Engine Size: 5.4
Refrigerant Type: 134a
Ambient Temp: 100
Pressure Low: 45
Pressure High: 325
2006 Ford F150 with 55,000 miles on the clock.
A/C was working fine 2 weeks ago. Last week it would not get cold. I have had "weak" A/C from this truck since I bought it new so I have had a vent temp gauge since 2006. When I noticed the vent air was not cold I looked at the temp gauge and it showed 60 degrees. I live in Austin, TX and currently everyday is at least 100 degrees. The vent temp of 60 degrees is only when the truck is going 70 miles an hour down the road. When I stop at a red light the vent temp goes up to 65-70.
I rented some gauges and put them on. The pressures are 45 on low and 325 on high sides. The compressor clutch kicks on and off with the A/C button. I also disconnected the high side pressure switch connector and the compressor turns off.
I talked to a friend of a friend that does A/C work. Unfortunately he was not able to stop by today. Since I had already gone over a week without cold air I decided to have a friend evacuate the system and then I cracked it open to look at the orifice tube. The tube filter does have a little bit of metal shavings on it however it is not clogged. I can easily see through 90% of the filter.
Now I don't know what to do. Does anyone have any suggestions? Do I need to replace the compressor because of the small amount of metal shavings? I know I need a new orifice tube and 2 or 3 12oz cans of 134a but I don't know what else I need to do.
I can throw parts at it however I don't have access to evac gear as my buddy did it on the side and got in trouble from his employer. I really only have 1 shot to fix this.
(a) Poor condenser cooling :The condenser must have proper air flow and all fans working properly, if not,the a/c system will loose cooling performance.
(b) Over heating engine :low coolant levels and poor radiators that are clogged or missing cooling fins will cause adittional heat load on engine thus causing poor cooling performance.
(c) A/C compressor clutch problems:excessive wear and increase air gap on compressor clutches can cause erratic operatrion.A compressor clutch that cannot engage all of the time will cause poor cooling performance.
Thank you for the input.
Any advise as to the small amount of metal shavings on the orifice tube? The compressor seemed to have the ability to generate pressures so I don't know if anything is wrong with it or if the shavings are normal.
What you consider a small amount and what I consider a small amount could be 2 very different amounts. Metal in the system is not good. But if you have a "small" amount the system may run for another year. If you simply have a small leak somewhere. Repair it, add some oil. Then run it until it dies.
Well that's part of the problem. The system was not low on 134a. It just stopped cooling very well.
I guess it could be the compressor however I don't know if compressors get weak or if they usually just die. When I rev the engine the compressor does push the high side to cut off (400 or 450 psi cant remember which). Once I lower the RPM the compressor will come back on.
Why are you pushing 400 or 450 psi on the high side??? Are the fans even running? Is the condenser or radiator blocked? You shouldn't be running those kinds of pressures, and the source of that problem needs to be addressed first.
So the pressure should not go higher as the engine revs? I thought that was the entire purpose of the high cut off switch.
The high pressure cutout switch is only for safety in case of abnormal operating conditions (those mainly being impaired condenser performance, overcharged, or refrigerant contaminated with air). It's there to kill the compressor before a hose or relief valve blows. In normal operation it should never cut off. High side pressure should stay below 300 even in 100F ambient.
Edited: Sun July 17, 2011 at 2:05 PM by mk378
Thanks for all the information.
I put a new orifice tube in and I have 10 mins left on (2) 30 min vacuum sessions. After it sits for 10 mins I am going to put 2 cans of 134a in it. I will then see where I am at. I will report back shortly.
Put 2 full 12 oz cans and most of a 3rd 12 oz can in the system. Sticker in engine bay says 34 oz.
Readings at 100 degrees are 34 low and 275-295 high.
Can someone please advise me?
While reading various posts and forums someone suggested misting the condenser with water. I got the water hose out and misted the front of the condenser. I just kind of sprayed off the condenser and then turned the water off. Almost immediately the vent air started getting colder. While reving the engine to 1800 RPM the vent temp dropped to 55 degrees. The gauges are still showing (what I consider) strange numbers. Low was 30-32 and high was 300.
It has not rained good here in months and it's extremely hot. The condenser didn't look overly dirty to me. I also didn't see to many bent fins.
What does everyone think?
Edited: Sun July 17, 2011 at 3:51 PM by flash69
Possibly a bad fan clutch.
You already mentioned debris in the system. So you have to find out why you have higher than normal head pressure.
Things I would look at, over charged system, bad fan clutch, plugged component.
Plugged. As in the condenser passages being plugged from the debris in the system.
Got to finish some of my own chores. Need to get the high side down for it to cool properly.
Sorry I misunderstood.
I was outside checking it again and decided to see if the pressure would go high again. I reved the engine to 4500 and the high side never got above 315. Would the orifice tube cause the high side to get really high? That is the only thing I have replaced.
I went for a test drive and and the vent temps get down to 42 degrees with blower motor on high. I think my problems were a combination of things. I will monitor over the next week.
Thanks everyone for your help so far.
i found this forum while trying to troubleshoot my a/c problem. After reading your posts last week, it was if I had written it. I did everything just as you did. I even have a 2006 King Ranch with the 5.4l. I was experiencing warm air from the vents, it is 95-100 here in Florida. I've always been happy with my a/c until last week when it suddenly acted like it wasn't cooling well. The pressures seemed normal, but I decided to check the orifice tube. It was to my surprise, clean. I thought now what? I evecuated the system and recharged it, 34/205 and suction line cold and sweating, still blowing hot air. I was scratching my head and decided to go for a test drive after I recharged it. Took my wife along and placed a thermometer probe in the air vent, she monitored the temperature and I manipulated the controls. We found that the were sweet spots in the temperature settings that would produce colder air. Then it hit me, the heater was on at the same time, thus explaining the good pressures and the hot air. I placed a vise clamp on the heater hose pinching it closed. Voila!! ice cold air. Did some more searching and found out there is a common problem with these fords. It's called "Blend Door Failure". Google it and you'll see. The Ford design allows the heater air to mix with the evaporator air to provide the climate control. There are two main parts that fail. One is the "blend door" and the other is the "blend door actuator". The parts are not too expensive, however, you have to remove the whole dash to replace the door. You can just remove the center panel to access the actuator. For now, i dont need the heat, so I'm gonna bypass the heater coil. This may be your problem too. If you find that it is, good luck pulling the dash. Once you have it mastered, I'll pay you to fix mine
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