Automotive Air Conditioning Information Forum (Archives)

FamilyD on Mon June 28, 2010 11:21 PM

Year: 971
Make: Ford
Model: F 150
Engine Size: 5.4L V8
Refrigerant Type: 134a
Ambient Temp: 80* F
Pressure Low: 46
Pressure High: 205
Country of Origin: United States

It's been several years since I have serviced (deep vac/measured charge) this system. It has always been a fantastic performer during our very humid Tennessee summers. Lately the performance has not been up to par... particularly at idle. We've been in the mid 90's during the day & very humid. The system has been working well enough at speed, but not as well as it's been known to do. It had not been unusual to see upper 30's outlet temps in the morning & at least mid to upper 40's during the day, but not here lately!!!. So I figured the system had lost enough over time that it was time to do a deep vac with a measured charge.

Ambient 80* w/78% relative humidity.
Did a deep vac (490 Microns)... measured charge (exactly 2.0 lbs.)
Idled for about ten minuted... cold right off the bat. About 46* at outlet. Low Side steady @ 46; High Side @ 150
Set up shop fan & held fast idle (2000 rpm), interior fan set @ 2 w/control @ MAX... doors open.
Low Side still held fairly steady @ 46-49 while compressor cycled!!! High Side cycled 150-205 as compressor cycled... Weird!!!

Please... something simple!!!

Joe

Briandl79 on Mon June 28, 2010 11:29 PM

Man I have a lot to learn about A/C systems.

bohica2xo on Tue June 29, 2010 12:22 AM

Put the shop fan away for a bit.

Cabin fan on highest speed. doors open. Engine speed 1500 to 2000 rpm. Run for 5 minutes & record pressures.

If it cycles during a full load test like that check the evaporator air flow. You don't happen to have a 100 lb dog that rides on the passenger side floor do you?

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

FamilyD on Thu July 22, 2010 6:48 AM

B...
Sorry for the delay in my reply... no dog... just the equivalent of a Wal Mart bag!!!
Joe

bohica2xo on Thu July 22, 2010 10:39 AM

As in a walmart bag sucked into the evaporator? That will do it for sure.

The dog comment was not really a joke. I had an F250 apart that was a really clean truck. The evaporator had 5 pounds of dog hair in it. Turned out his wife's sheltie rode around with them laying on or near her feet....

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.