Tech Tip: Prescription for RX-7 A/C Repair

Tech Tip: Prescription for RX-7 A/C Repair

One summer afternoon, he dropped the car off for its 60,000-mile service and mentioned the air conditioning had stopped working. Also, air was only blowing out of the defroster ducts. After a "quick" test drive, I brought the car in to check out the problem.

Dr. Stewart’s "third generation" RX-7 is probably one of the most unique vehicles that I ever had the pleasure to work on. The car was an amalgamation of elegance, race-proven functionality and tastefully executed amenities. The seats, for instance, were very comfortable and covered in plush leather, but equipped with side bolsters and a five-point seat belt harnesses to keep the good doctor secure during a spirited romp through twisty turns or down the quarter mile at the local drag strip.

The dashboard housed a tachometer and speedometer that were both conveniently angled toward the driver for exceptional visibility. The tachometer boasted red line of 7,500 rpm and the speedometer indicated what I thought was an optimistic 180 mph. But according to "Turbo Doc," his 255 horsepower, Twin-Turbo rotary engine had occasionally boosted the speedometer needle "just a little past its designated stop." I had to take his word for it.

Although this car obviously had the racecar-like credentials, it still possessed most of the convenience features of a luxury car. It was equipped with electric windows, door locks, CD player and, of course, factory A/C.

Every 3,000 miles, Dr. Stewart brought his RX-7 to the shop for scheduled maintenance. He usually never had any problems to report, and over the years, the car had proven to be quite reliable – despite its hybrid heritage. But unfortunately, no car is ever trouble-free.

One summer afternoon, he dropped the car off for its 60,000-mile service and mentioned the air conditioning had stopped working. Also, air was only blowing out of the defroster ducts. After a "quick" test drive, I brought the car in to check out the problem.

Not wanting to waste a lot of time going down the wrong diagnostic path, I searched my trusty ALLDATA automotive information system for some help. I quickly found a factory technical service bulletin, which described the problem exactly. Here are the procedures it prescribed:

Description
Any 1993 – 95 RX-7, with a vehicle identification number of JM1FD333*S0400026 and lower may exhibit either of the following conditions when the air conditioning system is operated:
• No compressor engagement when A/C is switched on; or
• Air flow mode switch fixed in defrost position

These conditions may be caused by insufficient contact at the hazard switch connector. Changes in the production process have eliminated this problem in subsequent vehicles.

NOTE: The hazard switch harness also contains the A/C control connector. This improper connection does not affect the hazard switch operation.

Repair
1. Verify the complaint.
2. Remove the control panel and the heater control unit (Refer to Fig. 1).
3. Check the hazard warning switch terminals. Refer to Terminal Connection Examples for problem examples.
4. If the female terminals are damaged (expanded), remove the switch from the A/C control unit and replace it with a new part.
5. If the terminals are normal, re-assemble and test.
CAUTION: Avoid damage to pins by inserting the connectors straight. Refer to Terminal Connection Examples.

Terminal Connection Examples

Connectors
1. Hold the housings when connecting and disconnecting the connectors.
2. To avoid connector pin damage, align the connector and housing at the appropriate angle.
3. Slightly wiggle the connector right and left then slowly insert it straight into the assembly (Refer to Fig. 2 and 3).
4. Avoid misalignment or forcing the connection.

Harnesses
1. Do not stretch harnesses to connect connectors.
2. Route harnesses to provide slack in harness and no stress on connector (Refer to Fig 4).

As luck would have it, the source of the problem was just what the bulletin had described. The hazard warning switch terminals were damaged, so I removed the switch from the A/C control unit and replaced it with a new part. With everything reassembled, the A/C system worked flawlessly.

When Dr. Stewart returned to pick up his car, he was surprised how quickly we repaired the problem. He remarked, "You guys are amazing. If only I could always diagnose medical problems this quickly and accurately. Sometimes it takes a couple of visits to figure out what’s wrong with a patient." He added, "But then again, why do you think they call it ‘practicing’ medicine?" With that said, he paid his bill and mentioned that he couldn’t wait to go out to the drag strip. After he left, I called the tire shop down the street for a price on a set of new tires … being prepared is one of my prescriptions for success.

Written by ALLDATA Technical Editor, Rich Diegle. Rich is an Advanced Engine Performance Certified and ASE Master Technician with an Associate of Arts degree in automotive technology and 22 years of dealership and independent shop experience.

Courtesy of ALLDATA.

For additional information, visit www.alldata.com.

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