works like a charm now. Hope this helps.
REALLY? GM DOESN'T Make them anymore!!

Good thing I have about 3 of tem floating around. LOL

I agree you need to bend goofy to get to it, but if you pull out the Driver seat it makes it easier.
 

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Buy brand new Service ManualsHERE. or try Corvette Central.
 
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