AC Help

[RangerJoe]

I recenlty replaced my condensor and recharged my already converted R134 system...everything went well.

Yesterday I helped a buddy of mine with his system on a 91 gt. He bought the car about 4 years ago with a non functioning R12 system. Slowly over the past several years he has been replacing parts. He has replaced the evaporator, the dryer and the compressor. He did not replace the oriface tube or condensor.

We pulled the vacuum and charged the system....no leaks. The problem is that the air out of the vents gets no colder than 60 degrees. He talked to a mechanic friend of his who told him the R134 needs a specific oriface tube and that the R12 one is not in spec and is most likely the cause of the poor cooling.

I have looked at all my favorite mustang suppliers and cannot find one that says it is for a specific system. The ones on the Autozone website say they are compatable with both style refridgerants, which would mean that the mechanic friend is wrong???

Does anyone know if the oriface valve is specific to R134? If not, what would your guess be as to the source of the poor cooling?

Just a note: We checked the blender door and it appears that it is fully shutting.

Thanks for any help!

 

[oldfox]

When I did my V-8 conversion on my Fox I replaced the orifice tube and it was built in the line. I checked everywhere and no one had one for pacifically
134e The only part I found that was for 134a and avable for my 91 Fox was the low side pressure switch. Only thing is to get it to blow really cold I had to undercharge it Correct amount of oil and only 28oz R-12
I know that sounds silly but it worked

 

[Mustang5L5]

There is only one orifice tube. It will work with both, but be more efficient with r-12

The accumulator should have also be changed...especially if it's been an open system (ie leaks) for some time. There is a way to "recharge" the accumulator but it involved pulling a high vacuum on the system for 24 hours or more to "boil" out any moisture.

The system is not as efficient with 134a as it is with r12, but you should be seeing temps better than 60 degrees. How much r-134a did you charge with? You need to us LESS r-134a than r-12. If ypu overcharge, or undercharge, it could have an effect.

 

[jrichker]

The correct R134 refrigerant charge is 26-28 Oz plus 6-8 Oz of PAG 100 oil.

See 1994 condenser in a 1987 - 1993 stang? - Ford Mustang Forums : Corral.net Mustang Forum for a very interesting discussion on boosting idle speed cooling power in R134 conversions for Fox body Mustangs.

 

[RangerJoe]

I may be referring to some of the items by the wrong name...We did replace the accumulator (dryer as I called it). We used 8 oz of the PAG oil for R134 systems.

I forgot to mention that the pressures were all on the high side of their limits. The low side was somewhere around 60 and the high side around 370ish. This was inside a 100 degree garage (per thermometer on wall), about 94 outside, but running car made it much hotter. At the time I thought the presssures were high because of the excessive heat. The high temps made the car run a little warm in the garage, but all temps taken from the ac vents were done on the highway at highway speeds with car running at operating temps.

By the way, we used almost three 12oz cans...hard to tell how much was left in the last can. I would guess less than half. So we are probably somewhere about 30oz or so in the system.

How can we go about lowering the pressures? Does anyone think this is the culprit?

Thanks for all replies!

 

[jrichker]

You must have missed my previous post. You have overcharged the system. Proper charge is 26-28 Oz of R134 - that's 2 each 12 Oz cans .

Drain some refrigerant out until the low side pressure runs about 24-30 PSI while the engine is runing 1200-1500 RPM. Put a fan in front of the car to blow cold air on the radiator while checking & charging the system. Turn the A/C blower on high and roll up all the windows to do any testing or charging.