Freightliner Columbia 120 AC Only works at idle. Nice and cool , blows hard. About 5 minutes into driving the air velocity becomes weak and does not change no matter what the blower control is set to.
Shop looked and said don't keep it on recirculation for very long because it will freeze. So we stopped using recirculation button and it still happens.
Any thoughts?
Freightliner Columbia 120 AC Only works at idle
Discussion in 'Trucks [ Eighteen Wheelers ]' started by tallmon, Aug 19, 2015.
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You may have to turn off a/c comp. switch while driving to let ice melt untill it starts air moving, you may need to replace temp control switch at a/c box under dash its just a plug in part.
tallmon Thanks this. -
Sounds like your evap core is freezing up. Does the compressor cycle on/off? If not you could have a faulty evap core temperature switch.
tallmon Thanks this. -
While diagnosing we noticed that the compressor was not cycling. We replaced the compressor limiter switch, it's on the AC line by the radiator. That got the compressor cycling.
Now, it's working better : air flow doesn't completely shut down but seems to be variable.
I bought a new AC temp control sensor and a new evap core temp switch. They were 9$ each.
Can someone tell me exactly where to locate those two items? -
Take cover off A/C heater box with torx screws an find 2 wire temp sensor like the one parts gave you
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Thanks. I'll be replacing the sensors on Monday. This code has popped up:
Cab Climate Control
SAE J1708 (SAE J1587) Data Link
Data erratic, intermittent, or incorrect.
MID 146 SID 250 FMI 2
I'm guessing that's possibly related. Sensor bad? Wire short? Bad batteries (very old).
I also got this one the same day:
Instrument Cluster
Battery Potential (Voltage)
Data valid but below normal operational range (that is, engine oil pressure too low) -
Okay so I took a look under the dash. I found Evaporator Temperature Sensor unplugged. It was still plugged into it wiring harness but it was unplugged from the evaporator housing. Since I had a new one I replaced it and plugged it in as it should be.
The other sensor they gave me is a heater temperature sensor. I can't find where that goes. The center is about 3 inches long looks like a circuit board and the harness is L shaped. Any idea where that one goes?
Obviously the unplugged sensor should have some effect. We will test it out next week on the road.
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