1997 blazer climate control problems

[hotrodbuilder]

Have a blazer with auto climate control where i can set the temp in degrees. Having a problem where at 74 degrees it barely gives anything out but bump it up to 80 degrees and it blows desert hot air on demand. Any ideas on what to check would be greatly appreciated.

Thanks in advance

[aleekat]

Originally Posted by hotrodbuilder

Have a blazer with auto climate control where i can set the temp in degrees. Having a problem where at 74 degrees it barely gives anything out but bump it up to 80 degrees and it blows desert hot air on demand. Any ideas on what to check would be greatly appreciated.

Thanks in advance

The classic Blazer heater core partially plugged.

[tigerhwk]

Doesn't sound like a heater core,You'd get no heat
More likely a temp sensor or computor issue to go from cold to hot like that

[old_master]

Try cleaning the contacts in the temperature control dial with TV tuner cleaner. Probably have to remove the control head to get at the contacts.

[hotrodbuilder]

I think the vacuum plunger on the door isnt working right, if i manually move it back i can get a full blast of warm air (with fan on high not auto), should i start tracing the vacuum line back to the control head?

[old_master]

That would be a good place to start.

[hotrodbuilder]

Where does the vacuum line from the plunger that opens the door run to? I dont have any vacuum lines going to my control head.. what else controls the plunger movement? where should i head to next?

[old_master]

Vacuum is supplied by the engine, routed to the vacuum electrical solenoid which is mounted on the heater housing, behind the glove box.

[hotrodbuilder]

Found vacuum getting to my plunger and opening door correctly which tells me the vacuum control is working right and im getting enough vacuum however the door only opens when put on floor or defrost mode to allow heat into the cabin but when i put it on face mode the door closes.. install a new dash controller?

Thanks for all the help so far

[old_master]

You have checked the "simple" stuff, to acurately diagnose automatic climate control you need a body capable scan tool. Unfortunately, the GM dealer is probably your best bet now.

[aleekat]

Your posts have me confused. Your first posts suggests you get no heat below the 80 setting,(only cold air blowing) but heat above. Your next post suggests you get no air blowing.

Doesn't sound like a heater core,You'd get no heat
More likely a temp sensor or computor issue to go from cold to hot like that

I have an 98 with the auto/clim. Same symptoms, below 80, cold air. Above 80, will cook you out of the car. After searching this forum, suspected heater core "partially" clogged. Know issue, with rad caps, dexcool. Drained and flushed the sytem, and backflushed the heat core several times. Replace the cap and dexcool with green. Works like advertised. GM acutally has a TSB on this, they want $400 for a completed system acid flush with no guarantee it will fix the problem.