A/C overheats engine?

[reno]

How much R-134a is normally needed to fill a system in a 93 Ranger that once was R-12? 2 12oz cans?

 

[MAKG]

The rule of thumb is 80% of R-12 capacity. The R-12 capacity is on the blower housing label. It's usually close to 2 cans.

 

[reno]

Soooo, if the R-12 system takes 2 cans which is 2 12oz cans which = 24 oz or 1.5 lbs, then R-134a would be about 1.5 cans or ~19oz?

 

[MAKG]

Don't guess at capacity. You'll make a POS.

READ your label. Fill it to 80% capacity with R-134a (after cleanup, repair, etc.).

 

[DesertStorm]

Don't guess at capacity. You'll make a POS.

READ your label. Fill it to 80% capacity with R-134a (after cleanup, repair, etc.).

Yes 80% capacity is correct. But you do not have to get the scales and slide rulers out. Charge as liquid only and slowly fill it up. Watch the suction pressure. At around 32-35# it will stop pulling down and shutting off on the LPS. Charge it a little more. 38-42# depending on temp/load. Put a temp. probe in the vent. Charge only on MAX AC with fan on high. temp out of vents will get to around 40-44 deg. F. Bring rpms up to about 2000-2500 pressures will drop back down to the lower 30's. Should be really close.

 

[Bob Ayers]

Yes 80% capacity is correct. But you do not have to get the scales and slide rulers out. Charge as liquid only and slowly fill it up. Watch the suction pressure. At around 32-35# it will stop pulling down and shutting off on the LPS. Charge it a little more. 38-42# depending on temp/load. Put a temp. probe in the vent. Charge only on MAX AC with fan on high. temp out of vents will get to around 40-44 deg. F. Bring rpms up to about 2000-2500 pressures will drop back down to the lower 30's. Should be really close.

Be very careful liquid charging that you don't slug the compressor.

 

[reno]

Well now see, that is what I did. I drained the A/C down to where the clutch would cut in and out rapidly. Then I hooked up my can of R-134a and began filling. Low side was around 18 - 20psi. Filled till low side had a reading of around 32psi. I checked my temp in cab, in center vent, a/c on max, fan on high, it read 78F. Brought rpm's up to 1000 then 1500, no change in temp. It was about 94F outside, I was in the shade, about 90F. Low side dropped to about 28psi. So I started filling again, till gauge showed 32psi, temp dropped to 62F, brought rpm's up to 1500, temp went to 60F. When I went back out to the gauges and revved the engine (do not know what RPM) high side would keep increasing, and let off throttle, would come back down quickly. Clutch never cut out though.
What is the best way to know if it is overfilled, or what to look for next? I am about ready to completely drain, replace that orfice, pump,then refill, but really do not want to do this if not necessary.

 

[DesertStorm]

Well now see, that is what I did. I drained the A/C down to where the clutch would cut in and out rapidly. Then I hooked up my can of R-134a and began filling. Low side was around 18 - 20psi. Filled till low side had a reading of around 32psi. I checked my temp in cab, in center vent, a/c on max, fan on high, it read 78F. Brought rpm's up to 1000 then 1500, no change in temp. It was about 94F outside, I was in the shade, about 90F. Low side dropped to about 28psi. So I started filling again, till gauge showed 32psi, temp dropped to 62F, brought rpm's up to 1500, temp went to 60F. When I went back out to the gauges and revved the engine (do not know what RPM) high side would keep increasing, and let off throttle, would come back down quickly. Clutch never cut out though.
What is the best way to know if it is overfilled, or what to look for next? I am about ready to completely drain, replace that orfice, pump,then refill, but really do not want to do this if not necessary.

Still sounds like you have non condensables in your system. ie air,moisture. Pull a 30 min vacuum on the system and check for leaks. make sure your gauge stays pegged at 30" of HG. If it holds your good. Then charge. If you start from square 1 usually all problems and mis diagnosis will be eliminated.

 

[DesertStorm]

Be very careful liquid charging that you don't slug the compressor.[/QUOTE

You are correct. It has to be slowly metered in. Not full blast but, 134A is a blend. It HAS to be charged as a liquid or some of the refrigerants will seperate and not be fully mixed in the system. Can cause some strange behavior. Only azeotropic HFC/CFCs can be charged as a vapor. R22/R12/R502/R500 etc etc. Old refrigerants.

 

[reno]

now to charge as a liquid is to hold can upside down and vice versa for vapor, correct? Because every so often I "shake" (twist, whichever way you want to look at it) back and forth from 12 o'clock to 6 o'clock. Instructions on the can says to do this.

I was also wondering if my evap was dirty with dust\dirt, or who knows, maybe even mud from the P.O., would that not cause these symptoms as well? If so, what is the easiest way to get to it?

 

[AllanD]

I'll add that if your engine is overheating you likely have an issue with a coolant radiator that atleast partially plugged OR you have a lazy thermostat.

My AC is working perfectly and even standing still in 95degree ambient temps the engine temp guage approaches, but never actually gets to the halfway mark

Typically the label on a '94 Ranger/Explorer evaporator housing
specifies 1.5lbs of R-134a

that is EXACTLY two 12oz cans of referigerant.

The typical Ranger/Explorer system is specified for 1.75lbs of R12.

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[reno]

I ask again, to liquid charge, is this to hold the can upside down? And to do this, the best method would be how? short bursts, semi short bursts (i.e. short burst=10-20 sec, stop for 10sec then repeat\ and semi burst=20-30sec stop for 10sec then repeat).

 

[AllanD]

When I am starting with an evacuated system

I add a 12oz can by holding it upside down and letting it all go in one shot.

the second can tends to go a bit slower, but you can still feel the
can "go light" as the compressor stops cycling.

Why use small cans? because you know how much is in them, I never really trusted the load cell in the recycling machine.

and besides that machine won't give up the referigerant when the level drops below a certain point, so you'll tell it to charge 1.5lb and it'll stop at 1.1 at which point you'll need to GUESS how much of a 12oz can is 0.4lbs

the ranger system holds 24oz or R134a so when the second can is empty
you are done.

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