Even on the econo setting ( no AC comp. running) the drivers side air is warm where the pass. side is normal outside temp. This tells me the mix door for the drivers side is not shut. Or, I notice there are 2 solenoid type valves under the hood by the ECU. They appear to be in line with the coolant hose. Do these shut hot coolant flow off the the heater core/ cores? If so could the driver's side not be shutting off?

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1996 E300D
1996 E320 Wagon 4MATIC
2003 Jetta TDI- GLS, 5-spd
1997 Passat TDI
2002 F350 Crew cab 4x4 Powerstroke
Jacobsen HR 15' cut ZTR w/ 80 HP Perkins diesel
Hustler 6' front deck with 28HP Kubota diesel