A/C issue

[zilla14]

I have a 00 Silverado 1500 Z71 Ext. cab. 258,000 miles 4.8 auto. I am only geting air blowing from defrost vents regardless or wht the a/c control is set on. Is this a damper issue?

[j cAT]

Originally Posted by zilla14

I have a 00 Silverado 1500 Z71 Ext. cab. 258,000 miles 4.8 auto. I am only getting air blowing from defrost vents regardless or with the a/c control is set on. Is this a damper issue?

the HVAC door controls maybe inop because the battery may need to be disconnected. this can happens some times. like a reset .. have vehicle off key in your pocket ac set to off ... remove battery put foot on brake [30 sec.] pedal , to drain any battery power. then reconnect and hope for the best.

[zilla14]

Tried reset, didn't work... Any other ideas? where is control servo located?

[j cAT]

Originally Posted by zilla14

Tried reset, didn't work... Any other ideas? where is control servo located?

what type HVAC do you have auto or manual ?

[zilla14]

not sure.... how can I tell?

[777stickman]

Originally Posted by zilla14

not sure.... how can I tell?

A manual head controller has dials and buttons. An auto controller has digital read-outs.

Is your '00 an Old Body Style (looks like a '98) or New Body Style (looks like an '01)?

On the OBS the Mode Door and motor are located just to the right of the throttle pedal on the left end of the heater plenum. There is also visible linkage at that point that many have had issues with coming disconnected relating to Vent, Floor & Defrost.

[zilla14]

it is manual control.. New body style.

[j cAT]

Originally Posted by zilla14

it is manual control.. New body style.

if none of the HVAC buttons work properly it is locked up in DEF mode then my guess is the HVAC module. this is located under the radio.

Now the dealership with this vehicle can pull body HVAC failure codes. this will confirm this if bad. also could be the mode door motor. normally this does not suddenly lock up in DEF MODE.. this is to the left of the control module.

I would try scrap yard first. swap out the module. just to be safe check all the fuses.

[zilla14]

I tried 2 other control modules with same result. it blows hot and cold air just fine just stuck in defrost mode...

[j cAT]

Originally Posted by zilla14

I tried 2 other control modules with same result. it blows hot and cold air just fine just stuck in defrost mode...

hot cold is the temp motor ... the door control is the one you have problems with. like I said that is to the left of the HVAC control module. 5 volts DC makes this steeper motor move check it out see if it is jammed. unscrew the motor assy and see if it moves when you change the air flow. see if with your finger you can move the duct lever.