[V8] Losing faith - A/C issues

[Professor GT gmail]

Roger,

One of my compressors is actually a Toyota compressor (Nippondenso). I have taken a photo of the ID tag on it for reference, but I haven't taken the time to compare all three compressors that I have. One is from a 90, and the other two are from  91s. If the Denso compressor is the same as the others as far as mounting, connections and so on, it should be easy to cross to a common part that will fit.

I would not recommend buying a new one because that's just highway robbery (pun intended) even at the seemingly bargain basement price of $500. To me there are too many other viable options to keep you from going broke, and when used units are going for $1-200 that's the smart choice. 
Personally I would check the replacement unit over before installing it, but then again I do this from the vantage point of a trained eye.

If the pulley spins smoothly on its bearing that's the first step. Next, have a look at the refrigerant line connection points first to be sure there is no damage that will cause the lines to leak when connected, and secondly look at the oil that is there and that comes out when you tip it up. If there are metal particles, or anything black coming out, PASS on that one and ask for another. If you wanted to be extra sure you could rebuild a good core unit, but it would take se doing to get the rebuild parts, and to secure the proper tools to do the overhaul. Factory manuals from most makes used to cover compressor overhaul quite well. In fact in A/C classes we used to cover it, but like most components today, the flat rate greed factor, among other things has made this skill a thing of the past.

Lots can happen to a A/C compressor during its life, but for the same token if the vehicle never had its A/C system opened up and it was properly serviced, the compression can last a lifetime. The problems start when improper service procedures are performed, or a system sits open for a length of time, for any reason. Since pre-95 vehicles like our V8s were designed for R-12, and that stuff is long gone, most have been converted to R-134a.

That's typically when the games begin! 

I finally got around to putting a new (used) engine in my V8 last Sept. I bought a '90 from a guy who posted his car for sale on the forum. I got lucky, as I got the whole car for $350! (It was hit lightly in the right rear, but the engine has proven to be in very good shape.)
I just got around to finishing the A/C work about 2 months ago. I replaced the accumulator, the fixed orifice tube, and ALL the o-rings in the system. I filled it with R-12, or at least I attempted to, but I ran short by about one pound, so I sucked it down and then converted it to 134a. The cooling performance is better than I expected, but still not as good, obviously, as R12. With the differences of the R134a molecule, larger evaporators and condensers are necessary to get comparable performance to R-12. 

Now, the point is that by following proper procedures, I was able to use the existent compressor, which I never saw work prior to this point. It checked out okay. I replaced the mentioned system parts (critical) (the fixed orifice tube had a few metal shavings in it which was unnerving, but it was no where near clogged so I continued as it is "normal" to see some trash in the tube even with a healthy system, AND once all those parts were in place (accumulator goes in LAST so it doesn't absorb too much moisture) I put the system into a deep vacuum. Since there was no refrigerant in the system, a good old fashioned vacuum pump was used. Now, here is where most guys fall short.  The vacuum pump is used to evacuate the system, prior to charging it with refrigerant, and many techs simply go no further. However, it is used to leak-check the system, and to boil off moisture, and there's the rub: the length of time needed to boil off moisture is dependent upon how much moisture is present. Pulling a vacuum for a half hour may not be enough. Not even an hour may do it! In my classes I would demonstrate pulling a vacuum on a glass beaker with water in it. The water will begin to boil at room temp due to the vacuum, but the moisture in the system is not "gone" until ALL the moisture boils off. That can take some time, so patience is a virtue here.

Most general recommendations say to leave the system on the vac pump for 45 minutes. Well this is one of those times when more is good, as it certainly won't hurt anything to go longer. I've even left the pump on vehicles over night if it was convenient, and it was a system I knew was exposed for an extended time. The pump should also be shut down and left connected to see if the system leaks down, obviously indicating a leak. Moisture degrades performance, and more importantly forms acids which eats the system from the inside out, so it needs to be gone - nuff said!

Other things like lubricating the o-rings with refrigerant oil prior to installation to prevent tears, and adding adequate oil to the system are critical to proper system performance and longevity.

Charging the system with a scale to assure the correct amount of refrigerant is added, and just as important, to ensure it is not overfilled, is another important measure. It's the difference between doing a hack job and a professional job. "Paying Customers" deserve nothing less than a truly professional job, but unfortunately "Flat Rate" (Greed) in most cases is diametrically opposed to quality.

On my particular vehicle I had to repair poor connections at both the high pressure switch located at the bottom of the condenser, and at the ambient temp sensor out in front of the condenser. They both suffered "pin spread" and "fretting", and once good connections were reestablished the system began working properly with no remaining codes.

I have been enjoying the past two months with cool and dehumidified driving (and clear vision as well - no fogged windows).

The compressor has been performing well and is not noisy. Life is good!
 
Keep us posted on you progress!

Thanks,

ProfessorGT
(Sent from my iPhone4)