Engine Size: 5.0
Refrigerant Type: R12
Ambient Temp: 91
Pressure Low: 40
Pressure High: 350
AC system was replaced when I bought this truck 7 years ago with OEM Ford parts and refilled with R12 by a ford mechanic. Has worked great up until last summer. Wasn't cycling on last summer. Got around to it now, pulled the low pressure cut off switch plug to check connection and replaced. Now it cycles but not very cold (60 degrees at the vent on max/high). The accumulator/drier isn't even cold to the touch (normally ice cold and dripping). Hooked up hoses to check readings and came up with high 30's on low side with 260 on high side at first. Got the RPMS to 2000 placed thermometer in front of condenser and in main outlet, rechecked pressures and got 40/350. Ambient temps 91 with high humidity and only 60 degrees blowing out the vent. Compressor is cycled on but not cycling off. Shouldn't be overcharged as it hasn't been touched in over 7 years. Clogged drier?
Worn out fan clutch. Does it cool better when the truck is moving? The charge is probably also a little low, but there's a condenser issue for sure.
Thanks. I replaced the fan clutch 2 years ago. It seems to work fine. I thought the pressures are too high for a low charge? So you're thinking the condenser is clogged, not the accumulator/drier? Any way to check these things without just replacing parts?
Thanks alot guys. Checked further into the fan clutch and sure enough it wasn't functioning properly. Now it's cooling to about 45-50 at the vent, pressures are 30 on the low and 250 on the high at 2000rpm (85f)
So it seems my problems have not been completely eliminated. After driving this the AC starts off cold, then goes warm, compressor is still engaged. If I turn the AC off then back on a little later it does the same. Checked pressures again and at 2000 rpm the low side was about 30 and the high side about 200-220 ambient temp was 74 vent temp about 50-55. Misted the condenser and all pressures dropped, and cycled up and down, low would drop to 20, kicking off the compressor, high would drop to low 100's, and no cool air out of vent. Pressures would climb back up kicking compressor on then drop again. Does it need recharged?
When it runs warm, pull over and open the hood, leave the engine and the A/C on. See if there is ice on the receiver and lines. If there is, the evaporator has frozen up. This is caused by the cycling switch being stuck on. When you turn the A.C off for a while, the ice melts and cooling can restart, until it freezes again.
Also make sure that the heater is shutting down when you set the dash control for full cold. Heater and A/C fighting each other, the heater will win.
Since it gets cold once, there is enough refrigerant. Either there is enough to make it cold or there isn't.
Edited: Mon June 02, 2014 at 7:59 AM by mk378
Nope, no ice on lines, accumulator isn't even very cold the the touch. Used to condensate like a river when it worked well.
What are the pressures when it runs warm? I can't follow your post very well. You talk about cycling, but you also say the compressor stays on. I'm only interested in when it runs warm. With an intermittent problem you have to test while the problem is actively occuring.
Sorry for the rambling. I checked it last night after it had sat a few hours. Ambient temp was 74. At 2000rpm Low side reading 30, high side reading 200. Vent temp was about 55. When the AC goes warm both pressures increased, low was about 40 and high was about 220. No cycling occurs-compressor stays on. The only way I got the compressor to cycle was by misting the condenser. That is when all pressures dropped and compressor cycled on and off while pressures climbed (compressor off) then dropped (compressor on) and no cool air.
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