# ac help 1969 gto



## 8222raspashillrd (Jul 22, 2018)

Hi i am new here and have a 69 with factory ac Frigidair compressor. im assuming the low pressure is next to the compressor on the aluminum pressure bottle mounted to the compressor. I am not a fan of running R134 in vintage compressors. The ac is cool but the pressure bottle and compressor get quite hot which seems wrong. any help is appreciated.


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## BearGFR (Aug 25, 2008)

It's normal for the high pressure side of any system to get really hot. You should be able to tell which is which by following the lines coming out of the compressor. The path that goes from the compressor to the condenser coil in front of the radiator will be the high pressure side. From the condenser, going (eventually) back to the evaporator coils in the passenger compartment without going back through the compressor will be the low pressure side.

Bear


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## 8222raspashillrd (Jul 22, 2018)

i just bought this car its a one owner from calif. There are retro fit 134 fittings on the car but this is what is confusing me because they appear to be reversed based on your reply. the high pressure fitting is on the rear line going to the firewall and low pressure is on the compressor expansion tank going to the front. Do you know if these fittings have specific theads for high pressure/ low pressure or can they be installed on either line?? I have worked on ac before but never seen a system like this and there is virtually no information i can find online. I appreciate your help. thanks


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## PontiacJim (Dec 29, 2012)

8222raspashillrd said:


> i just bought this car its a one owner from calif. There are retro fit 134 fittings on the car but this is what is confusing me because they appear to be reversed based on your reply. the high pressure fitting is on the rear line going to the firewall and low pressure is on the compressor expansion tank going to the front. Do you know if these fittings have specific theads for high pressure/ low pressure or can they be installed on either line?? I have worked on ac before but never seen a system like this and there is virtually no information i can find online. I appreciate your help. thanks



Your best bet is going to purchase a 1969 Service Manual reprint or Service Manual on CD. They show you the AC system as well as servicing the system. It should answer all your questions.

The parts suppliers like Ames, OPGI, and Ebay should have these. It is the only way to go if you work on your car or plan to keep it long term. :thumbsup:


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## BearGFR (Aug 25, 2008)

Sounds backwards to me.. On my R134a system, the high pressure fitting is red and is a larger diameter than the low pressure fitting, which is blue. I haven't worked on an R12 system but I -think- both sides use the same fittings, so you have to be careful and know what you're doing when working on them. I found an online site that allowed me to get certified to purchase R12, but haven't used it yet.


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## 8222raspashillrd (Jul 22, 2018)

thank you i will get one. i plan on keeping this car for quite awhile. ive always loved gto and found a beautiful original one.


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## PontiacJim (Dec 29, 2012)

Just for the heck of it, I was looking to see who offers the Service Manuals. Found that RockAuto even offers them. I do get "older" parts from RockAuto and have not had a problem yet and their prices - always seem to be very reasonable. Sometimes they have the part where no one else does. :thumbsup:


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## LATECH (Jul 18, 2018)

8222raspashillrd said:


> Hi i am new here and have a 69 with factory ac Frigidair compressor. im assuming the low pressure is next to the compressor on the aluminum pressure bottle mounted to the compressor. I am not a fan of running R134 in vintage compressors. The ac is cool but the pressure bottle and compressor get quite hot which seems wrong. any help is appreciated.


 Aluminum "pressure bottle" on compressor is the discharge side or the high side.It should have the fatter fitting with the red cap.

The large tube that comes out of the evaporator case that makes a U turn is the low pressure side.It should have the skinny longer fitting on it and the blue cap.

The system is known as POA system, or a pilot operated absolute system. I dont fully understand them as they were not used when I became a tech and I saw a few , so If I charged them and they worked , then OK.

The POA valve , the thing that has the low fitting on it and all the flats to put a wrench on it , also has an oil bleed line the goes to it from the expansion valve.

The system is designed to regulate flow of refrigerant to the evap , rather than cycle the compressor on or off.In fact it is designed so the compressor runs constantly without shutting off.

Here is a link that shows the POA valve differences.

https://originalair.com/restoration-gm-poa-valves

Now, that being said, take a few minutes and be sure that your fittings are on correctly, then hook up a gauge set and run the system 

Close the windows , turn the fan on medium and set it to recirculate. Be sure it is hot outside.Let it run 5-10minutes, then look at the gauges and write down the pressure readings.We will go from there . Also record the duct temperature

:grin2:


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## LATECH (Jul 18, 2018)

look at this picture here.

Palladium Silver 1969 GTO Hardtop - Ultimate Pontiac GTO Photo Detail

The big can on the compressor is part of the high side.The POA valve is clearly visible back at the evap case as is the fitting for r 12 , (which is the fitting for the low side -blue) on the r 134a refrigerant fitting.


