Automotive Air Conditioning Information Forum (Archives)

71GTO on Mon May 21, 2012 6:16 AM

Year: 1971
Make: Pontiac
Model: GTO
Engine Size: 455
Refrigerant Type: 134a
Ambient Temp: 80
Pressure Low: 22
Pressure High: 400
Country of Origin: United States

Hi all. I originally posted this in the wrong place. Sorry about the re-post.

I have very little experience and I can't find anyone locally to work on my stuff so here we go. It's in a 71 GTO but the only thing original is the evaporator. I have the new POA update with the cycle switch, new expansion valve, rebuilt sanden 508, universal condenser 14-1/4 in x 25 in, and a hose and drier kit from Southern Rods.com. The condenser is mounted about three inches infront of the radiator with a transmission cooler in front of the condenser. Along with a 18" puller fan behind the radiator, I have 2 10" pusher fans. One directly on the transmission cooler and one on the condenser. I put 8 oz. of PAG 100 in, pulled a vacuum for a couple of hours. Made sure there wasn't a leak for a couple of hours and tried filling with 134a. Before emptying even one can the low climbs to low 20 but the high side starts climbing up to 350, 400. I shut it down at this point. I thought it might be my evaporator since it is the only thing that is not new. I took it out and flushed it and made it and it's liquid bleed line were clear. When I took it out, it had alot of oil in it. I do wish I had measure how much was in there. While I had it apart, I blew air through the condenser, drier, expansion valve, and line to make sure they weren't plugged. Dumped out the compressor and put in approx. 4 ounces in it so it was the right level on the dipstick. Pulled another vacuum, started charging with the same symptoms. I sprayed cold water on the condenser with no high side change.
Please Help. The only thing I can this of is to replace the drier and try again before I give on A/C in this car.

ps. the drier I have now doesn't have a sight glass.

JJM on Tue May 22, 2012 1:37 AM

This is why I don't like modding. Better off keeping it all factory.

Not sure an oil bleed line is even necessary with the POA gone. Is the replacement expansion valve is internally (one capillary tube) or externally equalized (two capillary tubes, the second connected to the POA). If you went with a POA eliminator, you probably have to go with an internally equalized valve.

Have you tested the new expansion valve?

Are you sure the receiver dryer is plumbed correctly?

How much heat is the tranny cooler dumping onto the condenser?

Are both fans operating in the right direction? Nothing worked as good as the original fan with a thermostatic clutch, and original shrouding.

Too many variables with a modded system...

Joe

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

bohica2xo on Tue May 22, 2012 3:11 AM

400 on the high side with 12 ounces in the system sounds like a blocked condensor. Why type of condensor is it?

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

71GTO on Tue May 22, 2012 5:00 PM

Thanks for the replies.
As far as the questions, the drier is plumbed the correct direction. Both pusher fans are pushing the correct way. I don't know what temp the tranny cooler is inducing but I would have a hard time thinking it is making any heat with the problem I am having because I am starting with a cold car and the system is making the 400 psi within 30 secs. The condenser is brand new and I have blow through it and it didn't seemed blocked. Could it still have a blockage and still get air through? Oil is collecting in the evaporator and I mean alot of oil. I only have 8oz in the system, when I break it apart again I will have to measure it. The bleed line on the evaporator is to route excess oil out of the evaporator right? When I first started, I have it blocked off because I didn't think it was needed but had the same problem. So I plumbed it in. I thought that might have been my problem is a blockage in that because of all the oil collecting in the evaporator. The expansion valve is external with the bulb on the suction side of the evaporator and the other tube on the updated tube. The only testing I have done with the valve is making sure it wasn't blocked. What other testing can I do? Is it suppose to atomize the oil so it shouldn't collect in the evap? If an internal regulated valve could help, I will definitely replace it.

Thanks J

mk378 on Tue May 22, 2012 5:52 PM

Is condenser plumbed properly-- in at the top out at the bottom? If there are isolation valves on the compressor fittings, are they open?

I think the oil bleed line is just to keep oil from building up behind the POA valve, ordinary TXV systems don't have one. Like JJM said, don't confuse it with a TXV equalizing line though.

Make sure the system has a HPCO switch, even with "normal" operation with the airflow setup you have it's likely to be needed.

Edited: Tue May 22, 2012 at 5:55 PM by mk378

71GTO on Tue May 22, 2012 6:05 PM

Quote
Is condenser plumbed properly-- in at the top out at the bottom? If there are isolation valves on the compressor fittings, are they open?

Yeah, It's plumbed in correctly. In at the top. I don't have a hpco switch in but I'll but one on. I see that everyone is pointing to the condenser, either not enough air flow or blockage. I completely understand that but why is the evaporator getting oil logged? Is that normal? I have a picture in my head on what is going on and it's hard to look past that.

