My 88 ranger had a/c at one time but the previous owner ripped everything out but evaporator.

I replaced every single component including:
Remanufactured Compressor (Fs-6 ready-aire)
evaporator
condenser
all refrigerant lines
reciever/drier
orifice tube
all new green orings lubed with blue nylog
new low pressure cut off switch

Okay, so heres what happened. as you just read i put in a complete new a/c system. the orifice tube i used was a variable orifice/smart VOV.

I vacuumed for 1 hour and verified it held 30 inches overnight. I added 8oz of Ester oil to the compressor and drier before buttoning it up.

when i went to charge it, i know the variable orifice can be a little screwy with charging by weight(still had r134 cylinder on scale anyway), and i heard its better to watch vent temps also whilst charging. i had a digital thermometer in there.

with vehicle at about 900rpm i started charging. when there was about 1 lb 5 ounces or r134a (r-12 oem specs are 2lb 2oz) the vent temps werent getting any colder at about 43 degrees. at this point the low side was about 40 and high was like 230. as soon as i raised the rpm over 1000 the low side went way down and high went well over 250. when it hit about 280-300 something was causing the compressor to be hard to turn(almost seize up and the clutch would screetch like crazy). so i recovered some of it down to about 1 lb or less and the low is at about 15 psi and high is 250-260. at this point at idle vent temps were 60, and at 2000rpm with fan on condenser they were 54.

i thought there was a problem with the variable orifice so i recovered everything and put in a new ford red fixed orifice. basically the same issue, maybe a hair better. i got about 1 lb of refrigerant in and at 2000 rpm the high side is pushing 250 with the low at 10-15 (had to adjust screw in cut off switch to get it to run that low). this is where im at now.


i cant figure out what could be faulty. i know it should have at least the 1 lb 5oz because the air is ice cold at that that charge but anything over idle and the high pressures climb all the way 300+ psi till the compressor starts to lock up. the only way to prevent the pressure on the high side from going through the roof is to only charge it about 15-16oz of r134a. and still the low is like 10-15 psi so that charge cant be right at all. what is going on here! is the remanufactured compressor bad?

any help is GREATLY appreciated.

 

If the compressor can make 300+ psi, there's nothing wrong with it.

It sounds like you have a condenser airflow issue, likely a bad fan clutch.
Raise the idle and mist water over the condenser from your garden hose. If the High Side pressure plummets, it's an airflow problem. Since everything else is new, replace the fan clutch. It's 23 years old and outlived it's life span.

Also, if there were any air dams or seals between the grille, radiator and condenser, they need to be properly installed. This is very important on converted systems. You need all of the airflow over the condenser that you can possibly get.

 

I put a shop fan over the condenser, and tried the garden hose. It didnt really change much at all. Maybe dropped 2 or 3 psi. The fan clutch also seems to be normal.

Could the cheap aftermarket condenser be the problem? A faulty internal restriction?

Thanks

 

Maybe. I've seen debris in new condensers. I usually flush them before installation for that reason, just to be sure.
Feel the surface of the condenser. Cold spots would indicate a restriction.

Are you sure the orifice tube is in the right way? The short end goes in the evaporator tube first.
Some Fords of that era had the orifice as part of the liquid line. Adding one to the evaporator inlet would cause problems. Maybe you have 2? Look for a crimp in the steel line near one end.

 

I will check it for cold spots. I am convinced it has to be something with the condenser
The condenser is not the tube-and-fin design it is the other kind. I think parralell flow?
I ordered a used oem one off ebay to try but all the oem ones are tube and fin. Which is better?

but the orifice crimp is on the evaporator inlet. The big white screen is facing the condenser and the small end is facing evaporator. The only thing that was still in the vehicle when i got it was the evaporator and it still had the orifice in it. I replaced the evaporator anyway and put the new orifice in the same way the original was from the factory.

Am i on to something with the poor condenser design?

 

There are Serpentine (single tube back and forth, 50-60s type), Tube and fin 9multi pass, 70s-90s design) and Parallel flow (mid 90s and up). Yours is probably Tube and fin.
I doubt the condenser design is the problem but it could be defective somehow. You might want to have the refrigerant recovered and check the orifice tube for debris from the condenser. It could be something dumb like a piece of a packing peanut.

It sure sounds like you did everything right in the beginning. This really smells like an airflow issue, though. .

 

The condenser is not a tube and fin. I double checked and it is definately parallel flow. Idk why bc the factory was tube and fin. I would definately agree with the airflow but with a good fan on it and some cold hose water doesnt change a thing.

The used condenser i ordered is tube and fin and is oem. It seems all the cheapo aftermarket ones are paralell flow. And the name brand are tube and fin. I really hope the swap works.

When i changed the orifice tube becuase i thought it was faulty, there was no pieces or anything in the screen. Just oil that was a hair bit dirty.

I just dont get it. It doesnt make sense. It should be working fine. The only thing that makes me disagree with the airflow issue is that the hose water did nothing and the high powered shop fan did nothing to the pressure.

Thanks again for your help

 

Do you have a way to measure the temperature of the lines at the condenser? If so, you should get about 25 degrees temperature drop across the condenser.

Where is the High Side service fitting located on the vehicle. I seem to remember it being in the compressor discharge line.

