Thread: Any A/C experts out there?

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Originally Posted by DennyW

Mike, that sounds like R-12 at 2500 rpm's, fan in front of the condensor readings.

no, i got those # off of a 1996 caddy that a new comp. (low side was 30)
was installed on last week, and i called the shop to see how it was doing sense it had cooled off some and he said it had been cooling great, but he hadn't checked the pressure anymore. it pulled down to about 50 degrees. if stu had a cooling problem i would agree with a restriction, but, 38 degrees ???? you should have cooling problems with restriction like "no cooling"

I was hoping that some one would say that.

I do not remember seing a stuck, sticking or clogged expansion valve that allowed the evaporator to cool enough to blow cold air out the vents.
Not saying I never came across it, but right now I do not remember such a case.

I still would like to know how much fluid was put into the system, and how much of that damn dye.

The dye could be a factor. We did not weigh the supply tank, only going by gauges to determine the amount. Next time we will use a scale. I will find out how much dye went in tomorrow, it was put in by the first shop that worked on it when we were chasing leaks. So the consensus is if the expansion valve was partially clogged it would not cool at all?

thanks again for all the help

Pat

It is a simple thermodynamic principle. Your a/c system is a heat mover. For the evaporator to remove heat from the vehicle, a defined amount of fluid must pass through the valve and then the evaporator. This fluid will move the heat from the vehicle and expell it.

When the a/c system "blows cold air," it is removing heat. For the system to remove heat there must be a sufficient flow through the expansion valve or orifice.

Restricted valve or orifice and no fluid flow and thus no cool air.

Thanks again everyone, I will refrain from using the A/C until this is resolved. I spoke with the folks at Southern Air, they are the ones who built the original system. He agreed there is a restriction and indicated the small fitting may be the problem. My next step is to pull the hose with the narrow fitting and have it redone with a proper one. This will have to wait a little bit as my buddy with the gauges, vacuum pump and 134a tank is going out of town for a while. While I have the system apart I will look for other restrictions and make sure everything is clear. I will also look into this stuff:

http://www.acsource.com/index.asp?Pa...OD&ProdID=1245

And may flush the system depending on how far I need to take it apart, per the instructions. We will weigh the tank as we charge, I have a fishing scale that reads in pounds and ounces, and set the target for 2 pounds or less. The Southern air folks said the pressures are the ultimate measure as the vairied size of systems makes it difficult to predict an exact weight of 134a to use.

Just like other experiences, I am sure learning a lot about auto air conditioning works and I thank all of you for taking time to share your knowledge.

Pat

Thought I should wrap this up and let you know what happened with this, thanks again for all the replies. We got the system working right last week-end. Basing our actions on the idea that there was a restriction in the system, we removed the refrigerant, then flushed the condensor and evaporator and made sure the hoses were clear. We then vacuumed it for over an hour at 28+ inches and checked to make sure it would hold the vacuum. Then we slowly applied the refrigerant, this system has always been R134, was never R12. We did not have a scale to measure how much we applied. The pressures came in just like they should and we ended up with just under 30 on the low side and 190-200 on the high side. We had to set a fan up to blow through the condensor to get the final pressures just right. It is blowing 35-36 degrees with the fan on high now. The odd noises are gone and it seems to be working like it should. We believe there may have been residual oil and/or dye in the system and flushing it has solved the problem. So Stu Cool (that's the Studebaker's name) is indeed cool as it should be!

Pat

Yeah I think the only thing I would worry about is frying the compressor. You should also add an ounce of oil to the evap and condensor.

You got such good advice on your A/C I have a question

I want to put a A/C system back in my 1977 Chevy C10 truck
It originally had A/C I would like to use R134 I have the old R12
pump but it is bad What is the best way to go about this

Ron 52

I have changed over a few of my Avanti s to r134 -you minimal have to change out receiver /dryer, o-rings completly flush system w/ cleaner to remove traces of old oil . Install new compressor w/ ester oil, charge to ~ 80% of r-12 capacity- better to go by weights. If you do not change all hoses to " barrier hose" you will have to top off ever 6-10 months as r-134 partical size is much smaller than r-12 and w higher r-134 static pressures will seep out through walls of hoses. 31 5w