Engine Size: 5.4
Refrigerant Type: 134a
Ambient Temp: 80
Pressure Low: 24
Pressure High: 146
Country of Origin: United States
Hey guys. Recovered,evacuated and recharged the AC system in my F250 yesterday. ID tag on the truck called for 2lb 10oz of 134a. So thats what i put in it. The ac seams to be working fine. I had a vent temp of 48 degrees. Out side temp was 80 degrees. Low pressures side read 24 psi, high side pressures read 146 psi. The pressure held steady,no fluctuation. All readings were taken at idle.
My questions is do those pressures look low to you? I checked the pressures with two different sets of gages. Both read the same.
Pressures seem a little low. But Mitchell lists a similar R134a capacity. As long as you have it charged correctly I would run with it. Recheck pressures when you have a higher ambient. Though 80 degrees should give you a good overall reading.
I think that if you were to hold the rpm st 1200 to1500 for awhile or go on a highway, you'll find the system freezing up. I feel your pressures are too low. Try it as is but if you have reduced airflow from the vents, you're freezing up. As a side note, Fords had bad cycling switches back then.
On first start up after the recharge i did notice the accumulator freezing up but a few minutes later it was normal. Air flow from the vent is on the weak side. Has been that way for a while now. You can hear the fan blowing loud and hard.
What do you guys think is causing the low pressures?
Truck has 200,000+ miles on it. The ac system has never been touched till now. I've noticed a slight decline in performance over the years. So i figured i check for low refrigerant level. My machine recovered 1lb 15oz from the system so i was 11 oz low. I put 2lb 10oz back in it.
Did you replace the drier? This would help alot especially if your drier is saturated.
UPDATE: on low pressures with correct charge.
The evaporator core fins were extremely clogged up with dirt(and a napkin) from years of abuse and use.
At some time or another a napkin had been sucked up in the vent partially blocking off the return air inside the truck.
By removing the fan i was able to get close enough the evap to wash with water first then blow through it with shop air.
AC is working like a charm now. Getting 41F vent temps at Max AC/high fan and down to 37F on Max AC/low fan at idle.Air flow through the vents is WAY better. The compressor is staying on longer now and the the accumulator is no longer freezing up. I did not hook my gauges up (there in my tool box at work) but I'm figuring the pressures are back to what they should be based on the accumulator not freezing up.
Edited: Sat May 19, 2012 at 6:39 PM by Metal Man
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