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same problem

I didn't thin the 2 were related but yes my coolant temp guage when it is not reading then the AC will not work so must be some sort of connection but where to look?
 

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Thermostat getting stuck open.....had this problem for awhile.
They changed out thermostat and has been good for 5 days so far.....
Was told that temp has to reach around 215 for ac to kick on.
They said it was only about 160.....I don't know about that but it seems ok now. I had purchased a maintenance contract when I bought my 2008 TB about 4 years ago and the thermostat was covered. If not, it would have been 440.00
Was told it is not easy to change out (this was the Chevy dealer) so...............
 

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they told you a

that's a load of crap that coolant temp has to reach 215, it might have been your thermostat sticking but when you get in and turn the key and your gauges cycle and your temp gauge stays at the bottom at 100 and don't move with in a minute or so then that is your AC problem nothing else, the signal causes the computer to not turn on the AC for some safety reason. this a a $26 fix just replace the Engine Temp Coolant sensor its a pain but its the fix
 

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Well I will try that if it happens again. I was told by Chevy service department (whom I don't trust)that it was the thermostat....and they just did it I am guessing to get paid and they probably didn't want to troubleshoot. It didn't cost me anything and it's new so I said go ahead hoping that was it. Need to find a good mechanic as these dealers piss me off.
I originally went to where I purchased my vehicle and waited 5 HOURS... the service manager comes to me and says " it looks like a LOT of things going on" WTF is that??
He says "bring it to a GM dealer"!! Going to the dealer is a nightmare!!!
I will change out the sensor if it shows again...thanks!
 

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well only change it out if your AC don't work and your temp gauge don't work, when the computer sees no rise in engine temp from the gauge it turns off the AC in the even that engine is overheating and the AC just puts more heat thur the condenser infront of the radiator. Only change out if Temp gauge is reading 100 or not moving at all
:hissy:
 

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OK I have the same problem, When temp guage does not work, the A/C will not work, After driving a while the guage will start working and the A/C at the same time. If I disconnect the battery and reconnect all works fine for a couple of trips. Has anyone found a real fix for this, The ect sensor is hid pretty well. I took a pic of what I think is the connector, will try to attch, Can anyone verify that is it? 2008 trailblazer LS, 4.2 engine
I have a 2008 trailblazer, was throwing the 128 code low coolant temp. Also my a/c used to work fine but when the low coolant issue started the a/c compressor wouldn't run until the temp gauge jumped up to maybe the middle after driving for awhile. I was going to replace the thermostat since it seems like it's sticking. Was also thinking the 2 things are related somehow?
 

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I am convinced now that the intermittent temp gauge working and the intermittent a/c working are directly related. This was the 3rd time now that when the a/c was out and the temp gauge jumped up to normal the the a/c immediately started running and cooling. Going to replace the thermostat just as a precaution and start there!
 

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I replaced the thermostat yesterday, not a real easy job. So far the A/C comes on every time and my temp gauge rides right at 210 like before the problem. I will update if the A/C fails again intermittently.
 

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I happen to have one in my shop.. let me say there were some good comments on this tread.. but what’s not be said enough is the customers statement.. they can unplug the battery, then reconnect immediately and all goes back to normal for awhile. That’s a huge clue that give us direction.. also, the customers state that it CAN happen even when u first start up in the morning. Temp zero out and a/c not working.... so it’s obviously not sticking thermostat.... I’ll post a video on my Utube channel in a couple day. “ Hayes mobile Auto Repair “. This is interesting. I’ll also post on here.. we gonna figure it out once and for all! 😀
 

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FWIW my 2008 TB has the same issue. As a quick fix before I dove into thermostat/sensor replacement, I left my code reader plugged in. If the temp went to zero and the AC quit while driving, I could reset all codes by hitting the enter key 5 times and the problem went away. It would come back, randomly, after 20 minutes or so and could always be reset by erasing the code.
The AC won't go on at all now, so it looks like
there's no choice, but to replace the thermostat and sensor.
 

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FWIW my 2008 TB has the same issue. As a quick fix before I dove into thermostat/sensor replacement, I left my code reader plugged in. If the temp went to zero and the AC quit while driving, I could reset all codes by hitting the enter key 5 times and the problem went away. It would come back, randomly, after 20 minutes or so and could always be reset by erasing the code.
The AC won't go on at all now, so it looks like
there's no choice, but to replace the thermostat and sensor.
Had same problem with 08 trailblazer. Thermostat fixed. Seems like if the temp doesn’t come up as it should the system will not let the a/c work
 
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