Heater not working on my 2000 Blazer 4.3L. Where should I start?

Yes but it doesn't seem to change completely from vent to defroster or floor vents. Also, it seems the temp switch is moving too freely, maybe a bad cable??? Think I'll try backflushing first. I saw comments about a temp flow switch located in one of the heater core lines....does this have to be removed first??? Yes but it doesn't seem to change completely from vent to defroster or floor vents. Also, it seems the temp switch is moving too freely, maybe a bad cable??? Think I'll try backflushing first. I saw comments about a temp flow switch located in one of the heater core lines....does this have to be removed first???

Thanks Jeff Thanks Jeff

I take it by you mentioning temp cable you have manual temp control and not automatic ? Big difference in the two ! I take it by you mentioning temp cable you have manual temp control and not automatic ? Big difference in the two !

What does the coolant look like ? What color ? Does it have dex-cool orange or has it been changed to green . Some times dex cool clog's up the coolant passages if mixed with air in the system or green coolant ! What does the coolant look like ? What color ? Does it have dex-cool orange or has it been changed to green . Some times dex cool clog's up the coolant passages if mixed with air in the system or green coolant !

Your system doesn't have a cable , it has a air temperature actuator ,electric motor ! Pull out the glove box The air temperature actuator is located on the top right hand side of the heater/vent module.
Disconnect the electrical connector (2).
Also has vacuum controls for mode door operation . vent, floor , defrost !
Remove the air temperature actuator retaining screws.
Remove the air temperature actuator from the heater/vent module. Your system doesn't have a cable , it has a air temperature actuator ,electric motor ! Pull out the glove box The air temperature actuator is located on the top right hand side of the heater/vent module. Disconnect the electrical connector (2). Also has vacuum controls for mode door operation . vent, floor , defrost ! Remove the air temperature actuator retaining screws. Remove the air temperature actuator from the heater/vent module.

Connect the electrical connector (2).
Install the instrument panel carrier. Refer to Instrument Panel Carrier Replacement in Instrument Panel, Gauges, and Console.
Perform the following procedure in order to initialize the air temperature actuator on vehicles equipped with automatic climate control (C68).
5.1. Turn the ignition switch to the OFF position.

5.2. Remove the RDO BATT fuse for 10 seconds.

5.3. Reinstall the RDO BATT fuse.

5.4. Turn the ignition switch to the ON position.

5.5. Ensure that the air temperature actuator cycles through the hot and cold range.

Perform a heater output temperature check. Refer to Heater Output Temperature Check . Connect the electrical connector (2). Install the instrument panel carrier. Refer to Instrument Panel Carrier Replacement in Instrument Panel, Gauges, and Console. Perform the following procedure in order to initialize the air temperature actuator on vehicles equipped with automatic climate control (C68). 5.1. Turn the ignition switch to the OFF position. 5.2. Remove the RDO BATT fuse for 10 seconds. 5.3. Reinstall the RDO BATT fuse. 5.4. Turn the ignition switch to the ON position. 5.5. Ensure that the air temperature actuator cycles through the hot and cold range. Perform a heater output temperature check. Refer to Heater Output Temperature Check .

The mode door actuator is located on the top left side of the heater/vent module.

Remove the knee bolster. Refer to Knee Bolster Replacement in Instrument Panel, Gauges, and Console. Remove the right side driver knee bolster bracket (2) from the steering column bracket (1) and the intermediate bracket (3). The mode door actuator is located on the top left side of the heater/vent module. Remove the knee bolster. Refer to Knee Bolster Replacement in Instrument Panel, Gauges, and Console. Remove the right side driver knee bolster bracket (2) from the steering column bracket (1) and the intermediate bracket (3).

Disconnect the vacuum connectors (1) from the mode actuator (5).
Remove the actuator rod retaining clip (4).
Remove the actuator rod (2) from the mode door lever (3). Disconnect the vacuum connectors (1) from the mode actuator (5). Remove the actuator rod retaining clip (4). Remove the actuator rod (2) from the mode door lever (3).

Thanks Jeff. I'll try these.....or show it to someone who might have a better understanding of the components. I don't suppose you have a diagram to share that would correspond to your numbers. My son is a motorcycle mechanic and he is going to help me. Thanks Jeff. I'll try these.....or show it to someone who might have a better understanding of the components. I don't suppose you have a diagram to share that would correspond to your numbers. My son is a motorcycle mechanic and he is going to help me.

Coolant should be ok as I had it flushed last year....but that's about the time my trouble started....hmmmmm. Coolant should be ok as I had it flushed last year....but that's about the time my trouble started....hmmmmm.