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R12 to R134

Change the condenser as well when going from R-12 to R-134A. It was mentioned several post up but not in your picture shopping cart.

Since you are spending money and taking everything apart. What about swapping to the Sanden bolt in replacement compressor? They work very well and actually last.

I did the blue Ford orifice tube, O'Reilly's accumulator and condenser, new O-rings and a Sanden compressor on my 1987 dual a/c Suburban just a few months ago. 99° out yesterday. 130° in the truck when I started it up. It went down to just below 60° at the vent within a few minutes and stayed in the high 50's at idle. As soon as I got on the road it went to 45-48° and stayed there.

R-134a can and does work good in the square body trucks. I wanted to keep it R-12, but since I had to replace the locked up compressor and leaking condenser anyway. I went with the correct replacement parts and am happy.

Now, which cycling switch should be installed instead of the stock 1987 Chevy switch? That is a new one to me. I thought the GM switched had a screw adjustment between the to plug blades for that purpose. Mine cycles just at 42° when it is below 80° outside. The rest of the time it is trying to get down to that temperature engaged all the time. So, I haven't touched the screw to see what happens.
 
When you adjust the screw too far you can turn the evap box into a solid block of frost until no more air can pass. Then when you turn it off the truck leaks like a race horse. But maybe where you live the fan is never set to low. Usually when you talk about adding a switch it's a high-side cut-out switch. People install it with R134 conversions because R134 is mediocre and can have high pressures on the high side. But mostly it's a fail-safe to keep from venting if your fans fail or something.

Sanden compressors are nice, but keep in mind it's adding expense and complexity to reduce the cooling capacity of the system. I suppose a smaller pulley could compensate for the smaller displacement, but I don't know if there's any issues at high RPM. I understand the new AC Delco R-4s are pretty nice.
 
If you look at the stock R-12 condenser. You will see it is a big round tube that kind of just snakes around with a bunch of fins attached to it. R-12 was very efficient at getting rid of heat and the condenser was perfect for that.

R-134A doesn't shed heat as easy. It has to have more surface area to get the heat removed. So, a "cross flow" condenser is really a must when going to R-134A. I am pretty sure any replacement square body condenser you purchase new is going to be a cross flow. The tubing will be flatter and many more cooling fins.

If you don't change condensers then even if everything else is perfect. You might not ever get below 60° at the vent on hot days. That might sound ok, but with the sun bearing down, it will leave you wanted cooler.
 
If it is over 20 years old, it is inefficient cooling R134.
I too late with answer
 
This is what Rock Auto has... doesn't say R134a. Can you guys tell by looking at it if it's old style or new?

7013642__ra_p.jpg
 
That is the newer, R-134a friendly cross flow type. Notice how the cross tubing is flat and very densely packed with cooling fins?
 
That looks like the piccolo tube design, which is better than the original, but parallel flow is better.

The parallel flow one is 7-3642. It is not listed in your application, but if you check the OEM numbers, it will cross.
You can find mixed reviews on it, as well as the ACDelco one that is parallel flow.
 
3642 looks to have slightly different connections. Will it line up for me?

71uqR8Wg22L._SL1500_.jpg


6872xtc said:
That looks like the piccolo tube design, which is better than the original, but parallel flow is better.

The parallel flow one is 7-3642. It is not listed in your application, but if you check the OEM numbers, it will cross.
You can find mixed reviews on it, as well as the ACDelco one that is parallel flow.
Click to expand...
 
Looks more like camera distance as to the width of the fitting to each other. One is AN-8 movable hose from compressor and an AN-6 to the hard line to the bottom of the evaporator.
 
Mastiff said:
3642 looks to have slightly different connections. Will it line up for me?

71uqR8Wg22L._SL1500_.jpg
Click to expand...
I put a 3642 in my '90 A couple of weeks ago. It hooked up to the hoses fine, but as some had posted in reviews, (Amazon was one place) you have to move the mounts. I can't help you decide what route to take, as I am unsure if the piccolo tube design is a large amount less in efficiency. I discovered after I got the 3642 condenser, that I had a piccolo tube design one in my used parts stash...
I took it out of an '86 that it fit well in....

The Delco condenser has been good and bad in reviews that I found too...
 
The only advantage to tube style is that it can be flushed. I've heard of compressors blowing chunks when they die, but I think it's pretty rare. Has anybody done an A to B comparison where they had the stock large tube condensor on a square body (properly charged and running) and swapped it for a parallel flow one while changing nothing else?
 
I read the reviews on Amazon and don't want to bite off the frustration of non-fitting stuff. I did order the one from Rock Auto. Hopefully better than baseline and now's the time while I have everything apart.
 
So you got the piccolo tube design?

And I have had 2 of the R4 compressors puke metal in my '90. I know one was a parts house , Chinese unit, and the 2nd was used. It was quiet for 2 years, then in about 2 months,,,,,
I put an ACDelco on it now.
 
Mastiff said:
Yeah. I get that it's not ideal, but hopefully better than original factory.
Click to expand...
I definitely understand your decision.
If there was a known, perfect fit parallel flow condenser available, I may razz you though!!!

:rotfl:
 
Anyone know more about changing the set point of the switch? I am all charged up and working good on my '90 square but my compressor is cycling on and off too much. I have some parts to swap (condenser) but since it's working ok right now I would rather wait for next season to take it all apart if I need a different switch. It cools pretty good but I can improve it with some of the ideas listed here, I just don't like that compressor cycling so much. Charge pressures check out good for R134A.
 
HankScorpio said:
Anyone know more about changing the set point of the switch? I am all charged up and working good on my '90 square but my compressor is cycling on and off too much. I have some parts to swap (condenser) but since it's working ok right now I would rather wait for next season to take it all apart if I need a different switch. It cools pretty good but I can improve it with some of the ideas listed here, I just don't like that compressor cycling so much. Charge pressures check out good for R134A.
Click to expand...
Pull the wire plug off and see if there is a screw in the middle. I don't know which way to turn it though......
 
We pieced ac back on our 82 truck several years ago. I put a piccolo tube condenser on, junkyard hoses and a VOV. New compressor, dryer and I swear a new switch, but it says r12 on it- maybe I adjusted it-can't remember. BTW you can order a VOV on the internet for around $10. The AC works great with just one caveat. The hoses or evap. lose some charge over a season but not enough to track it. The ac will run you out of the truck and is wonderful after I crawl out of an attic. One other glitch I either didn't notice or or forgot about is that the belt isn't lined up with the crank and ps pump. I vaguely remember clutch compatibility issues and refused to buy a new one

One other thing, I couldn't find good conversion fittings and wasn't ordering internet parts back then. The low side fitting is not positive enough to leave the hose unattended. Check those real good before you charge. Also, I pulled a 500 micron vacuum on the thing for awhile. Auto zones around here rent a single stage vac pump but be advised that you might want to change the oil for a good vacuum.
 
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