Automotive Air Conditioning Information Forum (Archives)

300zxer on Fri September 03, 2010 12:55 PM

Year: 1986
Make: Cheverolet
Model: Suburban
Engine Size: 350
Refrigerant Type: r12

I have an 86 Suburban that I have had since new. Three years ago, I restored it, except for the A/C. I am trying to decide what to do. I can either chase the leaks in the front and rear evaporators/hoses, replace the compressor & drier, etc and recharge with r12 or 134; or, block off the back evaporator and hoses, replace the compressor and recharge with r12 or r134. I have heard that r134 in the old Suburbans doesn't perform that well. What happen if I block off the rear evaporator and hoses, will it perform better in the front with r134 since the condenser will be over sized for the smaller system?

Dougflas on Sat September 04, 2010 5:39 AM

You need more AC capacity due to the large volume of the vehicle. Keep both evaps and stay with R12 is what I would do.

300zxer on Sat September 04, 2010 10:06 AM

How would you go about leak detection on a system that size? Use a sensor or dye or both? I must admit I am a little overwhelmed by the number of connections and length of hoses. I also hate to waste any r12 to pressurize the system for leaks. Are there any refrigerant saving ways, like nitrogen with dye.

1stbscout on Sat September 04, 2010 12:38 PM

If you are not going to run the system you could use 134a to test for leaks. Evac system and check to be sure it holds vacuum then liquid charge the high side with 134a. Test for leaks after it has set out in the sun for long enough to drive pressures up using a hand held leak detector. Other than that I am not sure what to suggest.

Dougflas on Sat September 04, 2010 5:25 PM

if you have nitrogen, you could put an oz or two of r12 in the system then add notrogen until you have a pressure of 50 to 75. Use an electronic leak detector. Or as mentioned, you could use r134 and nitrogen. R12 will indicate easier. Take your time and check every connection. Try to do this in a garage so the wind doesn't affect you.

300zxer on Sat September 04, 2010 8:40 PM

I like the idea of pressurizing with r134. I hadn't thought of that. I'll put the can in a container of hot water to get the pressure as high as I can before I start checking. The back evaporator will be easy to sniff. The front I can only check by running the fan or sniffing the drains. I am of the opinion that if the lines and connections checkout OK, I will probably change out both evaporators, to be on the safe side, and also change out the drier, schrader valves, compressor and orifice tube. Since I have had the truck since new and just recently restored it, I plan to keep it in the family for a while. It isn't worth anything to anyone, but my family and the investment is worth it to us. I just want to make sure the leak isn't in one of the lines.

Dougflas on Sun September 05, 2010 4:23 AM

you can sniff the front evap by getting to the drain hose, removing blower motor resistors, or by removing the fan motor on a lot of vehicles.

300zxer on Sun September 05, 2010 8:29 AM

Dougflas, thanks for the input. I'll let you know how it goes.

chris142 on Sun September 05, 2010 4:33 PM

Those Suburbans and Pickups just will not work on R134a. These need to stay R12.