Check the ignition E fuse (10A).
Are you cetain that the system has enough refrigerant in it?
There is also a low pressure switch on the line going into the evaporator. If it is faulty or senses low presssure the compressor will not be allowed to come on.
That little snowflake that has the cross in it to show when the A/C has been turned off. The replacement control heads snowflake does not have the cross in it and actually needs to be lit up now to show that the A/C has been turned on. I think the only year for the snowflake with the red slash was 2003.
Testing compressor clutch/wiring:
Key on engine off, Jump the A/C clutch relay from pin 30 to pin 87, Compressor clutch should "click". If no click, check for power at the green wire at the compressor. Check the black wire for ground.
Testing low pressure switch:
With the truck running, A/C turned on. Check the dark blue wire at the low pressure switch for five volts with the switch Disconnected. Check for ground on the black wire. With the switch plugged in both wires should show ground. If the blue wire still shows five volts. Your low on Freon or the low pressure switch is bad.
Testing high pressure switch
1. With key on, disconnect the A/C pressure sensor and check for five volts on the gray wire. Check for ground on the black wire.
2. If missing either circuit, check a few inches back from the connector and see if voltage or ground is present there.
3. If the above checks are okay, then plug the sensor back in and probe the red/black wire of the sensor and see what voltage is coming from the sensor. With static A/C pressure voltage should be 0.8-1.0 volts.
On 2003 model year vehicles, a snowflake with a slash through it is shown on the display when the A/C has been turned off (by a press of the A/C button). The A/C can be turned on by pressing the "auto" button or pressing the A/C button again. This will remove the indicator from the display.
Owners of 2003's may comment about poor A/C performance after they have pressed the A/C button and see what appears to be the snowflake illuminated on the display. What has actually happened, though, is that they have disabled the operation of the A/C compressor and the snowflake symbol, upon closer inspection, has a slash through it.
Here is the AC and compression wiring diagrams so you can see how the system works with a guide to help you test the circuits.
Check out the diagrams (Below). Please let us know what you find. We are interested to see what it is.
Images (Click to enlarge)
Tuesday, July 23rd, 2013 AT 9:59 AM