Quote
If there are isolation valves on the compressor fittings, are they open?

It's a sanden 508. I don't believe there are valves on it, at least none that I see.


In my original post I mentioned that the condenser has about 21/2 to 3 inches between it and the radiator. With the 2 10" pusher fans is that still an issue? I did spray the condenser with cold water while it was building pressure with zero drop in pressure.

One last thought. If the drier was saturated, would that be causing any of my problems or would that long vacuums I've put on the system take care of that?

J-

mk378 on Tue May 22, 2012 6:24 PM

I thought you said it was a new drier. Don't use NOS driers, they may not be compatible with R-134a. Prolonged vacuum will not change anything, there is no way to remove water from a drier. It's an expendable part like an oil filter.

Edited: Tue May 22, 2012 at 6:28 PM by mk378

71GTO on Tue May 22, 2012 6:30 PM

Quote
I thought you said it was a new drier. Don't use NOS driers, they may not be compatible with R-134a.

Yes it is a new drier that was part of a hose kit from Southern hot rods made for 134a. The drier came capped off of course and I've had the system open twice for very short periods of time. I taped off the hoses both times.

J-

JJM on Tue May 22, 2012 8:31 PM

Is the dryer new? If not, absolutely replace it. It's like doing an engine rebuild and using and old oil filter. And MK378 makes a good point about NOS dryers, aside from the desiccant incompatibility, they're also dried up (no pun intended) from age. They can actually damage system. If you wanted the OEM "look" better off cutting one open and replacing the desiccant bag.

Something is way restricted on the high side. Where are the high and low side ports located, so we can get an idea of possible restriction points?

I also think an externally equalized TXV (one with an extra line leading to the POA) could be troublesome with a POA eliminator.

Lots of oil typically does collect in the evaporator. The oil bypass probably isn't helping in the absence of a POA though.

Posting pics would probably be helpful at this point.

Joe

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

mk378 on Tue May 22, 2012 9:35 PM

You count on good refrigerant flow to blow the oil out of the evaporator, not going to happen when undercharged. External compensated TXV must have the compensator line connected to the low side after the evaporator. Make sure flow through TXV is in the proper direction, most have an arrow on them. If the two main ports are different sizes, the smaller one would be the inlet.

Edited: Tue May 22, 2012 at 9:36 PM by mk378

71GTO on Tue May 22, 2012 9:55 PM

Hopefully those images will show up. I took a picture of the system as a whole, upclose of the POA update. You'll notice a flex line with convoluted tubing covering it going into the POA update. That's the liquid bleed line. It was originally cut. I spliced it with a flex line. It is sealed, hold a vacuum, and is not plugged. The other 2 pictures is of the condenser both sides. It's not a very good view but you can see one pusher fan on the left and another ontop of the tranny cooler on the right.

Quote
Is the dryer new? If not, absolutely replace it. It's like doing an engine rebuild and using and old oil filter. And MK378 makes a good point about NOS dryers, aside from the desiccant incompatibility, they're also dried up (no pun intended) from age. They can actually damage system. If you wanted the OEM "look" better off cutting one open and replacing the desiccant bag.

It is a new drier and I'm ordering a binary switch to put on it tonight.

Quote
Something is way restricted on the high side. Where are the high and low side ports located, so we can get an idea of possible restriction points?

In one picture you can see the high and low ports that I am using is on the 90's going into the pump. there is another low side on the POA update, but I do not use it. One thought on the restriction. Is there a way I can flow test the condenser. I can push air through it no problem, but would it be worth trying to pump a certain PSI into it and read what comes out?

Quote
I also think an externally equalized TXV (one with an extra line leading to the POA) could be troublesome with a POA eliminator. Lots of oil typically does collect in the evaporator. The oil bypass probably isn't helping in the absence of a POA though.

I am open to putting an internal TXV on. I thought that this POA update kit was common practice for this era GM systems?






Edited: Tue May 22, 2012 at 10:15 PM by 71GTO

71GTO on Tue May 22, 2012 9:56 PM

Yeah, sorry about the size of the pictures. But you should be able to see everyting

Jason

Edited: Tue May 22, 2012 at 10:16 PM by 71GTO

mk378 on Tue May 22, 2012 11:40 PM

The fans are a problem. The blades are curved the wrong way. That type of blade is designed to operate in one direction only, moving air from the open side (shallow angle, slow moving air) to the motor side (steep angle, fast moving air). You can't just run them backwards, for "pusher" service, they will be very inefficient. Also they're too small.

The "POA Update" should only be installed when you can't get a real POA valve. The original system was superior. Without a POA valve, I would use evaporator temperature control like most TXV cars do. The pressure control tends to cause a lot of cycling of the compressor. But that is an issue for the future, there are bigger problems now.


