A/C Upgrade '85 Suburban w/ Rear A/C

[TRAZOII]

Hi all,
Im looking to upgrade my Ac system.

I currently have an R4 "Pancake" Compressor.
The system has been disconnected for over a year. Seeing that it has rear AC I know there will be alot to refill. Not 100% sure on refill amount or oil amount.

But Ive been told to upgrade my Compressor to a Sanden. So Im looking for the brackets and or the Refill amounts with R134A.
Im not really A/C savy so any and all help will be greatly appreciated.

So here is the stats.
1985 Chevy K10 Suburban
SBC 350. Alternator is on the Passenger side.
AIR pump deleted.
Ac located on Driver.
Factory AC with Rear AC

[75gmck25]

I used these two items to replace the old A6 compressor on my '75.  It all bolts on and fits very well.
https://www.summitracing.com/parts/vta-15123-vcb
https://www.summitracing.com/parts/vta-04808-vua

I had new custom hoses made with the connections for the Sanden, but I believe Vintage Air also sells adapters that would let you connect your orginal hoses to the new compressor.

The general rule of thumb is to use R134a charge is that approximately 75% of the recommended R12 charge.  For example, on a big system like yours they might recommend 80 oz of R12, so you would use 60 oz of R134a.

I also used a Ford blue orifice instead of a GM white orifice (supposed to work better), and completely flushed the system so I could switch to PAG 100 oil.  You also need to replace the accumulator or filter/dryer.

Bruce

[Oldblue]

A few more general things I would recommend.

Here is the order I would do things

1. pull vacuum on system and remove oil. (You may need a shop to do this, but maybe someone else has an idear)
2. Replace the ac compressor and update hoses or use adpapters for r134a
3. Install new dryer and seal system. ( Do not open the new dryer or uncap it until you are ready to install as some can be useless in 24 hours if left out depending on where humidity etc..)
4. If needed add oil ( most compressors come with oil in them, but do not forget this! If your system has no oil and you just charge it the compressor will fail). I imagine sanden has specs on this or information.
5. Charge the system yourself or have someone do it.
6. A system working properly should be around a 20 degree F drop.
7. Enjoy the cool air and your handy work.

Hope that helps. I also bet with some google searching you can find the r12 to r134a specs you need, but I bet you can find some generic information on youtube to help give you better understanding and confidence too if needed. Even if it's not the same vehicle often the concepts are the exact same. Convection principles are convection principles...

 

[75gmck25]

OldBlue has the procedure down, but I thought of a couple other things you need.

Get a package of R134a O-rings (they are usually green, vs. the older black o-rings), and replace all o-rings on the fittings.  Most auto parts stores have a small package of o-rings that has all the sizes you need.

Manufacturers used about 3 different lubricants inside A/C systems over the years, but current systems almost always use PAG oil.  In general, you don't want to mix oils in the system, since incompatible oil sometimes forms more of a sludge than oil.  However, since you are replacing the compressor and filter/dryer, you can just take all the hoses apart (replace o-rings) and use A/C flush to remove the old oil from the evaporator, condenser and hoses. 

My Sanden compressor came pre-loaded with oil (4 oz?) and I think the specs said SP 15.  Despite the number differences, SP 15 is supposed to be about PAG 80, and the closest match they sold in local parts stores was PAG 100.   I added an additional 3-4 oz to replace the oil in the condenser and evaporator, for a total of about 7-8 oz.

Bruce

[VileZambonie]

Before you go dumping a bunch of money into it, test the system. Do you know why it was disconnected? Where was it disconnected?

I would charge the system with Ester oil containing dye tracer (capacity is 6oz) and the system refrigerant capacity is 84oz so initial R134a charge should be about 76oz

[Oldblue]

vileZambonie makes a great point. I have been assuming you know what needs to be replaced. If you don't and you are taking what some else told you and running with it then I would not do that. I believe pag oil also comes with the dye in it or it can (at my old shop it did), but other wise for me when I redo my ac everything is getting replaced. hoses, compressor,condenser, dryer, evaporator, heater core and all the pluming.

Unless it's new I don't trust 30 year old ac parts unless you're budget constrained and have to.

On the flip side I have bought cars with sealed systems that haven't had ac for a few years and slapped a new compressor and dryer in and was good to go. I think the point Vile is making is just make sure you don't have other parts that need replacing etc.