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Old 09-13-2013, 12:31 PM
Compression Ignition Addict

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6.4 AC issues

08 F250 6.4
Dual zone digital climate

Idle the air blows cold, 40 degree's at vent. Drive some distance, it comes and goes. 50's and 40's at the vent. Stop and idle, back down to 40 or so.

It never gets warm. It just gets cool or cold.

I took it to an AC shop and he checked the pressures and said they are good on the high side maybe a touch low on the low side. Didn't see any reason to add freon. His only suggestion was to evacuate and clean/change the orifice tube. He says that might be closing up when the compressor is spinning faster at driving rpms. He wasn't sure.

Things I have noticed:

1. I drive the truck home 20 min and it's plenty cold enough, let it idle in driveway for 20 min and compressor is on/off cycling. Run for 15 seconds cycle off for 3. Rinse repeat. Always the same cycling pattern. Fairly cold the entire time. I have no idea if it does this cycling while driving. I've read cycling is low freon but I've also read this is normal on our 6.4's.

2..Fiddling with the AC controls seems to make it do something. Switch floor to dash and on and off can make it come back full cold sometimes. Air volume doesn't feel any different. It's just colder. Once it goes cold at idle, it stays fairly cold until I drive the truck.

3.. a few times I've had it on recirc and then select normal (outside air) vent and the recirc is obviously still on by the sounds the fan is making. It's a louder fan and more volume sound. The couple times this has happened the AC has been VERY cold. Hit the recirc switch again and you can select between the two like normal but the cold goes back to cool.

any help would be appreciated..

Last edited by shore; 09-13-2013 at 12:36 PM.
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Old 09-13-2013, 01:25 PM
Compression Ignition Addict

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reading pressures is difficult to diagnose... if he just read them at idle, that isn't going to do anything.

sounds like you're low on refrigerant. This would explain it being cold at idle, but cycling at speed.

Have the system evacuated and add the correct amount of refrigerant. My F350 I had to replace the evaporator core behind the dash (not fun) My F250 started doing the same thing, but it ended up being a little piece of plastic hanging one of the schrader valves open. WHEW!
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