I can't figure it out, I can't get heat even when my temp gauge reads 200-220 degrees. It started a week ago, it worked fine but all of a sudden it doesn't work. I got the SES light and found out it shoots a 32 and 36 but dont know if that would effect the heat since the codes have to do with EGR and burn off sensor issues. I tried the blower on high, I would move the temp slide to the blue and then move back to red, it would get hot for a few seconds and then back to cold even when the car has been driven and totally warmed up...I could use help!!!

 

There's a vacuum line that adjusts the flap under the dash to make the air from the heater work. If that vacuum line is broken, it wont move the flap. Sorry I dont know where its at and cannot be more help, but thats my idea of whats wrong.

 

Update - got up this morning to get gas, after warming up I turned the lever to defrost and presto!!, got heat from the defrost. I moved the lever to vent and heat..still blowing cold air. I assume it must be a vacuum issue, I will leave alone for now..heat from defrost is better than nothing!!

 

Remove the climate control from the center console. Check the vacuum lines at the switch. Make sure that they're all connected and inspect for cracks. If those appear to be okay, you'll need to next check to make sure that the cable has not come un-done from both ends. The defrost setting is kind of a default so, the next step will be to check the other vacuum diaphrams. Without a vacuum guage it'll be hit and miss but, maybe you'll get luck and find one disconnected or a bad or pinched vacuum line.

Before you start the dash disassembly, I'd suggest getting a print out from your GM parts dealer if you can or another source. That way you'll have an idea of where the vacuum diaphrams are located and which parts may need replacing.

Good luck

 

i had something similiar to this happen with mine. on the pass rear side of the plenum there is a vacuum line that controls the movewment of the air between the different vents. it is all the way near the firewall under the penum cover i believe. for me it is near the map sensor, but i have a 92. hopefully this will help

 

Air out the defrost is the default for the air doors.As everyone suggested check your vacuum lines both underdash,at climate controls and underhood.If you have a vacuum issue underhood could also be the cause of the EGR SES.

 

The switch itself is often a problem. Stick you ear to the pass side of the HVAC control and listen for a leak as you change settings. In the following pic, the part is question is the white piece which appears to have fingers (the vac harness slips over them):

https://www.thirdgen.org/forums/atta...duct010707.jpg

JamesC

 

There are two vacuum rotary valves in the climate control center. They both can wear out and let vacuum leak. One valve has two ports and controls the heater control valve in the engine bay that alows coolant to flow to the heater core. The other valve controls the doors to which vents the air blows trough. The temp slide is a cable operated door. When you slide it, it controls a cable that operates a door, it alows either cold air to enter or sends air past the heater core. The lever on the door is common to break. This slide also works the 2 port rotary valve that send vacuum to the heater control valve when the slide is slid to warm and hot.