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A college kid and his Chevrolet C10

m_misztal on Fri July 12, 2013 5:21 PM User is offline

Year: 1986
Make: Chevrolet
Model: C10
Engine Size: 305
Refrigerant Type: r-134a
Ambient Temp: not very
Pressure Low: unknown
Pressure High: unknown
Country of Origin: United States


This message is brought to you from the hot and steamy temperatures of College Station, Texas, home of the Texas Aggies.

I have an old school chevrolet c10 truck that has been giving me troubles since i converted over to the r-134a system. I originally had the r12 system with no problems whatsoever until one day the compressor gave out. After a few awful months without a/c I finally managed to save up enough money in order to convert over to the r-134a. I did my research and had the following items replaced: compressor, accumulator/dryer, rubber hose assembly, and orifice tube. Well this work was done about a year ago now and the a/c has never really worked as well as I would have liked. I decided that cleaning my condenser may help me head in the right direction. I cleaned the condenser grill with a brush and sprayed it with coil cleaning foam. This helped me very little.

I can see the fan clutch spinning and the water pump which is powering the radiator fan is also doing its job. Don't get me wrong the a/c does work to some degree but i'm about at my wit's end with this dilemma. I've been told that the condenser has to be replaced and i've also been told not to touch it. My other suspicion is that the proper amounts of oil and freeon were not added into my new a/c system.

I live in Texas and the heat outside last night without the heat index with humidity was 107. If there was any way i could get even a shred of information I would greatly appreciate it. I work full time and go to school full time, so i'm willing to put the money into fixing this correctly so that I may finally wash my hands of this awful situation.

A hot and sweaty Texas Aggie c/o 2014


m_misztal on Fri July 12, 2013 8:10 PM User is offline


fix_it on Fri July 12, 2013 9:37 PM User is offline

Here I go again... I just typed this, but the computer deleted it. Oh well.....

Hi. I have a 1985 Suburban that I converted to R134a. It will blow 35 to 40 degree air on high fan. I think I can help you get yours to cool also. I will share what I did to mine. It took about 5 years of working on it, doing one thing and then another, but I think I have it figured out.

1. Make sure you have the proper amount and type of oil in the system. The only way to do this is to flush the system, then add back the correct amount of oil. Too much oil causes poor cooling. The desiccant in the accumulator holds oil and can't really be drained, so you will need to replace the accumulator.

2. Get a new severe duty fan clutch. They wear out slowly. After about 5 years, they are pretty well worn. Even if the engine doesn't run warm, poor AC performance is the first sign of a worn fan clutch.

3. Replace the old condenser with a parallel flow (best) or 6mm type. The parallel flow is likely to be a universal type, as I haven't seen one specifically for these trucks. This means it will have to have custom jumper hoses made to connect it to the factory lines. The 6mm type is readily available. The aftermarket replacement condenser for this truck is now a 6mm condenser. These can be found at the site sponsor ACKITS.COM. The old condenser is just not up to the task with R134a.

4. Seal the fan shroud to the radiator, and the radiator to the condenser. Make sure all the air has to flow through the condenser.

5. Install an auxiliary electric fan. Wire it through a relay to run when the compressor does. This will make a huge difference at idle and slow speeds when the radiator fan is turning more slowly.

6. Use a Ford blue orifice tube. It will fit the GM evaporator just fine and has a slightly smaller orifice. It seems to work better in GM conversions than the stock white one.

7. Install a vacuum operated heater shutoff valve. The GM cars of this vintage had them, but the trucks did not. They needed them. Get one for a 1988 Caprice. It goes in the 5/8 heater hose from the intake manifold. The vacuum line will tee into the recirculate door actuator behind the passenger side kick panel. Now, when you turn the lever to MAX AC, the heater water will be shut off. This prevents the heater from reheating the air. It made a 5 degree difference when I installed mine.

8. Pull a good vacuum. Charge with R134a until the outlet of the evaporator is within a couple of degrees being as cold as the inlet. Then add a couple more ounces. This extra will be stored in the accumulator and will ensure an adequate supply of refrigerant to the evaporator at all times.

9. Adjust the cycling switch on the accumulator. After the system is charged, unplug the blower fan and watch the low pressure gauge to see where it cuts off at. Unplug the switch and look between the two blades. There is a screw. Adjust this screw to lower the cutout pressure to around 20 to 25 psi. You want it as low as possible without freezing up. You have to adjust this because R134a needs a lower pressure that R12 to have the same temperature.

