Orifice Tube Install

[82DMC12]

Good to know. I have a variable one and just the plain regular GM one, deciding which one to install. I've read that owners that did install a variable one could hear a very noticeable whine in the system as the pressures changed.

I have the black GM variable valve in and I've never noticed any "whine" while driving. I can hear it bubbling when I park in my garage and shut the car off sometimes though.

[Ron]

Good to know. I have a variable one and just the plain regular GM one, deciding which one to install. I've read that owners that did install a variable one could hear a very noticeable whine in the system as the pressures changed.

If you are going R12, use the GM. I've never used a variable on a D...mixed stories, mostly not good....

[82DMC12]

If you are going R12, use the GM. I've never used a variable on a D...mixed stories, mostly not good....

I'd like to learn more about this subject. My A/C is "fine" but of course not as effective as my daily driver (Audi Q5). I'm not sure if the A/C can work any better than it already does. I've converted to R134a with a new compressor (Sanden SD5H14), a parallel flow condenser, new dryer, the VOV, and replaced all the hoses front to back with the kit from Hervey a few years ago. The only part that's original is the evaporator.

Is a single-orifice valve better? Also I heard there's a SD7 compressor that's "better" but how much better is not clear.

I'm going to open up my A/C next week for major frame service so now's the time for further upgrades.

[dmcman73]

I'd like to learn more about this subject. My A/C is "fine" but of course not as effective as my daily driver (Audi Q5). I'm not sure if the A/C can work any better than it already does. I've converted to R134a with a new compressor (Sanden SD5H14), a parallel flow condenser, new dryer, the VOV, and replaced all the hoses front to back with the kit from Hervey a few years ago. The only part that's original is the evaporator.

Is a single-orifice valve better? Also I heard there's a SD7 compressor that's "better" but how much better is not clear.

I'm going to open up my A/C next week for major frame service so now's the time for further upgrades.

One other piece of info I was told when converting to R134a, from some other owners, was to adjust the low pressure switch using the screw that is in-between the prongs of it. The right way would be to adjust it using pressure gauges (I don't remember the specifics), or, a generic way is simply turning it one full rotation counter clock wise. It supposedly helps a lot.

[Bitsyncmaster]

I'd like to learn more about this subject. My A/C is "fine" but of course not as effective as my daily driver (Audi Q5). I'm not sure if the A/C can work any better than it already does. I've converted to R134a with a new compressor (Sanden SD5H14), a parallel flow condenser, new dryer, the VOV, and replaced all the hoses front to back with the kit from Hervey a few years ago. The only part that's original is the evaporator.

Is a single-orifice valve better? Also I heard there's a SD7 compressor that's "better" but how much better is not clear.

I'm going to open up my A/C next week for major frame service so now's the time for further upgrades.

One thing I found that really improved the AC cooling is to open that condensation drain. The OEM design has that elbow crimped I guess to try to reduce air flow loss but it makes the drain plug up and the water in the evaporator box blocks air flow over the evaporator.

I removed the OEM drain and did the "Bill" fix to use a coil boot. I added a normal elbow to a hose running to a drain hole drilled in the floor. That also keeps the water off the frame.

[Ron]

I'd like to learn more about this subject. My A/C is "fine" but of course not as effective as my daily driver (Audi Q5). I'm not sure if the A/C can work any better than it already does. I've converted to R134a with a new compressor (Sanden SD5H14), a parallel flow condenser, new dryer, the VOV, and replaced all the hoses front to back with the kit from Hervey a few years ago. The only part that's original is the evaporator.

Is a single-orifice valve better? Also I heard there's a SD7 compressor that's "better" but how much better is not clear.

I'm going to open up my A/C next week for major frame service so now's the time for further upgrades.

My experience and research over the years: R134a has a lighter molecular size, lower heat transfer rare, requires a larger condenser, runs at higher pressures, and results with ~5°F lower output air (in a D)...~15% less efficient.

The only reason I know some use variable orifices, in a D, is because of R134a's higher pressures.
The Saden SD5H14 & SD7H14 have a good rep - Beware of knockoffs!

Seems your setup should be OK for KS,
(R12 would do better, but you would have to use a quality flush and a different type oil....)
Generally, a system is OK if:
70°F, 20% humidity, 35-40°F at vent...
80°F, 90% humidity, 45-50°F at vent.

[David T]

The best advice is to try to stay with R-12 as long as you can. The system was designed for it and any other refrigerant is not going to have the cooling capacity of -12. If you can't get -12 the next best choice is R-414b. It is a drop-in blended replacement but should not be used in a leaky system because you can only "top off" twice, after that you mess up the blend proportions. Finally we have -134. To use it you must flush the system, change all of the hoses and "O" rings, drain the oil from the compressor and refill with the correct stuff, change the service ports and accumulator, and adjust the low pressure switch. After all of that you lose about 10% of your cooling capacity. In a place like Florida you will notice it on a really hot day.