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1976 Cadillac Series 75 A/C ?

2K views 10 replies 4 participants last post by  Coodeville 
#1 ·
Tried finding my old post but I couldnt. The pressures are 45 and 130 psi at 101 degrees. The evaporator inlet is cold and the outlet is warm. Air is coming out of the vents warm. Had the programmer rebuilt but it didnt help. Un mounted the programmer but left it connected so that I can feel the air directly off the evaporator which is coming out cold with some warm air at times coming out too. Put an external vacuum source onto a brand new heater valve and it still comes out warm. Whats your next suggestion ?
 
#2 ·
with cadillac programmers... there is an adjustment for the rod that controls the blend door..

i wonder which heater valve you got.. i looked up the application and vacuum does close the flow.. but there is an identical version that opens with vacuum.

do you have a service manual that covers the HVAC on 72 to 76 models?? should be really close to being the same. if not i can dig my mitchell Hvac manual out but it keeps getting put away deeper and deeper into the boxes.. not me doing it..

this is for a 1971.. but i think the programmer and most of the instructions are the same..

1971 Cadillac Shop Manual- AC and Heating Page 84 of 106

1971 Cadillac Shop Manual- AC and Heating Page 85 of 106

this page describes the air blend door link adjustment..


actually this section describes the series 75 HVAC there is a turn page link at the top.. 1971 Cadillac Shop Manual- AC and Heating Page 86 of 106

but it might be totally wrong for your 1975 seventy five series..

sorry if i have not answered your post with what you ask..
 
#7 ·
I just removed the heater core from the system and manually operated the blend door. It didnt make a difference. My pressurres are 40 psi and 140 psi. Is the whole VIR suppose to get cold like an accumulator ? In the picture, I'm pointing to the evaporator inlet which is the only cold part of the VIR. I managed to get my fingers onto the evaporator and its not cold at all. I replaced the VIR with a rebuilt unit from Classic Air and I'm now wondering if they did it correctly. Been a long time since i had a car with a VIR. Most have had expansion valve and dryers or an accumulator.
 

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#8 ·
The compressor is fully engaged at all times since its not a CCOT system. I wish it were a CCOT system. To my knowledge, I put 4.5 pounds of freon into it. It took a hell of a long time for it to go in. I'm reading the book now. I have the factory manual for a '76.
 
#9 ·
4.5 lbs in that system is a over charge. With a VIR system your low pressure should be around 28 lbs. I loved those VIR systems! Everything in a can. That vehicle should take 3.75 lbs of R12. To test the VIR run the engine at 1500 rpm and disconnect the blower motor. The low pressure should maintain itself between 28-32 lbs. If you have a bad POA valve in the VIR pressures will drop and eventually will go to zero. There should be a tag on the evap case with the proper charge. Bleed off some refrig and see if it gets colder. There is a sight glass on the VIR. Bleed off until you see the first bubble. Your charge will be close.

I can't remember if the vacuum opens or closes the heater valve. With the system set to 65 degrees the blend door should be fully closed. Check to see if there is vacuum at the heater valve . If there is, the valve is a vac to close.
roll the thumb wheel to max heat. The blend door should be in the open position. If you have vacuum at the valve you have a vac to open type valve. Once you determine which valve you have, to test it remove it from the car and blow through it. You either can or can't depending on which type. Now apply a vac to the valve (use a Mitivac) and you will know if the valve is good or bad.
If your blend door doesn't fully close at 65, there is a potentiometer under the thumb wheel that can be adjusted with a special tool. The tool is flat with small teeth on one end that swipes across the gear on the pot to adjust the programmer.

The first thing I would do is to get the proper amount of refrig in the system.

First rule of thumb with A/C is ,"More refrig ain't better!"

BB :thumbup::thumbup:
 
#11 ·
Final results of todays work on the Series 75

Low is 45
High is 155
Ambient is 88
Evaporator is 38 to 45 degrees.
System is cold to the hand

What did I do ? I added more R12. I guess I didn't have enough in to begin with ? The guage readings seem to change greatly when its 110 out and I thought it was charged. Anyhow, the VIR doesnt get cold te way an accumulator does. What I did notice though is that the frozen line unfroze as i added more R12 and the evaporator temp dropped big time. I did a leak test in te front of the car and it was OK. There are AC lines running under the car and to the rear AC unit too that I didnt leak test. I'll do that another time. I'm just happy its cold now........leaks I can handle.


I want to thank everyone who helped me on this. Its been 30 years since I worked on a VIR system. I wish this was a CCOT or regular X Valve system
 
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