Do all this and it should freeze you out.

iceman2555 on Fri July 12, 2013 9:43 PM User is offlineView users profile

From the posted information, it appears that the system is not charged properly. The vehicle produces cooling…just not to expectations. This would eliminate the need for a new compressor…unless there is another issue with the unit…noise etc. The compressor DOES NOT COOL THE SYSTEM. It is strange why this is the part that gets blamed for not cooling issues.
Since most retro’s were undercharged as a guide and the amount of refrigerant charge was often determined by an attempt to achieve a perceived operational pressure, it would appear that the installer did not service the system correctly. Many attempt to charge to what would be believed to be an acceptable pressure for r12. Keep in mind that 134a operates at a much higher pressure than 12 and will often produce high side pressures that would at face value appear to be ‘out of spec’.
There is a simple test that you should be able to accomplish and does not require expensive tools. Place the vehicle is high heat load….MAX AIR…..HIGH BLOWER….BOTH DOORS OPEN….ENGINE AT IDLE. Engage the compressor and allow the system to operate for app 5-7 minutes. Determine the evaporator inlet (cool side of the orifice’ and the outlet (prior to the accumulator inlet). Simply touch the lines with your fingers….not an exact measurement…but should be a guide.
The temps should be the same or very close to the same. If the outlet is warmer than the inlet…the system is undercharged and should be serviced. Not simply adding refrigerant….have the system serviced by a tech with a recovery machine or a charge machine that will allow for proper recharge. Use a guide of 90% or the OE charge of r12.
Discover if the installer did indeed flush and remove all residual mineral lubricants. This should be done to allow for the correct amount of lubricant in the system. Excessive lubricant may effect system performance also. But first the proper charge rate needs to be determined.
Good luck.

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

94RX-7 on Fri July 12, 2013 10:10 PM User is offline

Originally posted by: fix_it

3. Replace the old condenser with a parallel flow (best) or 6mm type. The parallel flow is likely to be a universal type, as I haven't seen one specifically for these trucks. This means it will have to have custom jumper hoses made to connect it to the factory lines. The 6mm type is readily available. The aftermarket replacement condenser for this truck is now a 6mm condenser.

It actually appears that ACDelco now makes a parallel flow unit for this truck P/N 15-6960

fix_it on Fri July 12, 2013 11:25 PM User is offline

I don't think anyone said to replace the compressor. I said that a better condenser was needed. This is purely from my experience with this same system. If all the things I suggested are done, it will cool great. The factory condenser on these was been too inefficient on the several systems I have worked on.

The way I read the original post, this is a new retrofit and has never worked right. It has not been said what the exact procedures were when the retrofit was done. The original poster suspects too much oil. All this leads me to suspect that the conversion fitting were added, along with some amount of new oil and then recharged. The original compressor failed, but we aren't told if the system was flushed. There was probably some amount of old oil and maybe debris left in the condenser and evaporator. Everything else was replaced, though.

If we had some pressure readings and vent temps, that would be helpful. However, based on what I have seen with these, I would start by flushing, installing a blue orifice, a new accumulator, and a new 6mm condenser. Recharge till the evaporator in/out are the same temp and readjust the cycle switch. Then see what happens.

m_misztal on Sat July 13, 2013 12:56 PM User is offline

For everyone who replied within the last day I cannot express my gratitude enough. I'm on a pretty set budget of 200 bucks at the most as of right now so I'm trying to get the most bang for my buck. The system was flushed or at least I was told that. I'm going to one of the most reputable shops in my town to hopefully have this fiasco under wraps. I have all the conversion fittings and everything installed so I believe I'll just start with a parallel flow condenser. My only problem now is that I have Monday and Tuesday off and I need to track down this part at a local auto parts store in order to have it in hand before I drop my truck off to have it worked on.

fix_it on Sat July 13, 2013 1:06 PM User is offline

Since you need the condenser in a hurry, you may not find that Delco PF unit. You should be able to find the 6mm condenser in stock at a local parts store. I got mine from Autozone about two years ago. Since you need it Monday, that may be your only option. Otherwise the PF condenser is more efficient. However the 6mm cools my Suburban, so it should be good for a pickup.

While they have it apart, make sure it has a Ford blue orifice tube. They are listed for 199? Taurus, among other Ford products. It will help. Should only be a couple of dollars.

See how that works, and if it gets warm at idle, you need an electric fan.

m_misztal on Mon July 22, 2013 6:53 PM User is offline

Thanks for all of the replies from everyone. I was able to figure out that the system was improperly charged. I flushed out the system and had a legitimate shop add the correct amount of freeon and oil to the system. On top of replacing the compressor again because it was under warranty I'm very pleased with the results. I'll be installing the heater shut off valve within the next few days and hopefully I'll get some even better cooling coming out of the vents. I recorded it coming out of the vents at 40 degrees. I didnt replace the condenser, I didnt seal the condenser to the radiator, and I didnt get an auxillary fan, but i will say that I'm happy with my results so far. The blue ford orifice tube seemed to give me a fighting edge.

Thank you to everyone who helped a college kid on a budget solve an issue that had been bothering them for almost two years.

fix_it on Tue July 23, 2013 10:08 PM User is offline

Glad to hear you got it fixed. 40 degrees is quite good. The heater cutoff valve will make it a couple of degrees cooler. That really makes a difference on those very hot days.

iceman2555 on Wed July 24, 2013 11:00 AM User is offlineView users profile

Great to hear of a successful repair. Glad the system is functioning to your satisfaction. Key to any successful AC repair...know it is properly charged. This is the most important part of any repair or system performance diagnostic procedure.

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

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