Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSMERCURY1991TRACER BASE, 4D SEDAN, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 122 (A/C-HEATER SYSTEM - MANUAL)TESTINGA/C SYSTEM PERFORMANCE
1991 Mercury Tracer Base, 4D Sedan, Automatic
A/C System Performance
1991 Mercury Tracer Base, 4D Sedan, AutomaticSECTION A/C System Performance
WARNING: This page is about a different car, the 1994 Mercury Sable and 1994 Ford Taurus. However, it is still accessible from the selected car via links, so may be relevant.
- Park vehicle out of direct sunlight. Connect manifold gauge set. Start and run engine at 1500 RPM. Set A/C controls to MAX A/C (recirculated air) and maximum cold.
- Set blower/fan on high speed and close doors and windows. Insert thermometer in center vent. Operate system for 10 minutes to allow system to stabilize. Measure center vent output temperature. Center vent temperature will be 34-46°F (1.1-7.8°C) with ambient temperature of 60-90°F (15.6-32.2°C). See A/C SYSTEM PERFORMANCE SPECIFICATIONS table.
- At about 68°F (20°C) ambient temperature, high side pressures should be approximately 100-200 psi (7.0-14.1 kg/cm2 ). Low side pressures should be approximately 22-47 psi (1.5-3.3 kg/cm2 ).
- As low side pressure decreases, high pressure side should increase. When A/C clutch disengages, low side pressure will increase and high side pressure should decrease. See A/C SYSTEM HIGH SIDE PRESSURE SPECIFICATIONS table. Low side pressure remains constant throughout normal operating range.
A/C SYSTEM PERFORMANCE SPECIFICATIONS
| Ambient Temperature °F (°C) | Outlet Air Temperature °F (°C) |
|---|---|
| 59 (15) | 34-46 (1-8) |
| 68 (20) | 34-46 (1-8) |
| 77 (25) | 34-46 (1-8) |
| 86 (30) | 34-46 (1-8) |
| 95 (35) | 36-48 (2-9) |
A/C SYSTEM HIGH SIDE PRESSURE SPECIFICATIONS
| Ambient Temp. °F (°C) | psi (kg/cm2 ) |
|---|---|
| 59 (15) | 75-175 (5.3-12.3) |
| 68 (20) | 100-200 (7.0-14.1) |
| 77 (25) | 125-220 (8.79-15.5) |
| 86 (30) | 130-235 (9.1-16.5) |
| 95 (35) | 175-285 (12.3-20.0) |
RENDER: 1.0x
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.