Last post on Jan 29, 2013 at 3:06 PM
You are in the Chevrolet Blazer
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Chevrolet, Heating / Cooling, SUV
#36 of 154 Re: Chevy Blazer heater flapper [stang_girl87]
Mar 03, 2007 (11:04 pm)
I think I might be having a similar problem.
I have a 1999 Blazer, Trail Blazer pacakge with auto climate control.
The system will blow cold, then I'll hear something squeak in the dash and all of a sudden it blows hot. Every 10-15 iseconds t switches, hot to cold. The cycle repeats when the engine is running, regardless of what position the temperature selector is at.
Is that flapper box bad? Or could it be the control unit? Any advice?
#37 of 154 Re: Chevy Blazer heater flapper [delbiage]
Mar 04, 2007 (2:45 am)
The electric blend motor (witha plastic gear) is probably trashed and I would strongly suggest the dealer on this - many other shops do not understand these and will actually cost more to determine and change - its behind the glove box and cycles the door between the AC and heater core based on the temp selected.
Try rotating the knobs to see if the contacts are dirty and this may clean them and see if running at all cold or hot stops the cycling. I never use that auto fan position cause I hate it ramping up and down.
#38 of 154 Broken heater door in 2000 blazer 4wd.
Apr 14, 2007 (2:42 am)
#39 of 154 Broken heater door in 2000 blazer 4wd.
Apr 13, 2007 (6:02 pm)
If i can get the dash out and the heater air handler
exposed can i get to the door near the steering column to repair it without removing the the entire
heating unit. Any make do fixes that can be done without complete disassembly of the air handler??
I would welcome a manual wire. My disabled expert
says the vacum motor is working and he can see it
move but the door just springs back. The vacum motors behind the glove compartment are ok.
Obviously i am looking at big bucks that i cannot afford. Any help or suggestions appreciated.
#40 of 154 Re: Broken heater door in 2000 blazer 4wd. [olddoc]
Apr 14, 2007 (2:41 am)
That air box requires the dash be pulled to get completely out if the internal door is jamming - but have to ask is this an LT with auto climate control (temps on dials and auto positions)? If so there is an additional electric blend motor accessible thru the glove box atop the air box that often fails. If not also look under hood at the drivers side vac lines 5/32" that run to the reservior in the fender and the last T in the system is a plastic line to the heater controls - rotted rubber lines may be causing the door to open then flip back as vac drops due to pressure and default for door is defrost.
#41 of 154 2001 Blazer blowing cold air
Jan 17, 2007 (3:08 pm)
#42 of 154 2001 blazer blowing cold air
Jan 17, 2007 (9:11 am)
I've already replaced the thermostat, which made no difference.
The car blows cold air until the temperature gauge gets up around 260, then suddenly drops down below 200.
Would my next step be to flush the cooling system? I don't see why it would be running hot though.
#43 of 154 Re: 2001 blazer blowing cold air [kcwebmonkey]
Jan 17, 2007 (10:48 am)
Hope it wasn't going to 260 before you did the thermostat! How about a new Stant cap - appears that the old one is not holding pressure. Then could be a clogged radiator. Dex cool should be flushed and changed 3/36 and that GM 5/100 info was crap. Air in the system would be another reason for a temp buildup as steam was hitting the temp sender mounted on the drivers side head between the rear 2 plugs. Make sure the heater core flows and see if the 2 hoses entering the firewall are hot and squeeze and see if water flowing. Sometimes due to the high mounting of the heater core air gets trapped in it and you hear gurggling.
#44 of 154 Re: 2001 blazer blowing cold air [repairdog]
Jan 17, 2007 (3:08 pm)
it was staying right around 200 before this week, when i noticed the problem and replaced the thermostat. i'll go ahead and replace the radiator cap as well, and if that doesn't help then i'll look into flushing the radiator/cooling system.
Thanks for the help.
#45 of 154 1999 Chevy Blazer Floor Vent Issues
Jan 16, 2007 (3:27 pm)