Replaced thermostat now having AC problems

[KLPEARS1]

Hi all,

I just replaced the thermostat on my 06 Envoy because of the code saying it was below normal operating temp. I went through all the steps of changing the thermostat, removing alternator and disconnecting the battery. Now the new thermostat is installed along with alternator. I reconnect the battery only to find I now need to replace the mode actuator. (I now have new mode actuator and every thing works fine.) Now for my new problem, I am taking test drive to make sure everything is operating and letting the new thermostat cycle. All of a sudden my engine temp gauge drops (to the cool side) and the ac quits working. I pull over and stop the engine. I check to make sure that I still have pressure on the radiator lines and full of coolant, and that I am not overheating. everything is fine I start the engine, temp gauge is back to normal . I get home check all HVAC fuses and all is fine so I reset computer and ac works again. what could have caused my ac to quit.

Thanks.

 

[meerschm]

I would make sure the terminal is snug on the battery, and that the generator connector is making good contact.

also make sure you did not pinch the temp sender somehow in the process.

are you sure the coolant is full and no air bubbles in the system?

 

[gmcman]

Make sure the temp sensor harness is firmly connected. Generally the fan clutch will fully engage when there is a disconnect but I agree it sounds like a temp sensor lead may possibly be an issue.

 

[KLPEARS1]

I will have to check the temp sensor tomorrow when I have some day light. the battery terminals are tight so are the connections to the alternator. When the temp gauge dropped the fan was engaged. when I replaced the coolant I replaced about two gallons of 50/50 mix dexcool. As soon as I am able to check temp sensor I will let you all know what I find.

 

[KLPEARS1]

Make sure the temp sensor harness is firmly connected. Generally the fan clutch will fully engage when there is a disconnect but I agree it sounds like a temp sensor lead may possibly be an issue.

The temp sensor is not located by the thermostat. Where else would it be located? I know the temp sensor on my 05 TB was right by the thermostat.

 

[gmcman]

Right alongside. Connection is up by the FPR.

 

[gmcman]

Now I see you have an 06, not sure if it's the same...thought it was.

 

[meerschm]

A marine on the site found his on the other side of the block closer to the firewall.

http://gmtnation.com/f24/4-2l-i6-head-removal-engine-restoration-4425/index14.html

see post 395 in this thread, (save the whole read for a quiet evening)

 

[KLPEARS1]

A marine on the site found his on the other side of the block closer to the firewall.

http://gmtnation.com/f24/4-2l-i6-head-removal-engine-restoration-4425/index14.html

see post 395 in this thread, (save the whole read for a quiet evening)

I will check that out when I get home. My Haynes Manual didn't say anything about a secondary location.

 

[KLPEARS1]

I will check when I get home. My service manual did not say anything about a second location.

 

[KLPEARS1]

I checked the temp sensor the connection is good, also got a friend of a friend to check the Envoy with a scan tool. He said every thing is fine. Since I started this post I have put over 200 miles on the Envoy driving in Memphis traffic and no other problems. Maybe there was some trapped air in the cooling system.

 

[meerschm]

the motivation to suggest you check the sensor wiring was based on the assumption it was close to the thermostat, which you changed. since yours is on the other side, it is unlikely that it would have been even touched.

glad you are doing well hope it stays that way.

 

[KLPEARS1]

the motivation to suggest you check the sensor wiring was based on the assumption it was close to the thermostat, which you changed. since yours is on the other side, it is unlikely that it would have been even touched.

glad you are doing well hope it stays that way.

I hope it stays that way too. I hope I can get a few more years out of it. Thanks for all the help guys. I will make sure I let my GMT driving friends know about GMTnation.com.

Thanks a million

 

[MAY03LT]

All of a sudden my engine temp gauge drops (to the cool side) and the ac quits working.

Well I'm a little late to the party on this but I did skim the service info to see if there is any relation to low engine temp and a/c operation. I didn't find anything other then the a/c (compressor clutch) will be turned off if the engine temp gets too high. I think that if it happens again, leave the a/c on and engine running and pop the hood and see if the a/c compressor clutch is engaged. I suspect that I wouldn't be. At least this will give us something to go on.

But hopefully it learned its lesson and will not act up again.