Automotive Air Conditioning Information Forum

This is my 4th A/C job, so far. I actually kinda like it-it's been a great skill to have!

Anyway-my 1993-ish S10 standard cab pickup was pretty ratty and had the old R-4 compressor, and I was putting in remans every summer for the old boss-the company got sold and I bought the truck as I was the fleet mechanic and had all the service records already.

The 430,000 mile 2.8L V6 was pulled out and tossed, and a 3.4L version of the same engine was plucked from a 1995 Camaro and rebuilt with aluminum heads and a supercharger-I retained the camaro accessory drive, and the truck inherited the new style HD6 compressor. (and valve covers that don't leak!)

Now, the compressor is relocated down low and on the passenger side-this shortens up all the hoses, and I'll make new ones to fit. (Loosing about 2 feet of -12 hose, and 2 feet of -8 hose)

The Evaporator was replaced when I stripped and painted the truck, the accumulator/drier will be replaced, and the condenser core will be replaced. These parts were all originally designed for R12, and I can only hope the new condenser is actually a properly sized R134a unit. It's as big as the radiator already-and the S10 cab is small and newly insulated too.

Now, given that I'm loosing some system volume in hoses, upgrading to a newer style compressor, and converting to R134a, I am curious about orifice tubes and condenser core sizing-mostly the orifice tube.

Condenser core: 14 1/4" x 27 3/8", 7/8" thick. APDI/PRO 7013640
Evaporator core: Standard S-10
Accumulator: Standard S-10 (the big aluminum can type)
HD6 compressor
Camaro A/C system control-including evaporator temperature sensor and pressure sensor for the PCM (I can adjust all these parameters too)

Do I need a standard "White" orifice tube, a different color, or the "Automatic Adjusting For 105F and lower/higher climates"? The average air temp measured at radiator height off the pavement on a hot day here can get up to 120F, but generally it's around 95F. (Not the weather temp, the air temp as measured over the blacktop-It's HOT!)

How much will the 134A charge need to be adjusted considering that the internal volume of the system has changed? (different compressor, and shorter hoses)

Originally, the S10 used 40oz of R12, and 8oz of mineral oil for the compressor. The Camaro used 32oz of R134a, and 8oz of PAG150. Other than hose length and condenser core sizing, the systems are very close to the same.

I am planning to run the Camaro charge as a starting point, but I will take any advice you guys can give. I am really excited to have a chance at COLD A/C in an S10 finally-and Yes, I have fitted a heater core valve instead of running the heater core all the time!

Run what ever O/T the S10 evaporator is supposed to have.

So called "automatic" orifice tubes are a waste of time.

That's good info-I have heard to use a "blue" tube or the automatic tube instead of the factory white tube.

I did not know if the orifice tube was sized based on working gas, coolant load, or evaporator size-so in this case the S10 should be fine with the OE tube.

So this is working now-Charged today.

Having some issues with it though, namely that it only works at idle. That's a program issue with the computer, I'll sort that.

But, watching the gauges and measuring vent temperatures...

I charged with 8oz PAG universal oil, and 1.8 lbs R134A-because I just could not get it to take that last 0.2lbs of gas. (both the S10 and Camaro systems specify 8oz oil and 2lbs refrigerant for R134A) My system has much shorter hoses and hardlines-but that shouldn't matter too much, right?

With the compressor not engaged, at 90F ambient temp and stationary the system pressure floats around 68-70PSI.

With the compressor engaged, at 90F ambient temp and stationary, the high side peaks about 275PSI, and the low side sits around 45psi. The compressor does not cycle, and the evaporator inlet (right after the orifice tube) gets nice and frosty, but the evaporator exit is only moderately cool. The accumulator does not get all sweaty like it should, and only gets a little cool. (compared to the 150F air coming out of the fan shroud, anyway...)

Driving around, the engine computer logs high-side pressures so I can watch the high side pressure while I drive-it peaks out at 140psi. This is with 20-40mph airflow plus the engine driven viscous clutch fan running, so the condenser should have adequate airflow.

Vent temperatures are slightly disappointing at 48F, but given the pressures seem a little off I am not surprised. Also, the S10 has the heater core running constantly as per factory design, so first thing on my list is to check the blend door and make sure it's closing all the way in A/C mode.

Do these numbers sound correct, or have I got a problem going on that can be solved to improve the A/C performance? I am told to shoot for 40F vent temperatures, and that's what I have achieved on the other A/C systems I've worked with.

You have two problems.

1) Condenser airflow at idle.

2) Undercharged.

At idle you have high pressures. Typically a sign of poor condenser airflow. Weak fan / No shroud / Air bypassing condenser.

At cruise you have low pressure, and poor cooling. Typical for an undercharged system that can't flood the evaporator.

You need to fix the airflow issue first, because a proper charge will make the idle pressure worse.

Can you post a pic of the condenser install?

It's a factory style condenser in the factory location. It's the same tube-and-fin as the original condenser, but I will do the hose test on it today to verify low heat rejection on the condenser.

Brand new fan clutch, fan shroud, and condenser. The only thing in front of the condenser is an oil cooler that is 8"x5", and the condenser is 14"x27" of actual finned area. I'll get pictures today.

The undercharge-what can I do to get the charge into the system? I can let it sit and sit and sit with the bottle open and the gauge set open and the low side pressure doesn't seem to go down any further-I am absolutely sure I only have 8oz oil in the system, too.

Photos coming soon.

What diameter fan are you running?

You can usually charge the last bit easier at 1800 RPM - the low side should drop. With a low side below 50 psi, at 90f ambient the refrigerant should be at a higher pressure & flow just fine.

Record your stable 1800 rpm pressures & post them here.

So, I took another afternoon to work on this yesterday. No improvement...

At idle, after recovering the system, flushing the oil out, and replacing the accumulator, I made sure the compressor had 4oz of oil in it, and charged the system with 4oz oil. Then I filled with 2.0lbs of R134A, exactly the required amount.

I had to bump the idle up to 1600RPM to get the last of the 2.0lbs in there. But it went in, and the acuumulator built up a very good sweat-and the air out of the vents was ice cold. Low side pressure was 36psi, high side pressure was 200psi. High side fluctuated a LOT at idle, but got steadier as the idle speed got up. Low side pressure came up to 40ish PSI at idle, but as soon as the throttle was cracked pulled down to 36psi, and the high side pressure started climbing to between 200 and 240PSI.

So, I thought I've done this now, it'll be great! Took a break, put the tools away, watched the eclipse, and then hopped in the truck to go grab some lunch...and mediocre air conditioning at best. The longer I sit at idle, the colder the vent temp. If I'm cruising around, I get zero cooling if I am on throttle, and recover cooling slowly as long as I am coasting or decelerating. Any kind of accelleration kills the vent temperatures.

Bad compressor?

PCM disabling the compressor above 30% throttle?

Full load test
With the doors open, and the cabin fan on highest speed, run the engine at 1800+ rpm for one minute. Record the pressures while the engine rpm is above 1800.

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I love my Ranger. Its an 03 so you probably wont find one for 3-4k, but its an awesome truck. I also had a 92 Ford F-series and I liked it. I think Ford just makes good solid trucks.