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How cold is too cold ?

Chevelle_nut on Wed July 18, 2012 9:21 AM User is offline

Year: 2003
Make: Ford
Model: Focus
Engine Size: 2.0 sohc
Refrigerant Type: 134a
Ambient Temp: 85f
Pressure Low: 33
Pressure High: 215
Country of Origin: United States

Two part question:

What is the maximum temperature differential from ambient to vent in a car ?

Does low oil charge create lower vent temps ?

I bought the car used so I really do not know the maintenance history, and as nice as having
way cold ice in sunny southwest florida is - if it tanks - wellllll -you know

I am wondering now because after the clutch replacement the thing is cranking out the cold.
This morning I took it out for a ride and the thermometer I left in the vent was reading 30 !
I think the ambient was somewhere around 75 or so. I love the cold air - but if it is going to
burn up compressor I need to take steps now.

The bummer is I have an 8 hr round trip to make today, all highway.

Thanks in advance

Cussboy on Wed July 18, 2012 10:38 AM User is offline

My guess, and just a guess:

to replace the AC clutch, I'd say likely that the whole compressor/clutch was replaced, and the proper refrigerant charge added. That is good. I think your pressures, and the cold temperatures when 75F seem reasonable. Happy driving.

Was your old AC clutch slipping, bearing bad, whatever? That could also have been a source of poorer AC performance then.

ToyMR2 on Wed July 18, 2012 2:20 PM User is offline

I would agree with Cussboy. If the you had clutch serviced at a shop, you could bring it back and ask the shop. It's probably been filled with correct amount refrigerant. 30 seems cold, but you might just be experiencing the results of a properly functioning system.

Chevelle_nut on Wed July 18, 2012 11:08 PM User is offline

I just did the clutch myself, had a burnt coil and bad bearing.
It runs really cold at the vents, almost too cold.
Is there a normal delta between ambient and vent, and what is max theoretical delta ?

mk378 on Wed July 18, 2012 11:33 PM User is offline

Really the limit is evaporator freeze-up, which generally means unless you're in a desert the vents can't run much below 40 or it's prone to freeze the condensed water on the air side of the evaporator because the metal is below 32. After that happens the airflow is blocked and you don't get much if any cooling. It's an absolute temperature not a relative temperature situation. I think the Focus has a fixed displacement TXV system, which would use some sort of evaporator temperature sensor to prevent over-cooling.

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