L@@K! Another AC question??

keithbkeller · keithbkeller's Garage

I did a ac update to my 81 911 SC Targa to a Chinese Sanden type compressor with new barrier hoses and replaced my rear condenser and put a new recv/dryer on it. Now I have vacuumed it and recharged it with 48 oz of 134r refrigerant and am getting cool ac but not cold. I have 32 psi in the low side and 30 psi at the high side at 1600 rpm with the rear engine cover up. When I close it and take it out for a drive on a 81 degree F day, I am seeing 55f on my thermometer inside the front vent. So here is my question: Why is my high side pressure so low and my low side so high? And then the 2nd part of my question; Why is it working at all if the pressures are so screwed up? This compressor only has the little air nozzles on it (see picture)and they are the same size. Take a look and see what you think? Also the high side tube sweats cold condensation and the compressor runs smooth. Thanks! http://forums.pelicanparts.com/ultimate/confused.gif

Arne2 · Arne2's Garage

Can't check pressures accurately with the hood up. Close it down, maybe with some towels se seal the edges. You need airflow through the deckled condenser.

wwest · wwest's Garage

Quote:

Originally Posted by Arne2

Can't check pressures accurately with the hood up. Close it down, maybe with some towels se seal the edges. You need airflow through the deckled condenser.

Hood up, poor condenser airflow would result in extraordinary high side pressures.

wwest · wwest's Garage

Quote:

Originally Posted by keithbkeller

I did a ac update to my 81 911 SC Targa to a Chinese Sanden type compressor with new barrier hoses and replaced my rear condenser and put a new recv/dryer on it. Now I have vacuumed it and recharged it with 48 oz of 134r refrigerant and am getting cool ac but not cold. I have 32 psi in the low side and 30 psi at the high side at 1600 rpm with the rear engine cover up. When I close it and take it out for a drive on a 81 degree F day, I am seeing 55f on my thermometer inside the front vent. So here is my question: Why is my high side pressure so low and my low side so high? And then the 2nd part of my question; Why is it working at all if the pressures are so screwed up? This compressor only has the little air nozzles on it (see picture)and they are the same size. Take a look and see what you think? Also the high side tube sweats cold condensation and the compressor runs smooth. Thanks! http://forums.pelicanparts.com/ultimate/confused.gif

"...same size...." Both are low side pressure fittings?

aschen · 07-11-2014, 03:30 PM

are hose clamps on a high pressure line kosher?

Nick Triesch · Nick Triesch's Garage

Wow! you get 55F!! Sounds about right!

cabmandone · cabmandone's Garage

Your low side at 32 isn't bad. Your high side can't truly be 30 or you wouldn't be seeing the temperature drop you are seeing.

BTW, the low side should be sweating not the high side. The high side should be either hot or very warm to the touch.

Another thing, what is your resting gauge pressure? (A/C off) I don't know how you'd see the 16 degree temp drop without the compressor not running but it sure sounds like your compressor isn't really running and you're seeing the idle system pressure.

cabmandone · cabmandone's Garage

Quote:

Originally Posted by aschen

are hose clamps on a high pressure line kosher?

I suppose if they can hold 200 psig or better have at it but I wouldn't put them on my system.

ganun · ganun's Garage

IIRC 48 oz is for R12 , for r134 it should be less, about 35oz, again IIRC.

keithbkeller · keithbkeller's Garage

I appreciate your input on my ac system. Regarding the radiator style clamps, it was necessary for me to cut off the 45 degree metal fittings due to the need to have 90 degree turns to fit the compressor. Maybe I should add another on to each side. As far as the sweating of condensation, I am getting it as a result of the cold on the right side larger side of the compressor. (see picture). Cabmando. The larger tube on the right side is the high pressure and it is the one that is sweating cool condensation. And thanks Again for your help!

wwest · wwest's Garage

Quote:

Originally Posted by keithbkeller

I appreciate your input on my ac system. Regarding the radiator style clamps, it was necessary for me to cut off the 45 degree metal fittings due to the need to have 90 degree turns to fit the compressor. Maybe I should add another on to each side. As far as the sweating of condensation, I am getting it as a result of the cold on the right side larger side of the compressor. (see picture). Cabmando. The larger tube on the right side is the high pressure and it is the one that is sweating cool condensation. And thanks Again for your help!