Edited: Tue May 22, 2012 at 11:51 PM by mk378

71GTO on Wed May 23, 2012 11:56 AM

Quote
User is offline The fans are a problem. The blades are curved the wrong way. That type of blade is designed to operate in one direction only, moving air from the open side (shallow angle, slow moving air) to the motor side (steep angle, fast moving air). You can't just run them backwards, for "pusher" service, they will be very inefficient. Also they're too small.

Absolutely right about the fans pushing air the wrong way. I forgot to take the blades off the motor and reverse them. Thanks for pointing that out. About being to small, I must have forgot to mention that I also have an 18" Fan on the radiator with a very good sealing shroud. It moves alot of air. I know that the condenser is alittle far off the radiator that's why I put the pushers on there. I would think that would be enough air wouldn't it?

Quote
The "POA Update" should only be installed when you can't get a real POA valve. The original system was superior. Without a POA valve

That is why I got the update kit is because I couldn't find a good POA valve for a reasonable price and I thought update would get the job done. I have read mix review on the update. Some say it has worked great and other say it's a boat anchor. The question for me is it functional "for now". If I can get the system up and running and it's just not as efficient as the original I can replace it, but if it just won't work and is causing my problem I can address it now. First, before I spend another 100 to 150 I would like to just see cool air coming out of my vents.


Quote
TextI would use evaporator temperature control like most TXV cars do

I am ordering an internally controlled valve now.


Quote
400 on the high side with 12 ounces in the system sounds like a blocked condensor. Why type of condensor is it?

It's a Parallel Flow 14.5"x25"

Quote
You count on good refrigerant flow to blow the oil out of the evaporator, not going to happen when undercharged

Question about this is my situation. I am filling the system with the 12 oz cans. How do I get enough refrigerant in the system to push the oil out of the evaporator. I can't even get one can in before my high side is in the danger zone. I feel that this is my restriction in the system is the evaporator getting oil logged.

Thanks everyone for being patient with my noobie ways and my hacked a/c system. I'm sure we can get it working.

Jason

Edited: Wed May 23, 2012 at 6:21 PM by 71GTO

JJM on Wed May 23, 2012 8:37 PM

Really nice catch MK378! I would've never caught that from the pics.

I would leave the fan off for now and retest the system, post some readings for us, and see what kind of performance you're looking at. I wouldn't replace the TXV just yet, but if you are going to open the system, as MK378 mentioned the original POA setup is the best bet.

For a "hacked up" system, it is done pretty nice I have to say. Nice OEM style crimps on the lines and all.

Joe

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

bohica2xo on Thu May 24, 2012 1:05 PM

Ok, 400 psi on 12 ounces of refrigerant with water sprayed on the condensor?

Yeah, something is blocked. Perhaps a manufacturing defect when the condensor was brazed together, or a bad dryer.

Your dryer does have a sightglass. Right next to the stamping that says "IN" is a round spot. It is a masking disc stuck down on the glass window before paint. Peel it off with a thumbnail. Run the system (briefly) and tell us what you see there.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

71GTO on Thu May 24, 2012 5:28 PM

Quote
Your dryer does have a sightglass. Right next to the stamping that says "IN" is a round spot. It is a masking disc stuck down on the glass window before paint. Peel it off with a thumbnail. Run the system (briefly) and tell us what you see there.

Thanks for the tip. Didn't even occur to me that was taped up for painting.. In the sight glass I see fine clear bubbles spirting up. Also the inlet to the evaporator downstream from the expansion valve starts to get cold on initial start up the the high side builds through the roof. That is still with the 1/2 to 3/4 of a 12 oz can.

Jason

mk378 on Thu May 24, 2012 9:05 PM

It really seems like the condenser isn't doing anything at all. Is the refrigerant really going through the tubes, or does it just short circuit from the inlet to the outlet? The entire condenser should be getting too hot to touch with that high a pressure. Feel the tube header on the other side. I think you have it upside down, the largest group of tubes is usually at the top of a parallel flow. But I wouldn't think that's that big of a difference.

Edited: Thu May 24, 2012 at 9:07 PM by mk378

71GTO on Wed June 06, 2012 8:57 PM

I've taken some time before replying to all your suggestions until I made some changes and tried it again. So here's the update. I've moved the condenser closer to the radiator and sealed it to the radiator so that all the air being pulled has to go through the condenser. I changed the expansion valve from the pressure regulated to the internal. Switched the blades of the 2 pusher fans around and put a high side cutout switch on the side of the drier.

