A/C - Sight Glass Elimination to Prevent Misdiagnosis

Bulletin No.: 002/94
Issued: 4/15/94
Revised:

Category
U

Applicable Model/s
See Below

Subject:
ELIMINATION OF SIGHT GLASS

APPLICABLE MODELS

Year / Model

1994 MX-3

1994 MX-5

1994 626/MX-6

1994 MPV (single A/C)

1995 PROTEGE

DESCRIPTION
The sight glass will be eliminated from R134a A/C systems on the above mentioned models. This is to prevent misdiagnosis of the system if the sight glass is used to determine the system's refrigerant level. At high temperatures, R134a refrigerant separates from the PAG oil creating a cloudy appearance. This cloudy appearance can be mistaken for air bubbles caused by low levels of refrigerant. Accidently over charging the system could result and damage to the system or poor cooling performance may occur.

ACTION
Do not use the sight glass for inspection of the refrigerant level.
A copy of the correct procedures for R134a refrigerant level inspection is included.

REFRIGERANT INSPECTION PROCEDURES FOR VEHICLES CONTAINING R134a REFRIGERANT

WARNING -
IF THE VEHICLE HAS BEEN SERVICED AND OZ-12 (AN AFTERMARKET REFRIGERANT) USED TO CHARGE THE A/C SYSTEM, DO NOT ATTEMPT TO DIAGNOSE THIS VEHICLE FOR SYSTEM LEAKS USING A CONVENTIONAL LEAK DETECTOR. THESE DETECTORS USE AN ELECTRONICALLY GENERATED ARC WHICH CAN IGNITE OZ-12. IF YOU FIND OR SUSPECT THIS REFRIGERANT WAS USED, CONTACT THE LOCAL FIRE MARSHAL OR EPA OFFICE FOR HANDLING INSTRUCTIONS.

DO NOT USE THE SIGHT GLASS TO DETERMINE CONDITION OF R134a REFRIGERANT

A - CHECKING REFRIGERANT AMOUNT
1. Install a manifold gauge.
2. Check the manifold pressure reading with the engine stopped. Pressure should be 493 - 788 kPa (5-8 kgf/sq.cm, 72 - 114 PSI) for both high and low pressure sides when the A/C systems high and low sides have equalized. If the pressure reading is:
a) zero (0), proceed to Section A.
b) lower than specified, proceed to Section B.
c) within specification but insufficient cooling is experienced, proceed to Section C.
d) within specifications and the cooling performance is not a problem, the system is OK.

SECTION A - CHECK FOR GAS LEAK AS FOLLOWS
1. Visually inspect A/C system (look for components covered with refrigerant oil). Suspect a leak if oil is found.
2. Discharge refrigerant from A/C system.
3. Evacuate the system to 750 mmhg or higher.
4. Stop evacuation and wait five (5) minutes.
a) If vacuum holds, system has no leaks. Recharge system according to the amount specified on the charge label.
b) If the vacuum does not hold, proceed to step 5.
5. Charge the system with one (1) pound of refrigerant and check for leakage using a R134a leak detector.
6. Repair or replace as necessary. Repeat steps 2-4 for confirmation. If the confirmation is OK, recharge the system according to the specifications on the charge label.

SECTION B - IF PRESSURE READING IS LOWER THAN SPECIFIED, CHECK FOR LEAKS AS FOLLOWS
1. Visually inspect A/C system (look for components covered with refrigerant oil). Suspect a leak if oil is found.
2. Discharge refrigerant from A/C system.
3. Evacuate the system to 750 mmhg or higher.
4. Charge the system with one (1) pound of refrigerant and check for leakage using a R134a leak detector.
5. Repair or replace as necessary. Repeat steps 2-4 for confirmation. If the confirmation is OK, recharge the system according to the specifications on the charge label. 6.

SECTION C - PRESSURE READING WITHIN SPECIFICATION BUT INSUFFICIENT COOLING EXPERIENCED
1. Start engine and turn the A/C on, set fan to "max" speed, recycle mode. Increase engine speed to 2,000 RPM
2. Check the compressor for short cycling. If this occurs, note the low side pressure when clutch disengages.
a) If the pressure is 24 psi or lower, evacuate and recharge the system according to the amount specified on the charge label.
b) If the pressure is 30 psi or higher, check the thermo sensor according to the instructions in the workshop manual or BETM.

NOTE:
Under the Clean Air Act, refrigerant added for leak detection must be recovered and not vented. After the system problem has been identified, and the necessary repair completed, the system should again be thoroughly leak tested.

B - CHECKING REFRIGERANT PRESSURE
Refer to the BETM