Automotive Air Conditioning Information Forum

Year: 1989
Make: Chevrolet
Model: G20 (full size van)
Current AC: R4 with R12
Front air only (no rear)
Serpentine belt on steel mounting brackets (steel used in 88, 89, and maybe 90)

About six years ago, I installed a new R4 compressor on my full size Chevy van. I thought all the leaks were repaired but apparently not. It works fine for the summer but by the next summer it needs to be topped off again. R12 just doesn’t seem like a viable option for me anymore. For the last two summers I haven't used the air and that's no fun in the South. The backstory is that the AC in this van has never worked "well" in around town driving. It's been that way since new (when I bought it).

Now seems like the time to switch to R134a. If so, then I will replace the accumulator, orifice tube and the condenser. Unless someone knows of a drop-in replacement parallel flow condenser it seems that new refrigerant hoses might be required. It might be smart to replace the fan clutch too.

The question is will replacing the compressor improve the AC performance? If yes then now would be the time since most of the front end of the van will come off to replace the other parts. I have tried to read everything I could about replacing the R4 with a Sanden, Seltec, V5 or V7 compressor. All seem to have pulleys with a 119 mm diameter. The plus for the Sanden and Seltec is that a R4 conversion bracket exists. If there is one for the V5 or V7 I haven't found it. Fabricating a bracket for the V5/V7 is not the problem. It's designing the bracket so the pulley is in the correct location that's the problem. It seemed like the Sanden or Seltec would be the clear winner. That's until I saw the performance graph for the V5/V7 that bohica posted in the link below.

https://autoacforum.com/viewtopic.php?t=183

Sanden has performance graphs for the SD7H15 and the enhanced SD7H15 at the links below.

http://www.sanden.com/objects/SD7H15_Performance.pdf
http://www.sanden.com/objects/ESD7H15_SES.xls.pdf

From my reading of the graphs here are the results at 1000, 2000 and 3000 rpm compressor speeds:

Cooling Capacity [kW] 1000 rpm 2000 rpm 3000 rpm
V7............................. 4 ........ 8.5 ........ 12
V5............................. 3+ ....... 7.5 ........ 11
SD7H15 Enhanced.......... 3+ ....... 6.5 ........ 9+
SD7H15....................... 3 ........ 5.5 ........ 7.5

How would the R4 compare with these four compressors? From the numbers, at 1000 rpm the V7 produces 1 kW (~3400 Btu/hr) more cooling than the SD7H15 or 33% more. And it continues to outperform at higher rpms. The V7 looks great on paper but is this a case of "lies, damn lies and performance graphs"? So much for the theory. How do V7s perform out in the real world? Why aren't V7s used "everywhere"?

Thanks,
Steve

They are a solid performer, just overlooked.

As a replacement for the old Mopar V2 I had outstanding performance. As long as you get the right control valve it works just like the EPR did in the OEM Mopar install.

If you have room for it, it should be far better than the R4 in terms of reliability, and on part with displacement. Much smoother too, with no cycling.

Why GM put them on a 4 cylinder S10 with a tiny cabin is still a mystery to me. Perhaps it was part of the CAFE stuff to keep the efficiency in the sweet spot.

Thanks for the response. The variable displacement compressor makes a lot of sense to me. I'm willing to try it if I can figure out how to mount it.

I'm assuming you don't have a performance graph for the R4 to compare with the V7. From your experience do you believe the V7 is worth the extra effort to get it mounted?

Do I assume that I'm on my own when it comes to a mounting bracket for the V7? The link below shows an owner fabricated bracket for a V7 retrofit on a LandCruiser. So far that is the best I have found.

http://www.autoacforum.com/messageview. ... adid=23731

When mounting does the crankcase plug need to be at the bottom or within so many degrees of vertical?

The control valve choice is a mystery to me. The green valve is rated at 37.5 psi and next is the yellow at 40 psi. Is there a commonly used control valve? Is there a guideline for choosing the control valve? I'm a little surprised that the control valves are offered in 1 psi increments from 40 to 45 psi. Assuming the evaporator doesn't freeze, is there a noticeable difference between a 40 and a 41 psi control valve?

On the ackits.com website I haven't been able to get their filters to work. I wanted to see the mounting options (ears vs direct mount) for a six groove pulley for just the V7 compressors. I'm assuming that mounting ears might be easier than a direct mount.

Thanks,
Steve

Here is he ear mount compressor:

[url]http://www.ackits.com/comp-v7-pv6-3274[url]

You should call Tim at AC Kits about control valve options.

If you are looking for a core unit for mockup work at the junkyard, 98 to 03 S10 pickups with the 4 cylinder engine.

V-7s and V-5 need to be mounted with control valve at 6 o'clock or near that-- 5 to 7 o'clock will work-- it is for oil splash inside the crankcase. A V-5 will do as good as the V-7 in my opinion. I have seen too many V-7s run low on charge and burn up inside on the S truck application-- I usually replace them with V-5s since they are cheaper and much more common and fit in same bracketry with a slight tweaking. Through bolts instead of threaded holes etc.

Control valves are of different specs due to suction line length- find a suction line length application near the same distance from evap as you plan to install and use that color control valve. The whole idea is when to de-stroke based on evap freeze avoidance. You want a valve that destroke the compressor right before evap hits 32 degf.

I'm still assuming the ear mount will be a better choice than a direct mount. I have access to machining and welding tools if that makes a difference to the mounting choice. I'm not looking for more work, just less aggravation overall. The simpler the better.

Tim sent the following link to all the V5/V7 compressors: http://www.ackits.com/80-v5 . At this point I believe either the V5 or the V7 will be much better than what I have now. The choice between the two might be other features. Looking at the compressor stats and photos on ackits, RockAuto and Ebay, are there any V5 compressors with more than three mounting ears? The V7 in the 98-03 S10 link from Bohica appears to have four ears. Not knowing how it will mount, more ears seems like more mounting options.

Of course it needs a six groove pulley. Are the pulley diameters all the same at 124 mm?

On most of the compressors, the S&D port location is the usual GM pad out the back. The Cadillac Caterra and Olds Intrigue compressors have a radial facing pad. I don't know which would be better. In the 89 Chevy van the accumulator is forward of the passenger side mounted compressor by a foot or so. The current suction line includes some purpose bent steel tubing attached to the compressor and accumulator ports with hose in between. The total length is ~36" and the flexible hose is a little more than half of the length.

For a high pressure cutout switch, does it matter if it is a high pressure cutout switch or a binary switch? If I understand correctly, the HPCO switch would open at say 400 psi and close at 300 psi. The binary switch would do that and also open at say 28 psi for a low pressure cutout. In my case, could I use the clutch cycling switch to act as the low pressure cutout instead of the binary switch? The FSM says that clutch cycling switch will open at 21-24 psi and close at 43-49 psi. Mine does have the adjustment screw if that makes a difference. Would this switch interfere with the V5/V7 control valve?

Thanks for your help.
Steve

Think a rear-exit V5/V7 would be easier than the top port type. Only because I did a water pump on a '90 G20 last week, it's kinda cramped in there.

Didn't see a HPCO on that one IIRC they didn't get one from the factory until R134.

The low side pressure control with a V5/7 is the control valve in the compressor. It's a good idea to have a LPCO to prevent compressor operation in low charge / low ambient conditions. I have a retrofit V5 application, using a GM #115144494 switch for the LPCO. Cuts out at 18psi so it leaves enough room for the compressor control valve to be the primary low side pressure control.

One answer to my question about a four eared V5 with a six groove pulley is the 94-97 S10/Sonoma.