dberladyn

Your theory makes sense. However, that helps no one in Arizona during the Summer. To me it makes sense to open everything and allow the whole system to breathe freely. You have to account to for all factors designing this stuff. Unless one of us proves our stance to the other I'll stick with my interpretation of the schematic.

cody laws

The actuator for the heat isn't moving. The van I stole it off made the door stay open that the only reason I have heat.I believe there is going to be another actuator on driverside. All my vacuums are plugged in where they are supposed to be.I'm guessing my switch is missed up or driverside actuator. I can make the defrost cold by moving the temperature ****. But nothing blending.

dberladyn

The Hot/Cold **** is an Electrical Potentiometer, not a Vacuum Switch.. I have one that works sitting right in front of me. It is less than three months old. I pulled it out of my new truck three years ago and installed a different one with the Defrost Button for the mirrors. I do not believe that there is a drivers side and a passengers side valve for any of the HVAC System. It is just the one valve per the schematic and the rest is duct work. We have nothing 'fancy' in these trucks.

Next Question

Do you let the truck get warmed up properly before assessing that the HVAC heat does not work? I am asking because if you look at the schematic there is a control that comes from elsewhere. No heat is given until the coolant system is warm enough to provide it. This is the Temp Control Valve on the LEFT of the Schematic for the Water Valve. For heat related functions there is more than just the Temperature Valve Actuator Motor on the RIGHT.

Maybe the problem is ELECTRICAL ?

mountainmanjoe

I think it's because holding a valve/door open or shut with electricity, for example with a solenoid, would require constant power usage. Not only does that consume energy, but it means that the part will eventually burn out.

In a manner of speaking, vacuum is "free", and once your moving part is open or shut, it will hold there tightly without further expenditures. It's also simple, reliable, and longer lasting.

mountainmanjoe

I have looked really hard, and found no external water valves on my 2013 van. I think there are no more heater valves.

Due to emissions laws, these newer cooling system designs have a bypass valve inside the water pump. The heater circuit is parallel with this valve. When cold, the bypass valve is open which means pressure at the heater input and output are equal. In, addition the return line is smaller diameter. The results is that the coolant takes the path of least resistance: through the bypass. Once coolant approaches operating temperature the bypass valve starts to close. This creates high pressure on one side of the heater circuit, and low pressure at the other, so coolant starts to flow to the heater core(s). This is done to get the engine up to operating temperature quicker.

I'm not sure which year GM updated this on the vans, but you can identify these newer systems by the thermostats mounted to the water pump intake (radiator output side). They used to sit at the top of the engine (radiator intake side).



Cold Engine








Hot Engine






The Vortec/SBC water pump

dberladyn

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