Just thought I’d throw this one up here in case there’s a simple fix before send it to the shop. My 2016 KW T880 is constantly putting hot air though the vent. Even when I have switch on cold, and fan off, the cab gets too hot as there’s a steady flow of hot air coming though.
Anyone else ran into similar issue or any idea on the issue?
Thanks
Vents blowing hot air all the time
Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by kestrel1, Jan 24, 2021.
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Most likely the heater control valve has failed, see if the is a manual valve on the heater hose line that can be turned off will confirm it.
kestrel1 Thanks this. -
Possibly a blend door issue
kestrel1 and Rideandrepair Thank this. -
If your someplace still warm this time of the year. Nothing might be wrong. Their always seems to be some hot coolant flowing thru the heater core. Unless your truck has the manual shut off valves to cut all the coolant flow off you will get hot air at about 68F outside temp I usually find. It only a problem if you a/c is not working and you go south on the winter. That how freightliner is anyway.
It could be something like others already said if you don't have any control of heat and it's winter.kestrel1 Thanks this. -
On my Freightliner C120, I have an electronic water control valve, which shuts the the coolant off from flowing to the heater core when on cold. It is controlled by a cab thermostat, which in turn is controlled by the the temp control dial that has a registered. I don't know about newer KWs, but I bet the system is electronically controlled. In which case, it could be a one of 3 parts that failed, like mine. Mine failed in the thermostat, and it defaulted to heat all of the time.
kestrel1 and RocketScott Thank this. -
I meant to say resistor, not registered. Stupid autospell!
kestrel1 Thanks this. -
I drove a 2016 Kenworth T680 for awhile that had this same issue. Always blew hot air, even with the HVAC ‘off’. I got to driving around in winter, putting the windows down every few minutes to vent the cab.
The company shop didn’t fix it. I just remember them saying it didn’t throw any codes when hooking it up to diagnostics.kestrel1 Thanks this. -
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Did you press the defrost button, the one all the way to the left? Then it's functioning normally. Try to find a copy of the Owners Manual it's actually explained in there.
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