66 Monaco Wagon Preservation

An update on my A/C situation - I took the car to another shop I have used, they are more of a custom / hotrod shop not afraid of older cars. There was still a lot of head shaking but they are willing to give it a try - at my expense of course. Like others they recommend at minimum flushing, replacing charge ports, expansion valve and filter dryer, oil replacement and R134a charge. I am inclined to take a gamble with them with an understanding that the checkbook is not totally open.

Another thought popped into my head, I have been offered a source of fairly reasonable priced R12. Would it make any sense to go back in that direction and if I did are R12 compatible parts like a filter drier even available?
 
An update on my A/C situation - I took the car to another shop I have used, they are more of a custom / hotrod shop not afraid of older cars. There was still a lot of head shaking but they are willing to give it a try - at my expense of course. Like others they recommend at minimum flushing, replacing charge ports, expansion valve and filter dryer, oil replacement and R134a charge. I am inclined to take a gamble with them with an understanding that the checkbook is not totally open.

Another thought popped into my head, I have been offered a source of fairly reasonable priced R12. Would it make any sense to go back in that direction and if I did are R12 compatible parts like a filter drier even available?

I think that a return to using R12 is not a good idea since as far as you know the conversion to run R134A has already been done. Yes, all the correct parts to make the return to running R12 are available, but... my vote is to try what the second shop is suggesting. Ports, flush, exp valve and new dryer and oil. I still advocate a dye charge at the same time to look for leaks.
 
Something to keep in mind: When converting to R-134, you are supposed to remove the EPR valve in the back of the compressor, and install a temp switch on the evaporator core to cycle the compressor on and off when needed. Chances are that the EPR valve is shot anyway. I bought three NOS EPR valves a few years back, and none of them worked. The temp switch is cheap, but getting the probe into the evaporator on a '65-'68 will be a challenge. Being in Texas, it may be hot and humid enough to run without the temp switch to see what happens. The EPR valve and temp switch both have only one purpose, and that's to keep the evaporator from freezing up.

https://www.rockauto.com/en/moreinfo.php?pk=819375&cc=1036516&jsn=464
 
When I switched over in the '91 Daytona, I just purged and filled. Ran great for three years, no issues or any hassles. Of course the car was a beater, a great one at that, so why shouldn't it work perfectly!
 
Something to keep in mind: When converting to R-134, you are supposed to remove the EPR valve in the back of the compressor, and install a temp switch on the evaporator core to cycle the compressor on and off when needed. Chances are that the EPR valve is shot anyway. I bought three NOS EPR valves a few years back, and none of them worked. The temp switch is cheap, but getting the probe into the evaporator on a '65-'68 will be a challenge. Being in Texas, it may be hot and humid enough to run without the temp switch to see what happens. The EPR valve and temp switch both have only one purpose, and that's to keep the evaporator from freezing up.
I saw this same issue mentioned in a conversion article on the Original Air site but from other comments I've seen I doubt this is being done by everyone. The EPR valve seems to have been used on the big Mopar systems that did not use a cycling compressor before the days of smog tuning. Assuming the EPR works now what would happen if you just leave it?
 
My guess is that leaving the valve in will cause the A/C not to cool quite as well, since the valve is calibrated for R-12 and not R-134.
 
I took this car out to one of my Saturday cars-and-breakfast shows the weekend before last with some car buddies. The younger one (late 20s) had never ridden in a station wagon and had to climb in the wayback seat and wave at everyone on our way there. Had a good time and the car drove great. Three days later I went to move it and it wouldn't start, charged the battery but no good. Put in a good battery from another car and it fired right up so the 6 year old Interstate was junk. I had not bought a battery in while so I did some research as to AGM (Optima) versus traditional lead acid. Turns out all the major brands now have AGM alternatives but the long warranties that used to be common are gone. Now all the AGM's and quite a few regular only have 36 month free replacement warranties. I wound up buying a Duralast Gold size 27 from Autozone, it has 3 years free replacement plus two years prorated. Remember when some batteries were guaranteed for life? Good old days...

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What's the upshot re the AC?
Not much happening. I did check the system in more detail, all the controls work and send the air to the right place, compressor and clutch work quietly and the fans work in the rear unit but there is no cooling from either unit. I'm waiting for my shop to work me in but I have decided that I'm going to limit what they do to the very simple approach and see what happens.
 
Not much happening. I did check the system in more detail, all the controls work and send the air to the right place, compressor and clutch work quietly and the fans work in the rear unit but there is no cooling from either unit. I'm waiting for my shop to work me in but I have decided that I'm going to limit what they do to the very simple approach and see what happens.

Whether R12 or R134 things are not very complicated nor different. Since R134 already might as well stay the same. Dessicants for both are the same just so you know. The only issue would be the fittings for hoses and whether it is wired for a cut-off switch. Next there are R12 and R134 specific expansion valves but whether that makes a real difference is up to debate. I may turn my 91 Mazda into R134, or leave R12 as all is new or flushed, but the expansion valve is NOS 1990's Mazda and I won't concern myself with that.

Anyway when an A/C system isn't giving you cold air there can really only be one of two things wrong. Either you are out of refrigerant or your compressor is not compressing the refrigerant. That's 90% of the time. The other 10% is non-functioning compressor clutch, fan belt, fuses and pressure switches but not likely in our older models.
 
Whether R12 or R134 things are not very complicated nor different. Since R134 already might as well stay the same. Dessicants for both are the same just so you know. The only issue would be the fittings for hoses and whether it is wired for a cut-off switch. Next there are R12 and R134 specific expansion valves but whether that makes a real difference is up to debate.
What is a cut-off switch?
 
A cut-off switch prevents the compressor from engaging when it senses there is either too high a pressure or too low a pressure in the system to prevent damage. It works in conjunction with a sensor. They're typically included on R134A conversion kits.

There are also rpm related switches on newer systems to prevent damage from high RPM use.
 
A cut-off switch prevents the compressor from engaging when it senses there is either too high a pressure or too low a pressure in the system to prevent damage. It works in conjunction with a sensor. They're typically included on R134A conversion kits.
OK, I've heard of that on GM cars, nothing like that is mentioned in the shop manual for the 66.
 
Compressor wire runs to the sensor on the dryer first and then to the compressor. Sensor breaks the circuit when tripped and compressor can't engage. Not sure if it does high pressure too, but definitely low pressure.
 
I have decided I'm going to attempt the resurrection of my A/C system myself. The basic tools are not very expensive and will not only allow me to work on the Monaco but also service my other old car if needed. I have ordered a filter dryer and front expansion valve and picked up some small items like the conversion ports, o-rings, etc. I figure that it doesn't work at all now so I definitely can't make it much worse! Any tips are appreciated, I will post as I go.
 
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