I have a 2000 Chevy 1500 Silverado when the ac is on it blows hot air but the ac lines are cold and it feels like heater is on inside truck.not sure what to start checking first
Find the temperature control motor, go back and forth with temp control, and see if it moves the door lever. If not, tapping on it may bring it back to life, or if it’s making noise and not moving it’s no good. If this fails follow the suggestions below.
The ECC modules requires two voltage sources in order to operate. Voltage is available at all times through the RADIO fuse and the GVAC 1 Fuse. Check both of these fuses before doing the calibration procedure below.
When the ignition switch is in the RUN position, voltage is available through the HVAC I fuse.
The Electronic Climate Control (ECC) could be locked up. Try this procedure below; this will recalibrate the system if there are no other problems.
Turn the ignition switch to the OFF position.
Remove the RADIO fuse for 10 seconds and then reinstall the fuse.
Place the ignition switch in the RUN position and wait 40 seconds for the ECC module to initialize.
An HVAC control module logic lock-up could be the cause of these conditions.
Important: Prior to replacing the HVAC control head, review Corporate Bulletin Number 01-01-39-007.
Replace the HVAC control module may be required to repair this problem according to service bulletin 04-01-39-007 Date: June 17, 2004.
If this doesn't work then you will need a scan tool to check for trouble codes related to the A/C system.
Check for plugs under the dash related to the A/C system making sure they are plugged in properly. There is a service bulletin that states that a six wire plug and an eight wire plug may be routed improperly. The proper routing of the wiring harness is above the air distributor duct with no tension on the terminals in the connector. The routing is improper if the wiring harness is below the air distributor duct with excessive tension on the terminals in the connector. The excessive tension may cause poor terminal contact, resulting in open circuits, in the connector. The wires may also pull the terminals out of the connector or pull out of the terminal itself.
Try these suggestions and get back to with your results. If you still have the problem we can diagnosis the problem further.