Hot to Cold AC
Thread Starter
Heel & Toe
Joined: Apr 2010
Posts: 15
Likes: 0
From: Auburn GA
Hot to Cold AC
AC started cycling from hot to cold. Stared all of a sudden. Cycles about every 20 seconds. Does the same thing on auto or any level you choose. Also several days before the auto fan quit working. Can adjust manuely.
Thread Starter
Heel & Toe
Joined: Apr 2010
Posts: 15
Likes: 0
From: Auburn GA
Mine is electronic. The clutch is engaged, and the a/c works just the air coming out of the vents goes from hot to cold. It's like the mix door is going from hot to cold. What controls that and where is it?
Burning Brakes
Joined: Apr 2009
Posts: 877
Likes: 0
From: Broken Arrow Oklahoma
A/C heater programmer and it's located under the dash on the drivers side. It's hard to see and harder to get to. you need to remove the knee bolster.
Check the mix door. it has a small motor and a rod with a plastic keeper that breaks pretty easy.
also check the tree vac. valve (plastic part) in the engine compartment.
Check the mix door. it has a small motor and a rod with a plastic keeper that breaks pretty easy.
also check the tree vac. valve (plastic part) in the engine compartment.
Instructor
Joined: Aug 2010
Posts: 230
Likes: 0
From: Vermilion Ohio
RLG, Thanks, mine has c68 then...I just got it recently and noticed the air was not working. I turned on the a/c (I think) and the compresser was'nt running, I jumped the low pressure plug and it still didnt go. checked all the fuses and were ok. I am going to check the plug at the clutch with a test light today.
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Instructor
Joined: Feb 2006
Posts: 165
Likes: 1
From: rowlett tx
I have the same problem. When I put it on max a/c (60) it works fine, but when the temp is turned up a little, it will go from hot to cold just like you are describing. It's like when the blend door needs to adjust just a little to maintain temp, it goes all the way. I have absolutely no problems with the heater in the same way though...works great 
7th Gear
Joined: Feb 2008
Posts: 7
Likes: 0
From: Blacklick Ohio
Me too
Exact same problem in my 96 lt4. Hot to cold in a cycle. plenty of pressure in the system. Feels like the blend door is just flapping, but in rhythm almost. Can't figure out where to start. Also Cruise control doesn't work, so maybe a vacuum problem???