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## 8222raspashillrd (Jul 22, 2018)

*thank you latech*



LATECH said:


> Aluminum "pressure bottle" on compressor is the discharge side or the high side.It should have the fatter fitting with the red cap.
> 
> The large tube that comes out of the evaporator case that makes a U turn is the low pressure side.It should have the skinny longer fitting on it and the blue cap.
> 
> ...


 thanks you have helped me greatly. the guy i bought the car from has the high pressure and low pressure fittings in reverse. i will remove them and install the correct low pressure and high pressure fittings in the correct location. I dont know if the system will discharge when there are removed but if so i can vacuum the system and recharge it. there are no labels on the system identifying what freon is in it. IS there any way to tell if R12 or 134?? if R134 then it has pag or esther oil if R12 mineral. I would like to recharge with R12 and not 134 but if i am not able to determin what gas is in they system i have to restart the system from scratch draining the oil with new dryer ect to install mineral oil for R12. 
Have you used any of the replacemnt freon blends sold stating they can be direct add to either systems??? It would resolve my problem of having to drain the oil and replace the dryer i could just vacuum the system for 30 min and recharge. There are good reviews on it the blended freon working well but negative posts on it also.

thank you so much for helping me. best regards, john


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## LATECH (Jul 18, 2018)

Use 134a. Period.

Chances are whoever "retrofitted " it (I use the term loosely) may or may not have put any oil in ,or could have dumped a buttload of oil in.

There in lies the problem. 

Most retrofits of that era ran an Esther oil. If you need to put some in (to be determined later) A synthetic esther is best as it mixes as well as you can expect with or Refrigerant oil,like say mineral oil.

Freon is a trade mark name used By Dow chemical company for its proprietary blend of chemicals that made up R 12.

Refrigerant is just that. Refrigerant. Freon is refrigerant. R134 a is refrigerant . 404a is refrigerant. See where I am going ?

Not busting chops, just clearing up a common misnomer, that's all.

Any way, probably best to get your fittings straight. You may or may not lose refrigerant by pulling them of.Some fittings are just like a little collar and are nothing more than an adapter , and the valve stays on the factory line. some fittings are such that you remove the factory valve and install the fitting, which has its own valve. The latter will let out the refrigerant if so removed. Just be mindful.

Once the fittings are corrected, put the gauges on and see what the pressures are by performing the AC performance test I outlined ealier. Post said results.


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## BearGFR (Aug 25, 2008)

LATECH said:


> .... lot's of good information from LATECH...


Please pardon the thread hijack. LATECH you obviously know your way around a/c systems so I hope you don't mind my dumb question here. My 69 is a factory a/c car, but when I built it in 2011 I opted to replace the system with an aftermarket one for a couple of reasons (what I thought then was the impossibility of getting r12, the fact that all the factory parts had been sitting open to the atmosphere for 20+ years waiting for me to get the car done, and the expectation that my engine build wasn't going to make sufficient vacuum to run the factory system). 

Had I realized at the time that the aftermarket systems don't have the capability of bringing in outside air, I might have reconsidered, but it's "too late now". 

I've never been happy with how the aftermarket r134a system performs - it just doesn't get cold enough nor does it move enough air volume, not for Texas anyway. But I think that recently I've figured out that I may have been over-charging it, thinking that the right thing was to try to get the low side pressure on the manifold gauges all the way to the upper limit of the range specified on a chart I have that recommends charging pressures based on ambient temperatures. 

Anyway, my real question has to do with refrigerant oil. The compressor was supplied with oil already in it when I bought it, but I've had the system open several times since I first installed it (always carefully evacuated before recharging), to the point now that I'm concerned that it may need oil. How do I tell how much is still present in the system and if so, how much to add?

Please feel free to comment on anything I've said, and O.P., I apologize again for hijacking your thread.

Bear


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## LATECH (Jul 18, 2018)

Bear,

Without knowing how much oil is in the system or if it has too much it can be a problem to get it right.

Knowing what you have in it is pretty rudimentary .But ,on a never opened new system, If you have evacuated the system with a machine, the machine can pull a few ounces out. So it is best to add , say maybe 2 ounces back in when recharging from repair .

Now if you have replaced a component , its best to add some for that as well. Replacing the accumulator, should require an additional 2 ounces. The evaporator, 1 ounce. The condenser 1-2 ounces. 

That being said, I use Synthetic PAG in anything I repair, uless it specifies POE (Poly Esther Olefin) which some OE s are.

When I assemble a system, I ALWAYS dump the oil out of the replacement compressor, and measure it in a measuring cup.

If all I am changing is the compressor and accumulator, then I put 2-3 ounces in the compressor, and dump 1 ounce in the accumulator.

Then assemble, rotate compressor by hand to help move any oil so it doesnt hydrolock, and then vacuum and charge.

Your problem could be a number of things.

It could be weak airflow across the condenser , but if that were the case the temp would improve with road speed(more airflow)
Does it?

Post what system you have so I can look it up and check the specs.Then we can go on from there.

Maybe create a new thread too>:smile3::smile3:


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## 8222raspashillrd (Jul 22, 2018)

Hello i have resolved my ac issue with all your help i want to thank everyone. 

I have another question. I upgraded my wifes 74 vett with a later model GM blower motor which increased airflow through the duct work substantially. My GTO blower does not put out much airflow like the C3 vettes. Has anyone upgraded their blower motor to a more efficient blower motor to increase air flow?


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