It has finally taken more than 1/2 can of refrigerant. Right now I got a can and a half in it. The bottom of the expansion valve is frosting up, I still see bubbles in the drier but I stopped filling because I am confused about something. Everything seems to be working (given the low charge) but my high side is still high. While I was filling, my low side was around 25lbs. and my high side around 350lbs.. I felt the condenser and the inlet at the top is hot to the touch and the bottom is just warm, so it seems like it's doing it's job. I kicked the compressor off for a 30 secs and kicked it back on and the pressure on the gauge shot immediately to 450lbs +. (the pressure comes down if you let it but I wasn't comfortable with that high of pressure). The funny thing is the high level cutout switch didn't turn the compressor off. I'm not sure what it's rated at but I'm sure it's below 450 to 500lbs. (it is wired in series with the cycle switch from the suction side). My one question about this is, my high side port is directly on the 90 coming out of the compressor and the high side switch is on the drier past the condenser. Do you have a pressure drop across the condenser or does this mean the condenser is plugged?

This is my last go around before I ditch the idea of having a/c in this car. Any last opinions or ideas will be greatly appreciated.

Thanks J

71GTO on Sun July 08, 2012 7:51 PM

New Update-
I have replaced the condenser with another parallel flow 15x25. Replaced the drier and put on a hpco switch on the drier. I took the 2 pusher fans off the front and put them behind as pullers with the 18" puller. So now I have an 18" puller and 2 8" puller fans with a darn near air tight shroud. ( oh, and removed the transmission cooler, so there is nothing in front of the condenser). And replaced the expansion valve with the internal type. Pulled vacuum for 1/2 hr and charged with about 2lbs. High and lows are at 300 and 49. It's 85 degrees out with 75% humidity.

The condenser inlet is 168.3 degrees outlet is 91.2 degrees. The evap outlet is 96 degrees and the inlet I have wrapped in cork tape so I don't know the temp, but it was frosting.

My problems: 75 degree vent temp
my compressor makes a high pitched bearing sound at exactly 200 rpm and up and stops as soon as it drops below 2000rpm. it doesn't die down and stop, it just stops.(this is a rebuilt sanden 508.)

Does this sound like an airflow problem through the evaporator? I did clean the evaporator fins before putting it back in way back when.

I thought I would ask before I start tearing the heater box apart.

Thanks J

bohica2xo on Mon July 09, 2012 2:59 PM

Does not look like an evaporator problem.

But the pressures & temps don't add up. 49 psi on the low side with 75f vent temps would be a capacity or charge issue - but then you say you have 96f temps on the suction side of the evaporator.

A rebuilt 508? Could be part of the problem, especially if it has odd noises.

You gave up a 12 cid / rev compressor for the sanden - a third less displacement. The sanden can only move so much volume, and it needs to spin faster than the A6 to even get close. Try to get the compressor shaft speed up over 4000 rpm, and add some charge.

You will always have 30% less cooling capacity than the stock A6 with that sanden compressor.

B

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

JJM on Mon July 09, 2012 7:40 PM

Where are you getting your parts from?

If the evaporator inlet is frosting and the outlet is 96F, it sounds like your (new) TXV is bad or the evaporator is plugged. Have you tested the valve by shocking it with cold and hot and seeing if it responds?

The evaporator inlet typically is not insulated, only the outlet where the sensing bulb goes.

In my opinion, you would be far better off with a POA and TXV. Even with the compressor and lines not OEM, the system would probably cool very well. These systems were flawless when original.

Joe

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

71GTO on Tue July 10, 2012 6:45 AM

I got my condenser, drier, and expansion valve from nostalgic air parts. I insulated the bottom part of the evaporator because I thought it might be absorbing some heat from the headers right beside it. Didn't know if it would matter or not.
you have me convinced about the poa valve. I am on the lookout for a poa valve at a reasonable price.
You mentioned my evaporator might be plugged? Any way to check that? What temp should the suction side of the evaporator be?

Last question for the moment- does anyone know of a stronger blower option for GM a-bodies like my 1971 GTO. Even on high, it's seems weak.

Thanks for your guy's patience. I know this threads been drawn out.

J

bohica2xo on Tue July 10, 2012 11:21 AM

I still want to know how you get 75f vent temps with a 96f reading on the suction line at the evaporator.

How does the refrigerant become 21 degrees warmer than the air moving over it inside the evaporator case?

.



-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

71GTO on Wed July 11, 2012 12:27 AM

Quote
How does the refrigerant become 21 degrees warmer than the air moving over it inside the evaporator case?

I took the reading with an IR thermometer on the suction side of the evap. I may have picked up some engine heat? That would be the only thing I would think of.

Quote
Have you tested the valve by shocking it with cold and hot and seeing if it responds?

I didn't test the valve in hand with hot and cold. Just pulled it new out of the box and threw it on. Would it be worth trying to put it in hot water while in the system to see if my vent temps come down?