How To
Test The A/C Electrical Section:
Saab 900
With Time Delay Relay
USE
THIS TEST IF YOUR A/C COMPRESSOR WONT TURN ON*** TESTING
FUSES AND SWITCHES ***
- Make sure fuse #6 & #25 are in order.
- Go to the little black switch on the receiver drier filter and bridge the two electrical connections. If the compressor turns on = You are low on freon. This switch is what is called the LOW PRESSURE SWITCH. If your freon level becomes low it will open the control circuit thus through the relay will turn the compressor off. This is a safety function, the lubricant for the compressor circulates with the freon so if the freon gets low you don't want to starve the compressor of oil.
- Go to the switch in the upper radiator hose. It is called the COOLANT TEMP SWITCH. It has two wires. The function of this switch is to turn off the a/c compressor if the engine temp becomes too hot. Bridge the two wires, if the compressor turns on = the switch is bad OR the motor is overheating.
- The EVAPORATIVE TEMPERATURE SWITCH "ETS" The purpose of this switch is to keep the Evaporator from freezing up , forming ice and restricting the flow of cold air inside the car. In which case it would also make the compressor work very hard. To test = you should have a circuit through it for the compressor to turn on. Bridge its two wire connector and if the compressor turns on = you found the problem. I have had a lot of cases where I just moved the connectors and the system starts working and all was well. If you have warm air output during a long trip, Look at the evaporator and if you see ice in there. You need to replace the ETS.
*** TESTING AT
THE TIME DELAY RELAY ***
Make sure the 900 is
running and the a/c is turned on. Remove the relay in location H in
the fuse box and test at the connectors the relay plugs into. You can
reference the numbers of the connectors by looking at the bottom of
the relay. You will need a low impedance test light or a volt
meter.
- Test #30 = You should have battery voltage.
- Bridge #30 to #87B = The compressor should turn on. If not bridge the wires at the COOLANT TEMP SWITCH. If the compressor turns on = you have a bad switch. If the compressor still wont turn on check the wiring at the compressor and the 6 pole connector stuffed between the body and the evaporator housing. It may be a good time to use a jumper wire from the battery + straight to the compressor to make sure the clutch at the compressor is working. Some of the compressors have a temp switch that screws into the top that can cause a problem but I have never seen one go bad.
- Bridge #30 to #87 = The fans at the radiator should turn on.
- Check That #31 is a good ground. Test by attaching the connector at the end of the test light to battery + or #30 at the relay connector and touching the end of the probe to #31 = The test light should light up.
- Check that #86 has power. If not check and bridge the two wire connectors at the Low Pressure Switch and the ETS SWITCH. There is a connector at the fuse box "H29-3" Its black and if you have a problem here just grab the connector from under the dash and move it. I have seen cases in older cars from the rust zone with a weak connection in this area.
- Check #50 = You should only have power here when the starter is working.
- Check #15 = You should have power here anytime the ignition key is turned to the on position.
- #16 Is where a signal comes out of the relay and goes to the LH ECU. The relay is looking for a ground from the ECU to turn the compressor on. Make sure you use a special low impedance volt meter or test light here or you can damage the ECU.
- #TK When the relay receives a ground signal from the throttle switch at wide open throttle It shuts off the compressor. You should have no ground here unless the throttle is wide open.
- If you unplug the relay, you have to restart the car before it will energize as it has to see the +50 signal to start its timer function and turn on the compressor. Back To Climate Control Index