Automotive Air Conditioning Information Forum (Archives)

krauseas on Wed September 01, 2010 12:58 PM

Year: 1987
Make: Jeep
Model: Cherokee
Engine Size: 4.0 L
Refrigerant Type: Convtd to 134a
Country of Origin: United States

I have an older model (1987) Jeep Cherokee that had engine rebuilt about 5 years ago and my son still drives and likes this vehicle.

When the compressor seals went bad on this vehicle in late 1990's, I put in a rebuilt compressor (Sanden 508) and drier, flushed the system, and converted it from R-12 to R-134a. It always worked pretty good, but not as well as I would have liked because the components were designed for R-12 and not R-134a.

Now the compressor seals are pretty much shot again and it is time to replace it (at least before next summer). Does anyone out there have advice or experience with this type vehicle around possibly changing to a different condenser that might improve the overall performance on R-134a? Existing condenser is a basic serpentine tube design. I looked at the mid 1990 model Cherokees with the same engine that were, of course, designed for R-134a, and noted that they were supplied with a different parallel flow condenser. Of course, they also had different compressors that I'm sure were also matched to the system for R-134a, so I'm not sure that changing the condenser only would give much marginal improvement. I would also consider changing the compressor, however, only if I had one that used the same mount configuration. That may be difficult to find.

Any experience with a converted Jeep Cherokee?

TRB on Wed September 01, 2010 1:49 PM

You will need to make up some hoses but this condenser will work in the area available.

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Edited: Wed September 01, 2010 at 1:49 PM by TRB

krauseas on Thu September 02, 2010 5:50 PM

Thank you. By only adding the more efficient condenser, do you think I will get a noticeable improvement in the overall system?

iceman2555 on Thu September 02, 2010 7:53 PM

Replace the 508 with a comparable model SD7H15 compressor. Works better with 134a. In conjunction with the new condenser and the correct charge..should cool this vehicle very well. The 508 was never designed to function with 134a.

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ice-n-tropics on Fri September 03, 2010 11:18 AM

Welcommen
The 1987 SD508 had NPR seals and a axial mechanical face shaft seal which were not optimized for R-134a.
The remanned replacement has dubious specs'
New SD508s built in Singapore has HNBR seals and a shaft lip seal making the SD508 optimized for R-134a
SD508 = 138 cc swept volume displacement.
SD7H15 = 154.9 cc disp
Drive ratios may change due to clutch diameter difference which can result in more displacement per mile
Therefore a change to SD7H15 needs more condensing capacity due to more displacement to pump more mass flow of refrigerant.
If drive ratios were the same, then needed additional capacity = 12% disp increase + 30% X 12 horsepower energy = 16%
Change to R-134a from R12 needs about 10 to 20% more condenser
Without drive ratio increase, total condenser capacity increase needs to be + 30% for change to R-134a /SD7H15
A pusher electric fan in front of the condenser is a + for low speed operation
hotrodac

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Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
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