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70 cadillac pressures

70goldcaddy on Mon July 16, 2012 10:43 PM User is offline

Year: 1970
Make: Cadillac
Model: sedan deville
Engine Size: 472
Refrigerant Type: r134a
Ambient Temp: 80
Pressure Low: 20
Pressure High: 200
Country of Origin: Canada

New compressor, expansion valve, drier
installed charged with r134a installed and charged at dealer
cools ok but could be better. I'm not sure how many lbs went in.
parked i'm able to rev the engine and bring the low side down to 10 psi, high didn't go beyond 225psi.
idling the low side hit 26 psi.
My understanding of this system with the POA valve is that the low side shouldn't fluctuate that much.
valve may be stuck?

long road trips in cooler temps(60-70F) tends to freeze of evaporator even though it doesn't cool very good past 75f.
thanks for the advice

elev. 2100 feet

JJM on Wed July 18, 2012 11:37 PM User is offline

System is likely undercharged, or possibly the TXV is bad. It also appears the POA might be stuck.


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70goldcaddy on Mon August 06, 2012 11:44 PM User is offline

so today out driving at 86f 20% hum
vent temp on recir got down to 50f

So it's somewhat possible that a system could have moderate cooling at 80-90 but freeze off the evap at 60-65 because low charge. or has there got to be another problem

chris142 on Sat August 11, 2012 5:09 PM User is offline

Those older GM cars did some strange things with R134a in them. I'd put it back to R12 and see what it does.

JJM on Sat August 11, 2012 7:59 PM User is offline

The evaporator should not be freezing - that's what the POA is supposed to prevent if the system is functioning properly - does the suction line ice up?

The low side should not be coming down to 10 PSI unless the expansion valve is bad (new doesn't mean good) or the system is severely undercharged. To test the expansion valve, carefully remove the sensing bulb from the evaporator outlet pipe, making sure not to kink or otherwise damage the capillary tube. Prepare a container of crushed ice and water (32ºF), and another container of hot water (approximately 125º or more). Start the engine and run it at 2,000 RPM, and record your pressures with the air-conditioning on. At this point your low side will be high. Immerse the sensing bulb in the container of ice water, and the low side pressure should drop. Immerse the sensing bulb in the container of hot water, and the low side pressure should rise. If the pressures do not change, or change very little, the expansion valve is defective and must be replaced.

During the ice water portion of this test, you should be able to hear and feel the POA "throttling" in attempt to keep the low pressure up.


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NickD on Mon August 13, 2012 10:19 AM User is offline

Still selling and using R-12 in China, Mexico, and practically all Latin American countries where it really gets hot. Just don't try to bring a can of R-12 back, punishment is worse than trying to smuggle in crack.

Canada that may only get one or two hot days a year, and that is only during mid-day, gets rather cool or even cold at night completely banned R-12. Okay if you still have it, but illegal even to add one or two ounces to top it off. You have to convert to environmentally friendly R-134a, so telling the OP to switch back to R-12 is against their law. Still can buy and use it in the USA if you are willing to pay the price, but since its use is diminishing after close to twenty years and the price of R-134a is skyrocketing. In the USA, really doesn't pay to convert.

We should be pleased that Canada is interested in protecting the ozone layer where practically any other country in the western hemisphere is not.

Was R-12 really harming the ozone layer, even our NASA backed off of that theory from a couple of crack pots trying to make a name for themselves at UCRA. Hey, they were educated in this country!

Shouldn't even have to buy a can of R-12, according to our government, our atmosphere is loaded with it, just gather some up. But you won't find any, is completely biodegradable, UV radiation breaks it up, the chlorine can not exist in its natural state. On the other hand, HFC's don't have this characteristic and now is blamed for global warming. Methane natually released was and still is the leading cause of ozone depletion. Other scientist are saying solar flares from the sun in a 25 year cycle is causing global warming.

But the bottom line is that governments can't tax solar flares or natural methane emissions. But they can tax a can of R-12 or R-134a.

70goldcaddy on Mon August 20, 2012 12:19 AM User is offline

It was two years ago when I drove for an extended period in conditions that caused it to ice up. So I don't remember if the POA/suction line had frost.
currently this year it has not, just condensation but the expansion valve and fitting of the high side line will. water does run out of the evaporator when parked not as much as before though. As for switching back to r12, I won't bother. my research on here and other places tells me the 134 can be made to work. Vent temp wise i'm not far off and i haven't even adjusted anything yet.
high pressure side will be high with expansion valve stuck closed?

