As the cooling season rapidly approaches, Subaru vehicles needing A/C service or maintenance will soon drive into your shop. Here are some Subaru specifics to help you service them.

It’s that time of year – when vehicle owners begin to feel the warmth of the springtime sunshine and realize their air conditioning systems need service or checkups to keep them cool during the torrid temps of summer. It’s also time for you to prepare for a parade of sweaty customers, frantic for cool air.

As Subaru vehicles arrive at your shop for other maintenance or repair, it’s time to inspect the A/C systems, too. You’ll want to consider the following information when servicing Subaru A/C.

Subaru Policy on Sealants and Dyes

Subaru strongly advises against the use of A/C system sealants and advises that the use of such products may affect any existing warranty coverage.

Likewise, Subaru does not recommend the use of dyes to detect leaks in A/C systems. Because dye can change the viscosity of the oil, it can therefore affect the performance of the system and compressor life.

Subaru recommends the use of electronic leak detection tools, such as the Kent-Moore J-39400-A Halogen Leak Detector. The tool is available from your Subaru N.E.W. Horizons Dealer or on the Subaru Tech Information System website at http://techinfo.subaru.com, where there’s a link to the Subaru Special Tool website at .

Electronic “sniffer” leak detectors can find even the smallest amount of refrigerant seeping from the A/C system, but take a little more time and patience to use than dye detection. Training and experience is required for using a detector. The sensor head must be moved slowly and in close proximity to all connections, hoses and components.

If a Subaru vehicle arrives at your shop with dye already added to the A/C system (which should be indicated by an underhood tag) from previous service, use of an ultraviolet light is one good way to look for a leak. Some leaks may not quickly and easily be detected by an electronic detector. Of course, the presence of dye may indicate there was a previous leak. Any records of the prior A/C service, or questioning the customer, may help in diagnosing and repairing any problem.

Basic Types of Subaru Compressors

Since the early 1990s, Subaru has used three basic types of compressors:

• Axial Piston: This type was used on the SVX and Legacy models until 1993. The SVX used an ECM-controlled variable displacement wobble-plate version. A ZEXEL swash plate design was used on Legacy models. These units have been known to knock if refrigerant pressure is too high.
• Rotary Vane: The vast majority of Subaru vehicles on the road today are equipped with rotary vane compressors. Some complaints of a “buzzing” noise have been reported. This may be caused by the trigger valve, which shifts pressure to the shaft side of the vanes at low speed.
• Scroll Type: In 2005, Subaru converted to scroll type compressors. To date, no major concerns have been reported.

While there are some unique variations, most of the rest of the line has remained consistent. For example: some of the earlier A/C units were hung on in the U.S. The 1988-1990 Leone and Loyale with factory-installed A/C units used a Hitachi compressor; those with units installed this side of the Pacific used a Wynn’s A/C kit (SOA329A115). The kit used a clutch-less compressor (SOA329A340).

Similarly, Justy models of the era were U.S.-mounted with a Wynn’s A/C kit. The kits for carbureted models (SOA329A110), or for MPI models (SOA329A112), used either a compressor with a clutch (SOA329Y202), or a clutch-less compressor (SOA329Y203).

Refrigerant Recovery

The purpose of evacuating the maximum amount of refrigerant when servicing an A/C system is to avoid overcharging when the service is complete. The best way to ensure you’ve removed the most refrigerant is to run the recycling equipment through two or three cycles, fifteen minutes apart.

Experts advise that you should not attempt to recover refrigerant in cold (ambient) temperatures. Lower temps inhibit the evacuation of the maximum amount of refrigerant. In order to recover the largest quantity of refrigerant possible, make sure the vehicle is at room temperature of 70 deg. F, or higher. Bring the vehicle into the shop and warm it up before recovering the refrigerant. While only 66% of refrigerant may be recovered at 50 deg. F with a single recovery procedure, up to 85% can be recovered at 70 deg. F, with two or three cycles.

Be sure to always use Genuine Subaru R-134a Refrigerant when servicing Subaru vehicles. You can rest assured it’s pure, clean and meets the standards for Subaru service and warranty.

Critical Compressor Oil

Here’s a subject that can’t be stressed enough: The correct compressor oil, in the correct amount, is critical to proper A/C operation and compressor life.

Always use the right type. While R-12 systems use mineral oil, R-134a systems require poly alkaline glycol (PAG) oil. Never mix the two. There are different viscosities of PAG, so make sure you’re using the right one for the system you are servicing. Don’t mix PAG oils of different viscosities. Check the label on the back of the compressor for the proper amount and viscosity of PAG for the compressor and system.

