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I checked a 69 IAM and it looks the same as our 68. I have no idea, maybe 70. I don’t have a 70 or later book. Hopefully someone will pipe in.
 

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I was thinking it might be for the blower cooling because there’s no other hole in the case.
Like this. Now we know what that case was made for. This should work since your pic also shows the smaller hole for the screw to attach it.

 

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That hole is for the same thing as the other hole, for air to blow into the fan motor to keep the motor internal parts cool!! Looks like it needs a later air tube, good luck!
 

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POA VALVE.
What does a POA valve do?
All air conditioning systems have something built into the system to prevent the evaporator from getting so cold that it freezes up. In some systems, this mechanism is a thermostat, but in most mid 60's to mid 70's GM vehicles, it's a POA (Pilot Operated Absolute) Valve.

A thermostat prevents the Evaporator from freezing by cycling the compressor on and off based on evaporator temperature. A POA Valve prevents the evaporator from freezing by by-passing excessive system pressure. Note that in a POA Valve type system, the compressor runs constantly whenever the air conditioning system is operating.



 

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Discussion Starter #29
Yes it is
I'm trying to replace almost everything and Id'ing can be difficult! I really appreciate the help! On the Rock Auto website it lists a blower motor relay and an A/C compressor relay and they look identical. The "Standard Motor Products" has both. but they share the same part number. Is there an A/C compressor relay also hiding somewhere that I haven't discovered yet?
 

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Discussion Starter #30
POA VALVE.
What does a POA valve do?
All air conditioning systems have something built into the system to prevent the evaporator from getting so cold that it freezes up. In some systems, this mechanism is a thermostat, but in most mid 60's to mid 70's GM vehicles, it's a POA (Pilot Operated Absolute) Valve.

A thermostat prevents the Evaporator from freezing by cycling the compressor on and off based on evaporator temperature. A POA Valve prevents the evaporator from freezing by by-passing excessive system pressure. Note that in a POA Valve type system, the compressor runs constantly whenever the air conditioning system is operating.



Should I keep my original POA valve or does it need an upgrade? Also, How do I know if the old system was converted to R134? My Compressor says 57087. Lastly what is that big black ball on the passenger side inner fender? Is that part of the A/C system? It takes a vacuum line.

699754
 

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Should I keep my original POA valve or does it need an upgrade? Also, How do I know if the old system was converted to R134? My Compressor says 57087. Lastly what is that big black ball on the passenger side inner fender? Is that part of the A/C system? It takes a vacuum line.

View attachment 699754
The POA question is the million-dollar question. If the system is closed and still has some refrigerant in it, It may be ok. You can test your poa, see this thread. POA Valve Testing. I had some better threads on testing, but can't find them. I no longer recommend using a poa eliminator valve. Better results are seen on this system with the poa valve.

If your system was converted to r134, you should have adapter fittings on your charging ports. I don't see them on your system.

If you want to do it right the first time, rebuilding your poa or at least testing it is recommended. What refrigerant do you intend to use? The poa pressure needs to be set for a specific refrigerant. I'll work on finding the thread or right up another on testing and resetting the poa.

The plastic ball is a vacuum reservoir. It should be connected to a vacuum source and has a line that leads to the a/c control head which switches the vacuum to control the vacuum-operated doors on the a/c heater box.

The number you quoted on the compressor is the part number.

If you intend to use r134, then you should upgrade your hoses to vapor barrier type a/c hoses specific for r134.
 

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I'm trying to replace almost everything and Id'ing can be difficult! I really appreciate the help! On the Rock Auto website it lists a blower motor relay and an A/C compressor relay and they look identical. The "Standard Motor Products" has both. but they share the same part number. Is there an A/C compressor relay also hiding somewhere that I haven't discovered yet?
This a 69 a/c diagram. Bill might have on for a 68. I think they're near-identical. You'll notice a blower relay and no compressor relay. This also shows the vacuum hoses and connections you asked about.

699755
 

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This a 69 a/c diagram. Bill might have on for a 68. I think they're near-identical. You'll notice a blower relay and no compressor relay. This also shows the vacuum hoses and connections you asked about.

View attachment 699755
Mostly the same Al. 68 didn't have the water valve as shown in your 69 but in all they are pretty much the same.
ac wiring.jpg
 

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Just one more thing, if you want originality the vacuum ball is not used in 68 nor did it mount on the inner fender. If you look at my picks you will see a short "CAN" not a ball that attaches to the engine side of the housing for vacuum storage. Now that we know you have a 70-72 style housing that may not allow the same location but I am sure you can figure out what will work. You can use either, it just comes down to originality level that you want.

DON'T FORGET A NEW DRYER
 

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Discussion Starter #36
Are you saying my system isn’t original? That would be very hard for me to believe but I guess anything’s possible. What is this 70-72 housing you speak of?

I do know my car is a factory A/C car, but why would anyone refit the components to whatever it is you think I have?

I’m not sure I follow you here....?
 

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Just one more thing, if you want originality the vacuum ball is not used in 68 nor did it mount on the inner fender. If you look at my picks you will see a short "CAN" not a ball that attaches to the engine side of the housing for vacuum storage. Now that we know you have a 70-72 style housing that may not allow the same location but I am sure you can figure out what will work. You can use either, it just comes down to originality level that you want.

DON'T FORGET A NEW DRYER
A quick search on the ball shows some cars had them. I’ll check for a date code on mine. '68 AC Vacuum Canister - Ball or Coffee Can? Which...
If you don't find a date code we can date most parts using the gmwiki search...GMPartsWiki -
 

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Are you saying my system isn’t original? That would be very hard for me to believe but I guess anything’s possible. What is this 70-72 housing you speak of?

I do know my car is a factory A/C car, but why would anyone refit the components to whatever it is you think I have?

I’m not sure I follow you here....?
The can or ball was never installed on the inner fender it was always installed on the side of the housing. I don’t remember seeing a ball on anything prior to 70. Who knows why a previous owner did something that wasn’t original. I am sure your car is factory AC but someone changed stuff just like you did using a 70-72 housing.
 

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Discussion Starter #40 (Edited)
The can or ball was never installed on the inner fender it was always installed on the side of the housing. I don’t remember seeing a ball on anything prior to 70. Who knows why a previous owner did something that wasn’t original. I am sure your car is factory AC but someone changed stuff just like you did using a 70-72 housing.
Got it!

So I grabbed the ball, and took it out to see if the mounting pad and holes would align with the original case. The factory case has 2 holes where you said the canister (or ball) should mount. It's a perfect match! One of those factory holes looks abused and cracked which might explain why the ball was relocated.

The new case was purchased from opgi and they advertise it as a 68-72. The reality is, the case is really a repop of a 71-72 but because the basic shape is a match as it relates to the firewall, opgi markets for 68 through 72. Does this sound right to you guys? The new case only has 1 hole in the same location that the vacuum canister should go.

Evap case.png
 
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