2005 GMC Z71 Heating and Cooling problem

[brentgrantham]

Hey Guys.

 

I just bought this 2005 GMC Z71 and the heating and AC is not working properly. Has the dual thermostat control.

 

When the truck is warmed up coolant wise...

 

I can have the temp set on 90deg for both sides and it blow cold as ice. Then in 10 min of driving it could change to hot. The in 2 min it could change back, then in 2 min it could go to luke warm, etc. etc..?

 

I took it into the service department and he diagnosed the driver side actuator. Which doesn't make since when both side are doing pretty much the same thing.

 

Any suggestions???? PLEASE!!!

[scott28641]

Had same problem, drivers side actuator fixed it

[brentgrantham]

Thanks for the comment. Kind of an odd fix though... Right?

[scott28641]

Just make sure it's the 2 left vents. I have heard this complaint a lot at the dealership and in most cases it was either the LH or RH actuator. Make sure your coolant is all the way full. One more thing to check is make sure your heater core is flowing properly

[brentgrantham]

Thanks for all the comments. Whats the best way to check the heater core?

The truck ran hot yesterday and we could smell antifreeze.

[scott28641]

Feel both hoses going into your firewall, see if both are hot. Back flush you heater core if not. I blow coolant through with an air hose, it works for me. If it is running hot, check your coolant level, fans. The thermostat could also be stuck. A water pump and thermostat are very easy and cheap to replace vs. cracked head or block