A/C ports location.

[Derekw66]

Does anyone know which port is the high and low?  There is no labeling and the hoses are about the same size.  I’m in the process of converting the system to 134 but can’t tell which is which.  The shop manual doesn’t specify either. To be clear, it’s a 91 Chrysler TC Maserati with the v6. Thanks in advance.   

[Hemi Dude]

If you have the 2 adapter ports needed to attach to the high and low pressure ports on the R12 system, YOU will notice when you remove the plastic caps on the A/C lines, that one port is smaller, that is the high pressure port.

The other, larger is then the low pressure port.

Your adaptors will only screw on to the correct ports.

 

I hope this helps.

[Jim Bird]

I need to convert the AC on my 1990 16 valve from R12 to 134a. Very interested in what components you are replacing and in others experience in doing this.

[Hemi Dude]

30 minutes ago, Jim Bird said:

I need to convert the AC on my 1990 16 valve from R12 to 134a. Very interested in what components you are replacing and in others experience in doing this.

Just so you are aware, I have never done a conversion, always had a friend who only did AC repair take care of that since I was in CA and you had to have separate equipment for each system for evacuation, etc.

Jim, I would recommend taking your TC to an AC shop for an estimate.

That way you will get the best idea of cost and parts, especially since you have the GM compressor and you may even need major components replaced in order to have a dependable system.

[Derekw66]

Pretty straightforward actually, I replaced the dryer, expansion valve and compressor, including replacing all o-rings.  Flushed the evaporator, hoses and condenser. Put it under vacuum overnight and added 34-36oz of refrigerant.  Got it blowing 38-39 degrees tonight.  Also, fyi, the lower fitting closest to the compressor is the low side.  Both ac valves on my v6 were the same size and neither one was marked.  My biggest headache was the different 134 bottles, some are the puncture style, some are self sealing, some have their own nozzles.   

[Moparite]

Did you put in pag oil? The oil that was used in the R12 systems should be removed as it deteriorates the performance of the R134.

[Derekw66]

I did a complete flush of all appropriate components and added a few oz of pag due to the compressor already having the correct amount for it, in it. 

[shelbyone]

On 10/19/2019 at 11:55 AM, Derekw66 said:

I did a complete flush of all appropriate components and added a few oz of pag due to the compressor already having the correct amount for it, in it. 

Hey Derek! can you tell me how much PAG you had to use?

[2Shelbys]

I’m going the other way with my TC. Away from R134 and back to R12. Colder and less likely to leak. Also not flammable but I’m not planning on having any fires anyway. 

[RobertLDuncan]

To be clear, if an R12 system has a catastrophic release of gas it will be an atomized cloud of mineral oil, which would be very flammable. 

[Hemi Dude]

4 hours ago, RobertLDuncan said:

To be clear, if an R12 system has a catastrophic release of gas it will be an atomized cloud of mineral oil, which would be very flammable. 

In the 24 years I spent as a dealer mechanic and then another 24 in my own shop, I have never seen an engine fire as a result of a rapid, catastrophic, refrigerant discharge. 
On our turbo TCs, a fuel fire from old cracked fuel hoses and incorrect clamps is much more likely.

[RobertLDuncan]

What I was pointing out is you don't pick a refergrant based on flammability.

 

Even R290 (propane) isn't really any more dangerous than R12 or R134a when the oil mist is present in a large leak.