JJM on Sun August 26, 2012 4:40 PM User is offline

If the expansion valve and or liquid line is frosting, they're restricted.

I also don't see the point switching from one banned refrigerant to another refrigerant that's soon to be banned. Might as well stick to what the vehicle was designed for - though it does appear there's a malfunction.


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70goldcaddy on Tue August 28, 2012 9:33 PM User is offline

So I went to edmonton for a wedding. Driving about 375 miles one way. It was cool on the drive down 65-70 f. A/c worked good lots of frost on poa valve some at compressor on the low side. One the way back a little warmer 75 f, Ice build up on poa valve and suction side all way to the compressor, but almost no cooling.

Now the POA valve is almost stuck closed?

70goldcaddy on Wed August 29, 2012 12:19 AM User is offline

it gets cold very quickly on the low side all the way to the compressor. Earlier in the summer when it was working decent but not great I had no frost at all.

70goldcaddy on Thu August 30, 2012 9:59 PM User is offline

just thinking out loud here. I haven't got to borrow any gauges again but lets discuss the posibilities.

I have read other posts. where the frosting starts half way across the poa valve. mine is getting colder accross it but it is cold out of the evap. but no cooling.

So is the expansion valve stuck open, and i'm getting pressure drop across the restriction of traveling through the evap. but not accross the txv?
I'm not sure if the POA is working or not, but if the txv is stuck open the Poa should be wide open to try and dump pressure right?

In the off season I need to fix oil leaks and manifold leaks, an evacuate may be neccesary.
and i need to set/test the poa for 134a, well it's apart, and check out the txv.
What kind fitting do these system have? Are they JIC or SAE? Or special AC specific thread. just so i can cap the system.

JJM on Sat September 01, 2012 12:57 PM User is offline

Still haven't heard anything back on the TVX test, which can be done with the system closed and charged.

If in doubt, just throw in a new TXV, POA, and receiver dryer and be done with it.


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70goldcaddy on Sat September 01, 2012 9:10 PM User is offline

I put the sensing bulb in hot water, didn't change anything. But that would make it open more anyway. I beleive to have the opposite problem.
There is no frost on the txv or liquid line.

I will try some cold before I tear it down, maybe some anti-freeze that has been in the freezer.

What do you know about the new refridgerent coming out?

70goldcaddy on Mon September 03, 2012 10:22 PM User is offline

My reman is appears to be flinging oil. Don't know right now if it is loosing Refrigrent.

Are Brand New Four Seaons compressors bad as well?
Does the por6ten/s6 have the same displacement as the A6?

Where is the best place to buy an expansion valve and new drier for this unit.
What about hoses?
I see no listings for it on here on Arizona Mobile Air

Edited: Mon September 03, 2012 at 10:51 PM by 70goldcaddy

JJM on Thu September 06, 2012 9:17 PM User is offline

If you're not getting any response temperature shocking the TXV, it's probably bad. It could be restricted at the inlet - which would indicate other problems - or the sensing bulb has lost it's charge (I think they were charged with R-113 or R-114 back then). Any damage to the capillary tube?

Replace the TXV and receiver dryer, preferable with a GM part. Don't go with NOS on the dryer, as age kills the desiccant and it's probably not compatible with R-134a anyway.

New refrigerant? We're discussing it another thread if you're interested:


When considering your next auto A/C purchase, please consider the site that supports you:

JJM on Thu September 06, 2012 9:30 PM User is offline

Forgot the thread:

Scroll down a little further when we get into HFO-1234yf discussion somehow.

Wouldn't surprise me if a brand new Four Seizings compressor is bad. If it's flinging oil though, it's probably just the shaft seal, which is cheap to replace. The seal and tools are available from this site. You might also want to e-mail the site sponsor Tim on parts, he might be able to get them even though they're not listed. He may also be able to fabricate the hoses too.

I wouldn't replace that nice A6 with some aftermarket unit, but that's just me. Keep that nice Caddy and original as possible. Besides, I just can't see that ugly thing on that nice big 472. If this car is show quality or you want to keep as close to original as possible, give Classic Auto Air a try. They repair OEM A/C parts and make them look like new too.


When considering your next auto A/C purchase, please consider the site that supports you:

70goldcaddy on Sat September 08, 2012 11:14 PM User is offline

i'm not sure where my reman compressor was done. I bought it on ebay from OEair out of arizona I believe.

What if I can't buy a 134a txv from GM? I haven't tried but systems with txv never used 134a right?
Or is that part any different from an r12 unit.

My gm dealer laughs about looking for stuff that old. The computer doesn't go back that far. How much newer can I ask for to get the same part?

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