PREPARATION FOR TESTING
- Attach Low and High side gauges.
- Start engine and allow it to warm up.
- Set system to COOL and blower to HIGH.
- Open car doors and hood.
- Run at fast idle for 2-3 minutes.
OPERATIONAL TEST GAUGE READINGS
| Application (2) | Low Side Gauge (Suct.) | High Side Gauge (Disc.) |
|---|
| Ford Motor Co. |
| 1980 (STV) (2) | 28-31 | 175-195 |
| 1980 (Accumulator Type) | 24-52 | 160-200 |
| 1981 (Accumulator Type) |
| Escort & Lynx | 20-45 | 130-230 |
| Other Models | 24-52 | 160-250 |
| 1982-83 (Accumulator Type) |
| Ford, Lincoln, Mark VI Mercury | 24-52 | 160-250 |
| Other Models | 20-45 | 130-230 |
| 1984-88 (Accumulator Type) |
| Ford, Mercury Town Car | 24-50 | 160-250 |
| Other Models | 16-45 | 130-230 |
| (1) Pressure readings given are for a system in good operating condition, at sea level and an ambient temperature of 80° F 27°C). (2) 1980 Granada, Monarch & Versailles with ATC: Low Side pressure 14-24; High Side pressure 145-175. |
| (1) | Pressure readings given are for a system in good operating condition, at sea level and an ambient temperature of 80° F 27°C). |
| (2) | 1980 Granada, Monarch & Versailles with ATC: Low Side pressure 14-24; High Side pressure 145-175. |
NORMAL SYSTEM OPERATING PRESSURES (PSI) (1)
Air Conditioning System Performance Check. Scheme 22
Scheme 22: Air Conditioning System Performance Check
Ambient Temperature/Pressure. Scheme 23
Scheme 23: Ambient Temperature/Pressure
Evaporator Temperature/Pressure. Scheme 24
Scheme 24: Evaporator Temperature/Pressure
| Low Side Gauge | High Side Gauge | Other Symptoms | Diagnosis |
|---|
| Normal | Normal | (1) No or few bubbles in sight glass. High side gauge may go high. Low side gauge does not fluctuate with compressor on/off cycle. | Some Air and Moisture in System. |
| Normal | Normal | Cools okay in morning but not during hot part of day. Tiny bubbles in sight glass | Excessive Moisture |
| Normal | Normal | Discharge air warm when low side gauge drops into vacuum. Thermostatic switch system only-compressor cycles off and on too rapidly. Cycling clutch systems only-Compressor doesn't turn on soon enough. | Defective Thermo- static Switch |
| Normal | Normal | Discharge air becomes warm as low side pressure rises. | Misadjusted Thermo- static Switch or Defective Pressure Sensing Switch |
| Low | Low | Bubbles in sight glass. Outlet air slightly cool. | Low R-12 Charge |
| Low | Low | Sight glass clear or oil- streaked. Outlet air very warm. | Excessively Low R-12 Charge |
| Low | Low | Outlet air slightly cool. Sweating or frost at at expansion valve. | Expansion Valve Stuck Closed. Screen Plugged or Sensing Bulb Malfunction. |
| Low | Low | Bubbles in sight glass. Outlet air slightly cool. | Low R-12 Charge |
| Low | Low | Sight glass clear or oil- streaked. Outlet air very warm. | Excessively Low R-12 Charge |
| Low | Low | Outlet air slightly cool. Sweating or frost at expansion valve. | Expansion Valve Stuck Closed. Screen Plugged or Sensing Bulb Malfunction. |
| Low | Low | Outlet air slightly cool. High side line cool to touch. Sweating or frost on high side. | Restriction on High Side |
| Low | High | Evaporator outlet pipe cold. Low side goes into vacuum when blower is disconnected. | STV Stuck Open |
| High | Low | Evaporator outlet pipe warm. Outlet air warm. | STV Stuck Open |
| High | Low | Noise from compressor. | Compressor Malfunction |
| High | High | Outlet air warm. Liquid line very hot. Bubbles in sight glass. | Condenser Malfunction or R-12 Overcharge. |
| High | High | Outlet air slightly cool. Bubbles in sight glass. | Large Amount of Air and Moisture in System. |
| High | High | Outlet air warm. Evaporator outlet | Expansion Valve Stuck Open |
| (1) If equipped with a low refrigerant charge protection system, compressor operation may have stopped. |
| (1) | If equipped with a low refrigerant charge protection system, compressor operation may have stopped. |
A/C DIAGNOSIS W/GAUGES FOR SYSTEMS W/INSUFFICIENT OR NO COOLING
