Refrigerant Control Valves

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Replacing An RCV 

By Ignacio (Nacho) Corella

Your customer comes in com-plaining that their car’s A/C losescooling at idle or that they have

to rev up the engine to get it to cool. Youthrow on the gauges and find that thesuction is up or discharge won’t move;obviously, the compressor needs to bereplaced. But does it?

In many cases, with a fixed-stroketype compressor, that may be true.However, if the car or truck uses a vari-able-stroke compressor, there might beanother reason for the decreased per-

formance.Many GM vehicles use a variable dis-

placement compressor, which is alsoknown as the V5 and V7. Some of themodels using them are the Cavalier,Malibu, Cutlass Ciera, Century, Sunfire,Venture Minivan (up to 2000), S10 truckswith 4-cyl engines and dozens of othersgoing back to the mid 80’s and up to cur-rent production. More frequently, you’llalso see this performance problem inVolkswagen products using the SandenSD7V16 compressor, dating back to theearly 90’s and through today. Note that most variable displacement compressorsare used in smaller, 4 and 6-cylinderengines; larger GM V6’s (like the 3.8 or4.3L) use a fixed displacement compres-sor. Another common variable strokecompressor is Nippondenso’s 6C17 usedby Chrysler between 1992 and 1989 inmany of its V6 minivans and sedans.

Instead of a failed compressor, thecooling loss is due to a faulty Refrigerant Control Valve (RCV). The symptoms are

suction pressures above normal, any-where from 45-80 psi, while the dis-charge pressure remains somewhat nor-mal. Air from the vent is merely “fresh”or even somewhat warm.

The RCV is a more sophisticatedmethod of controlling A/C system operat-ing pressures. It works by adjusting, actu-ally optimizing, the compressor’s pistongear traveling stroke, by determining thecompressor’s internal refrigerant pressure(inside the compressor’s housing). RCV’s

are spring-loaded, pressure-sensitive

devices that sense the compressor’s inter-nal pressure and “push or pull” the pistongear or increase a swash plate angle,depending on the compressor’s type.

The main reason for using a variablestroke compressor is that it is a more effi-cient pump; it reduces fuel consumptioncompared to conventional compressors.

  Additionally, if working correctly, thesecompressors also allow for a smootherengine operation as they never cycle onand off, something that is annoying tomany drivers. Conventional systems

(fixed stroke) use thermostats or low-pressure cutoff switches and compressoroperation is intermittent.

GM systems equipped with variablestroke compressors do not have a lowpressure cut off switch and they can runwith as little as 15% of the system’scharge. They do, however, have switchesto cut the compressor off if a high-pres-sure condition is detected. This may dis-concert the driver because they willnotice their compressor is still running yet 

no cold air comes through the vents. RCVfailures won’t keep the compressor fromrunning either. If it quits, the compres-sor’s ability to move the refrigerant insidethe system is just reduced. On the otherhand, VW systems, with the SD7V16compressor, shut the compressor down if a low-pressure condition is detected(thanks to a trinary switch in the drier).

Replacing the RCV is not a big job inany of the applications. But better yet isthat the compressor, with some minormodifications, can work just fine without 

the RCV (if perhaps you get stuck andcan’t find a replacement).

VERY IMPORTANT: The A/Csystem must be dischargedbefore attempting thisrepair—always wear safetygoggles!

In GM products with the V5 and V7compressors, the RCV is located in therear cover of the compressor, and lookslike a nipple on the outside (Photo 1). It’sheld in place by a snap ring and lookslike spinning top (Photo 2). In most or all

FWD models, the RCV

points down to theground and can bereplaced easily. Thevehicle must be jackedup and blocked to pro-vide proper accessspace. In fact, in most cases the compressordoes not even have tobe removed.

Once you locate the valve, simplyremove the snap ring and pull the valveout. Insert the new valve and re-instal

the snap ring. Pull a vacuum and chargeto specs. That’s all there is to it.

  As far as the VW Golf, Jetta, Passaand a few others, more work is requiredto replace the RCV than on the GM models. Yet, it is still fairly easy and certainlyworth giving it a try. The RCV is INSIDEthe compressor. To get to it, you have toremove the rear compressor cove(again, no need to remove the compres-sor).

Remove the rear cover carefully. It’s

held in place by 7 bolts. Avoid damagingthe gaskets between the cover and thecompressor’s body (Photo 2A). Once thecover is off, the reed valve plate wilcome off. Installed in it, you’ll see theRCV (Photos 3, 4, and 5).

The valve is held in place by a 7/16”nut in the opposite side. Remove the nut(Photo 6), remove the valve, replace itand re-install the gear plate and coverPull a vacuum and charge to specs.

In both cases, replenish the system

Don’t change out a compressor ifall that’s needed is a RefrigerantControl Valve. Here’s how it’sdone.

Photo 2. An actualRCV for both the V5and V7

Photo 1. Locating the RCVon a GM V5 compressor

Decreased Cooling In GM And VWCars And Trucks Could Mean A Faulty Refrigerant Control Valve,Not A Failed Compressor

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Revenue From Labor Instead of Parts Sales

with 3-4 ounces of specified PAG or min-eral oil.

Now, remember from above whenwe told you that with some modificationsyou could get by without the valve (if bychance you can’t get them)?

Doing it will essentially convert yourvariable displacement compressor into afixed displacement compressor. Simplystated, either eliminating or blocking thevalve does it. You will, however, need toinstall a low-pressure switch or a conven-tional thermostat to keep the evaporatorfrom freezing.

The procedure in both cases is simple.

For the V5/V7 compressor, you haveto remove the RCV’s as shown. (Photos7, 8, & 9). Now, with a tailored top (it can be aluminum or steel, or even alu-

minum brazing), seal the orifice. Makesure the top is secured by pressing it intothe receptacle. (Photos 10 & 11)

Re-install the valve in the compressoand secure it with the snap ring.

This cancels the variable stroke designfeature of the compressor; it is now afixed stroke. Therefore, a compressorcutoff means must be provided to avoidevaporator freezing. It can either be athermostat or a low pressure cyclingswitch that’s wired into the vehicle’selectrical system.

For the SD7V16 Volkswagen compres-

continued from page 1

Photo 9. Removing theRCV from a V5

Photo 10. The RCVsensor on a V5

Photo 11. AV5 RCVwith thesensorremoved

Photo 12. A SD7V16with the RCV removed

Photo 6. RCVand nut

Photo 5. Closeup of RCV installedin compressor

Photo 7. V5 RCV snap ring

Photo 8. PullingRCV on a V5

Photo 2A. SD7V16 gasket topview

Photo 3 Mounted compressorwithout rear cover

Right: Photo 4 Rear compressorcover internal view

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 Air Conditioning Service—The Problem Is Not Always What You Think It Might Be

CPM · April/June 2005 · 3

sor, the RCV is simply replaced by a 7/16”X 1” bolt and nut as shown (picture 12).

In the case of the SD7V16, don’t besurprised by a noticeable suction pres-sure drop below 15 at once. Given thecompressor’s design, it is normal.

Like in the GM compressors, a clutchcutoff method must be provided to avoidevaporator freezing. $$$

Photo 13. SD7V16RCV eliminated