I can guarantee the condenser is not parallel flow. There are only a very few types of direct fit PF condensers available for R12 systems. I've only seen them for some Mustangs and Corvettes.
I wrote my description wrong. Tube and fin is a lot like the coil on an old refrigerator, one tube back and forth. Serpentine looks a bit like a radiator. Sorry.
I used to have a really good illustration of the different types and their flow.but can't find the darn thing.

 

I have a dvom with a temp probe. Will that work? If i just stick it right to the line?

It must be the serpentine then. I just know its definately not tube and fin. I have one on my 1991 f250 and it looks just like the used oem one i ordered. The one on there now has no "u" tubes on the sides.

The service port is on the discharge line about 2 inches before it goes into the condenser.

 

Yeah that should work. Can you feel a big difference in the condenser lined with the AC running? A large difference could indicate a restriction.
I wish there was a way to check the pressure on the outlet side of the cond.

 

a big difference where at? between the inlet and outlet? or do you mean at any point along the discharge line?

 

Big difference between the condenser inlet and outlet.

The whole High side should be "hot. After the orifice tube and back to the compressor should be "cold".
If you encounter "colder" on the high side, that usually means a restriction.

 

Since you do not have matched components, ie, evap, condensor, compressor etc, you are going to have to waiver from factory charge amount, likely orifice size etc.

The pressures above 900 rpm are counter to what should happen in a properly designed system. As high side pressure goes up, low side pressure should also go up in a system with orifice tube. Conversely, as high side pressure goes down, low side should go down. You have the opposite happening.

I would start by doing something to at least get the high and low side pressures following each other. When you increase the rpm, the compressor is pumping more, or at least trying to. Since your low side is going down and high side going up, the first thing I would try is an orifice tube with a larger orifice to allow more refrigerant into the low side. My theory is that the compressor is pulling the low side down too far because the orifice, or some other restriction, is not allowing enough refrigerant to flow back to the compressor. When this happens, the low side vapor has a higher superheat which will cause the discharge gas to be hotter and therefore higher pressure.

Find a 134a pressure/temperature chart onlline, you are going to need it and also learn to calculate superheat on the low side and subcooling on the high side.
superheat = low side pressure converted to temperature compared to the low side line temperature measured with your digital probe. When measuring the temperture, put a piece of black rubber pipe insulation or a dry rag over/around the area of the pipe such that the end of the temp probe is covered by the insulation or rag. If insulation, just poke the probe through it and be sure to go all the way thru to the pipe. This is the only accurate way to measure line temp because you have to eliminate the effect of the surrounding air temp.

Here is a chart online for 134a:
Pressure - Temperature Chart for HFC-134a

Superheat example:
low side pressure of 40psi = saturation temp of 45(rounded off). Now, measure the line temp and I'm guessin' it will be above 45. Line temp minus saturation temp from chart = superheat. Note: measure the superheat on the line between the evap and the accumulator, this will give you the superheat across the evaporator.

Tell us what the superheat is at 900 rpm. I'm betting it is high, meaning 20+ degrees.

Next I would put in a larger orifice tube and the same amount of charge and measure superheat again at the same rpm. IF the superheat went down, to around 10-15 degrees, you should probably see a change in that the high side is not going so high.

You should also use your temp probe and measure the low and high side pipes and check for an extreme difference. Example, temperature at the outlet of the evaporator headed to the accumulator, compared to temp between accumulator and compressor. Any temp difference greater then 2 degrees is unacceptable and indicates a restriction.

I kind of doubt you can force enough air thru the condensor with the shop fan to make much of a difference. Replace the fan clutch to make sure it kicks into high when the air warms up due to the condensor warming up. Don't play down the air flow requirement across the condensor. Make sure all shrouding is in place to get max air flow across the condensor.

Measure temp difference between high side coming out of condensor to high side pipe before the orifice to check for extreme change which would indicate a restriction.

Subcooling: Condensor condenses the freon to a liquid by removing heat.
High side pressure converted to saturation temp using the chart minus the high side line temp coming out of the condensor equals subcooling. The high side line temperature should be lower then the saturation temp of the high side. If it is not, there is not enough charge in the system or the airflow across the condensor is too low. No subcooling means there is no liquid freon at the orifice and you need liquid there.

Enough said for now. Try a larger orifice and drench the condensor with cool water to try and make a change. Measure line temps to determine any pressure drops in the lines.

 

Wow thanks for the info. So what color orfice should i try? I am using a red ford one now. Is blue a bigger size?

I just ordered a 2350 cfm 16 inch fan to put on the condenser.

I wish i hadnt left this at the shop over the weekend as i am not able to go mess with it till this week.

So what should i try first?

I have a oem used condenser coming, and a 2400cfm fan.

I think i should check for restrictions and cold spots first, and add the fan to the system as-is before changing condensers or orifice size.

What do you think?

 

According to this web site:
Orifice Tube Color Chart

blue is the largest.

You are using red which is only one size under. Give the blue a shot and see what happens.

By the way, you said when you pumped down the system, it held 30" vacuum overnight. Was this with the vacuum pump off and the valves on the gauge set closed?

Don't forget to get the superheat and subcooling readings and check for temp diffs on the low and high side pipes.

Later