Need help with A/C
Thread Starter
Pro
Joined: Jun 2005
Posts: 552
Likes: 2
From: Waynesboro GA
Need help with A/C
I am trying to get the A/C on my 81 to cool. The previous owner said he replaced all he components. The condensor looks like it may be the original. The rest obviously looks new. This is my second summer fighting with this system. It had a leak, and I fixed it. It had been converted to R-134 along with the new parts. The problem I am having, the High Side is freezing up on the evaporator side of the orfice. I replaced the orfice today for the second time. The the best I have ever been able to get is "cool". The pressures with 1 can of R-134 is 35 Low Side, 200-225 High Side. This is after 15 minutes at over idle to get the gas in...
Anyone got any ideas?? Sounds like a blockage but pressures are about what a full charge shoudl be??? Help! Black Corvette in S Georgia in July with NO A/C is unusable...
Anyone got any ideas?? Sounds like a blockage but pressures are about what a full charge shoudl be??? Help! Black Corvette in S Georgia in July with NO A/C is unusable...
Racer
Joined: Dec 2005
Posts: 325
Likes: 0
From: Partlow VA
Good leak check. With only one can of 134a the high side appears to be a running high. Check the air flow over the condenser. If possible use a garden hose with a nozzle that will produce a fine mist and spray it over the front of condenser and what the gauges. Sounds like not enough heat is being removed by the condenser and with that head pressure the system would appear to be full.
Thread Starter
Pro
Joined: Jun 2005
Posts: 552
Likes: 2
From: Waynesboro GA
I know I am getting good flow over the evaporator. The hose idea is worth a try. Is this normal to get one to charge? Back in my earlier years seems like on freshly vacuumed system the R12 would just be itching to get in..I will try the hose tommorrow. Think there could be a blockage in the dryer?? The low side hoses coming out of the evaporator never get cool..Thanks for all your help! This thing is about to make me sell the car..
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
If you didn't do the original work. You may have too much oil in system instead of freon. After you fixed any leak you should always replace the acummulator/filter. The desiccant goes bad. With a proper vacumn, 134a should go in the same as r12. Another sign that you may have too much oil or not vacumned enough. With those pressures, you should be getting around 50° at the ducts in these temperatures.
Only way is to take system apart flush completely, reassemble, vacumn and put correct amount and type of oil in.
To make 134a work properly, and it will, change out the condenser to a parallel flow and add a condenser pusher fan even though it has an additional elec fan. Most people sadly cheap out at this.
Only way is to take system apart flush completely, reassemble, vacumn and put correct amount and type of oil in.
To make 134a work properly, and it will, change out the condenser to a parallel flow and add a condenser pusher fan even though it has an additional elec fan. Most people sadly cheap out at this.
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Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
You buy them at any auto a/c distributer or on the net. All new cars use them. If using a used one flush it properly. You may have to get new fittings crimped on your hoses. No other changes necessary
They will work with your existing evap.
Look at a Caravan (lots of them around). They look more like regular radiator fins than the old tube type fins for r12. The btu/hr rating is a lot more and that is why 134a will work well.
It's probably the single best change that auto manufacturers did to make 134a work as well as r12
Batman:
I see you have a 77, I have to do the a/c on a 77 with the a6 compressor in the next few weeks, so I'll let you know what parts are required.
They will work with your existing evap.
Look at a Caravan (lots of them around). They look more like regular radiator fins than the old tube type fins for r12. The btu/hr rating is a lot more and that is why 134a will work well.
It's probably the single best change that auto manufacturers did to make 134a work as well as r12
Batman:
I see you have a 77, I have to do the a/c on a 77 with the a6 compressor in the next few weeks, so I'll let you know what parts are required.
Melting Slicks
Joined: Dec 2000
Posts: 3,407
Likes: 2
From: Carmichael CA
If you are getting frost on the line going into the evaporator then your refrigerant system is working fine. Your problem is getting air to flow through the evaporator in order to prevent its inlet line from freezing up. I discovered that a new motor would give me 30% more air flow OR moving the blower motor supply wire from the 11.5V ignition fuse terminal to the 13.5V alternator output post would also give me 30% more air flow; and, if both a new motor AND moving the wire to the 13.5V terminal results in a 90% increase in air flow.
Drifting
Joined: May 2005
Posts: 1,629
Likes: 4
From: Somers CT
My system is older and slightly different than yours but I'll throw this out anyway:
I was having the same problem with R12 and noticed that the airflow was reduced from the vents along with the lines freezing as you've indicated. Turns out, in my system anyway, the POA valve was sticking allowing the evaporator to freeze up. The POA valve allows a small amount of freon from the low side to filter back to the high side to keep it from freezing. When I fixed the valve the lines stopped freezing and the A/C started working fine.
