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Discussion Starter · #1 ·
Hi All,
I recently completed the overhaul of my AC system and thought it might be good to share my research with ya’ll.

So to recap, I have a 1983 4 door RRC with a 3.5 Carb engine (now running Sniper EFI throttlebody) which is ‘rescued’ from a junk yard in Houston. The car is an original US import (was registered in Texas in 1983 with 12miles on the clock) has as factory AC.

When I got the car more than a year ago there was very little residual gas pressure and I simply pulled a vacuum and filled it with Envirosafe which is a replacement gas, I corrected all the wiring and presto I had cold air.

This worked fine for a year, but I noticed an oil streak was starting to form around the compressor clutch indicating the compressor was leaking from the shaft seal. At some point it was out of gas, thankfully this was winter time in Houston so I had time to study a fix.

The compressor used on an 83 is a Sanden 508 with double a double groove V-belt. These are readily available either as a cheap replacement, a rebuild or original Sanden. I could have overhauled (you tube examples plenty) but decided to a purchased a new Sanden compressor on Amazon (Vintage Air 04808-VUA Double V Groove 508 Compressor) for $189.99 free shipping etc. Came from Austin nice and quick.

So far so good, but then I then noticed that although the compressor is the same the back plate where the hoses connect is very different. I basically received a R134A compressor with different size fittings and no hi/lo service ports. I could have returned and sourced a R12 unit, but since one of my hoses had what looked like a repair, I decided instead to change the hoses/fittings and persevere with the R134A compressor.

While I was fixing myself up with hoses and fittings, which it turns out are very nicely standardised and easy to get I decided to get the crimp tool and do it all at home (I already have the gauges and vacuum pump etc).

Hose situation under control I figured out that I had to look into my oil situation. My car had R12 using mineral oil, my Sanden compressor was filled with PAG oil. Both oils are not compatible. Basically, the R134A gas will not dissolve in mineral oil and thus will not be transporting the oil around the system. There are two solutions: 1) clean everything of the mineral oil (ideally with a solvent) and proceed with PAG oil or 2) use an Esther oil which will allow for some mixing (quick and dirty way). Sanden warranty requires PAG only so that tells you enough.

I decided to flush my system with PAG oil instead. PAG oil is not too expensive and my system was clean so I just pushed 10-odd OZ through the Evaporator and Condenser till it ran clean (dryer was changed with new). I then blew air through for a while to remove the excess oil.

For the oil refill I estimated the amount of oil in the system and then used the suggested compressor fill of 3oz (basically you drain some oil from the compressor as they come filled for a new clean system)

I also changed the o-rings with the green type.

I changed the dryer and found the fitting for the Trinary Switch was different so I bought a new one (for R134A) which has the following characteristics: 30PSI low cut out, 242PSI fan kicking in and 377PSI high pressure cut out.

All ready I vacuumed and filled with three cans of R134A (Walmart $4.99 each) 36 oz. It is not very warm here now (70F) but my pressures are about 30 on the low side and 200 PSI on the high side. Vent temp was about 40F.

I found a bunch of information on the web from Land Rover. In particular Technical Service Bulletin # TEC82019:

Date: 970314 A/C System - R 134A Conversion Kit

MODEL Range Rover Classic Defender 110

87-94 R-12 Systems

This also provided the volumes (which I presume to be the same for an 83):

Refrigerant R-134a • Range Rover - 1.05 kg (2.25 lb)

ESTER Refrigerant Oil (NOT PAG oi)l • Range Rover - 150 ml (5 fl oz) - note the instruction assume you convert without a full flush, hence use of Ester oil -

Auto part Engine Vehicle Fuel line Car
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Auto part Fuel line Engine Vehicle Pipe

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the last picture shows the flushed oil from initial Mineral (brown) to eventually clear (PAG)

I hope this information can be of use to anyone in the future.

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