Only the low side will sweat! The high side should be HOT!

According to Sanden the right side connector, nearest the fender, is the suction, low pressure side.

What you see, sweat, is the leftover refrigerant cooling capacity that supposedly a pro-cooler would use to pre-cool the liquid refrigerant prior to the reaching the TXV. Never mind that using up that leftover "cool" via the pro-cooler simply adds to the compressor workload.

What happens if you reversed the inlet/outlet port conections?

wwest · wwest's Garage

Quote:

Originally Posted by cabmando

Your low side at 32 isn't bad. Your high side can't truly be 30 or you wouldn't be seeing the temperature drop you are seeing.

BTW, the low side should be sweating not the high side. The high side should be either hot or very warm to the touch.

Another thing, what is your resting gauge pressure? (A/C off) I don't know how you'd see the 16 degree temp drop without the compressor not running but it sure sounds like your compressor isn't really running and you're seeing the idle system pressure.

The idle system pressure, "hours" after last use, should be equal on both sides and I would think in the >70 PSI range.

wwest · wwest's Garage

Sanden Selection and Conversion Guide.

Looks as if you should have purchased the newer R134a version of the SD505.

keithbkeller · keithbkeller's Garage

Hey guys, Yes in my infinite wisdom I have got the hoses going to the compressor ass backwards! I have the compressor discharging up into the rear condenser. That's why the discharge side is hot. WTF! So I wonder if I screwed up anything by running it like that? And to add to the craziness it is actually cooler inside the car!

Bob Kontak · Bob Kontak's Garage

Quote:

Originally Posted by keithbkeller

That's why the discharge side is hot. WTF! So I wonder if I screwed up anything by running it like that? And to add to the craziness it is actually cooler inside the car!

You are running it correctly. Discharge is supposed to be hot. That is why it is run into the condenser for cooling.

Discharge means discharge from the compressor. Suction means suction into the compressor from the evaporator - this is after the liquid has expanded for cooling - therefore, the inlet is cold.

The "S" or low side is cold. D or high side is hot.

Bob Kontak · Bob Kontak's Garage

Please get the hoses properly attached. In the mean time, tighten the worm gear clamp with a wrench AFTER you put a second worm gear on it. Not stupid tight, just pretty damned tight. If it were mine, I would like to see the clamp OD smaller than the hose OD.

wwest · wwest's Garage

Quote:

Originally Posted by keithbkeller

Hey guys, Yes in my infinite wisdom I have got the hoses going to the compressor ass backwards! I have the compressor discharging up into the rear condenser. That's why the discharge side is hot. WTF! So I wonder if I screwed up anything by running it like that? And to add to the craziness it is actually cooler inside the car!

Best not to bite down hard with "tongue in cheek"...

cabmandone · cabmandone's Garage

Your High side/ discharge should run to the condenser.

To the person who mentioned 70 psig, that depends on ambient and whether the system is charged properly.

wwest · wwest's Garage

Quote:

Originally Posted by cabmando

Your High side/ discharge should run to the condenser.

To the person who mentioned 70 psig, that depends on ambient and whether the system is charged properly.

The actual statement was "I would think in the >70 PSI range.."

And the statement was made in the context of someone suggesting that the OP's ~30 PSI reading might be the system idle pressure.

keithbkeller · keithbkeller's Garage

I get it now. I have it right! Well, I got confused from reading some of the other posts. All trying to be helpful. So here's the deal. I have the "D" side of the compressor going up into the rear condenser and the "S" side coming from the front of the car down the long hose. And indeed the "S" side of the compressor is cold from the refrigerant being sucked into the compressor! So now I will fit it with 2 more clamps and test it with the rear hood down!