These guys were very helpful to me when I asked for help.
http://acsource.net/acforum/viewforum.php?f=1
Bill
I was having the same problem with R12 and noticed that the airflow was reduced from the vents along with the lines freezing as you've indicated. Turns out, in my system anyway, the POA valve was sticking allowing the evaporator to freeze up. The POA valve allows a small amount of freon from the low side to filter back to the high side to keep it from freezing. When I fixed the valve the lines stopped freezing and the A/C started working fine.
These guys were very helpful to me when I asked for help.
http://acsource.net/acforum/viewforum.php?f=1
Bill
Team Owner
Joined: Oct 2004
Posts: 23,831
Likes: 10
From: Springfield MO
St. Jude Donor '07
noonie, I appreciate it. Interesting that you mentioned a 77 with the A6 - my car has an R4. It's very early production (around #2500), but I don't have a clue if it's original.
Melting Slicks
Joined: Dec 2000
Posts: 3,407
Likes: 2
From: Carmichael CA
Originally Posted by TopGunn
My system is older and slightly different than yours but I'll throw this out anyway:
I was having the same problem with R12 and noticed that the airflow was reduced from the vents along with the lines freezing as you've indicated. Turns out, in my system anyway, the POA valve was sticking allowing the evaporator to freeze up. The POA valve allows a small amount of freon from the low side to filter back to the high side to keep it from freezing. When I fixed the valve the lines stopped freezing and the A/C started working fine.
These guys were very helpful to me when I asked for help.
http://acsource.net/acforum/viewforum.php?f=1
Bill
I was having the same problem with R12 and noticed that the airflow was reduced from the vents along with the lines freezing as you've indicated. Turns out, in my system anyway, the POA valve was sticking allowing the evaporator to freeze up. The POA valve allows a small amount of freon from the low side to filter back to the high side to keep it from freezing. When I fixed the valve the lines stopped freezing and the A/C started working fine.
These guys were very helpful to me when I asked for help.
http://acsource.net/acforum/viewforum.php?f=1
Bill
Drifting
Joined: May 2005
Posts: 1,629
Likes: 4
From: Somers CT
Originally Posted by Rockn-Roll
Ah...that's interesting. I had the same problem, but with a new POA valve. I've finally opened up the air box and I found that it was 1/3 full of leaves. Apparently a stuck POA valve will result in the same symptoms as an evaporator plugged up with leaves. After replacing the POA valve and clearing out the air box...I'm thinking that clearing out the air box is a LOT easier and of course cheaper since it's free. It may not fix the problem if it really is a stuck POA valve, but if the air box hasn't been checked in like 30 years then there may be some benefit from cleaning it out.
Thread Starter
Pro
Joined: Jun 2005
Posts: 552
Likes: 2
From: Waynesboro GA
Thanks a million for all the answers. I hope one will work. Lucked up today at the local parts store and found a new dryer. I am going to try that and see if that could be the problem. I had the whole dash out, and all the ducts seem to be working fine, the heater control valve is working. Going to try the dryer...Thanks again, please post if you think of anything else!
Thread Starter
Pro
Joined: Jun 2005
Posts: 552
Likes: 2
From: Waynesboro GA
Originally Posted by Rockn-Roll
If you are getting frost on the line going into the evaporator then your refrigerant system is working fine. Your problem is getting air to flow through the evaporator in order to prevent its inlet line from freezing up. I discovered that a new motor would give me 30% more air flow OR moving the blower motor supply wire from the 11.5V ignition fuse terminal to the 13.5V alternator output post would also give me 30% more air flow; and, if both a new motor AND moving the wire to the 13.5V terminal results in a 90% increase in air flow.
Melting Slicks
Joined: May 2002
Posts: 2,717
Likes: 121
From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
What brand service gauges are you using? I have seen service gauges that have a shradder vavle in the end of the center hose, there is an adapter that screws onto the end of this hose to allow you to charge and pull a vacuum. The gague manifold has fittings were the hoses attach for storage so they do not hange loose, this adapter will sometimes stay attached to the manifold and you may not reallize it. not sure if this is the problem or not, just throwing sugestions out there. Really sounds like there is still moister in the system. At 35 psig the coil temp is at 40 deg, this is not cold enough to cause freezing. To much oil is also a possability the system should have aprox 6 to 7 oz of oil, 2 oz in the evap, 2 oz in the condensor and 2 to 3 oz in the comp.
Neal
PS: this is what my evap looked like when I pulled it out.
Neal
PS: this is what my evap looked like when I pulled it out.
Last edited by chevymans 77; Jul 18, 2006 at 11:13 PM.