Use the correct amount. Under-lubricating jeopardizes the compressor, and too much oil will not only affect the performance of the system, but can also damage the compressor. You can quickly find the correct specifications on the Subaru Tech Information System website at http://techinfo.subaru.com.

Lastly, keep the oil clean and moisture-free. The entire A/C system can be damaged by adding dirty or contaminated oil. During a visit to a repair shop a few years ago, we were astonished to see a technician adding PAG from a dirty, grimy bottle that had no cap to keep out moisture, grease, dirt and contaminants. Asking the tech why he was using the filthy bottle evoked the response, “We buy the oil in gallon bottles, but that’s hard to handle, so I put some in this bottle, keep it on my work bench and add what I need to the system.” The tech and shop owner were just asking for problems. Always use clean oil from a clean bottle and keep the cap on to protect the contents.

Subaru A/C Service Bulletin

The following Subaru technical service bulletin contains an important tip that applied to the 2001-2002 Legacy VDC and Outback LL Bean models with H6 engine. Subaru encountered some inadequate cabin cooling problems on these vehicles. The compressor revolution sensors developed an open circuit, resulting in short-cycling. To rectify the problem, Subaru issued Service Bulletin 10-74-02. It includes diagnostic and service procedures, as well as the replacement revolution sensor part number (SOA73190AE000). This may still pop up on some vehicles that have never had this problem fixed:

Diagnostic Procedure:

1. Confirm the customer’s concern.
2. Disconnect the three-pole connector on top of the compressor.
3. Check the electrical continuity between (B) and (C) as shown in the diagram.
4. If no continuity exists, the circuit for the revolution sensor is open and the sensor should be replaced.
5. Standard resistance should read approximately 1.62KΩ at room temperature and approximately 2KΩ warmed up.

Repair Removal Procedure:

1. Conduct the following operation to return the compressor oil with the refrigerant to the compressor.
   • Increase the engine speed to 1,500 rpm.
   • Turn the climate control to ON.
   • Turn the temperature control switch to the lowest temperature setting.
   • Put the control in RECIRC position.
   • Turn the blower control switch to HIGH.
   • Run the vehicle in this manner at 1,500 rpm for ten minutes, then turn the ignition switch off.
2. Disconnect the GND (-) cable from the battery.
3. Recover the refrigerant.
4. Remove the compressor. Cover or plug the ends of the high and low side hoses to prevent system contamination.
5. Clean the area around the revolution sensor.
6. Disconnect the ground wire for the sensor, retaining the screw for reuse.
7. Remove the revolution sensor connector.
8. Remove the rear retaining clip (brown) from the connector and remove the black wire (leading to the compressor clutch) from the connector, using the appropriate electrical pin terminal tool.
9. Remove the rear retaining clip from the connector and remove the yellow and black terminal pins (leading to the revolution sensor) from the revolution sensor connector after noting their positions.
10. Remove the revolution sensor from the compressor taking care to not damage the sealing surface of the compressor.

Installation reverses the removal procedure noting the following precautions:

1. Thoroughly coat the replacement O-ring, supplied with the new revolution sensor kit (P/N 73190AE000), with compressor oil and carefully install the O-ring onto the sensor.
2. Confirm that the O-ring is fitted correctly and install the revolution sensor, tightening to 11.6 ft-lb. (3 Nm).
3. After reinserting the two terminal pins back into the revolution sensor connector and ensuring their engagement, replace the rear retaining clip (brown) into the back of the connector using the new one supplied with the kit.
4. Reinstall the connector to its bracket and ensure its engagement.
5. Connect the ground wire of the revolution sensor to its original position and tighten to 2.2 ft-lbs. (3 Nm).
6. Charge the system with the proper amount of refrigerant and perform a system performance test to confirm correct operation.

Retrofit Procedures

Since Subaru vehicles last such a long time, there are still many on the road operating on R-12 refrigerant.

Subaru issued R-12/R-134a retrofit procedures way back in 1996, including all part numbers. That document, Service Bulletin 10-68-96R, is still applicable. It was reissued on 08-15-98.

Subaru lists correct A/C specifications on the Subaru Tech Information System website at http://techinfo.subaru.com.

The website also offers the helpful Subaru Technicians Reference Booklet for Heating, Ventilation and Air Conditioning (HVAC), Module 603, item #MSA5P0137C.

You can obtain a copy of the handy and informative Subaru A/C Service Reference Booklet from your Subaru N.E.W. Horizons dealer, or by downloading it from the Subaru Tech Information System website.