AC Charge
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Junior User
Joined: Mar 2007
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From: Ohio
AC Charge
My 97 150 5.4 excab with 120K, is throwing cool air 55F in 85F ambient. The compressor runs without cycling. It pulls down to about 27 than slowly climbs up to about 45 but does not cycle in the drive. It has never been apart and only served by a qualified tech about 6 years ago without adding any freon.
Question, Too much charge? Too little charge? Air in system? other causes?
Question, Too much charge? Too little charge? Air in system? other causes?
Senior User
Joined: Nov 2003
Posts: 108
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Are you saying it drops down to 27 degrees? The low pressure switch sould kick it off before it gets that low. The lower the temp. of the air coming into the truck the lower the refrigerant pressure. So if it gets that cold then maybe your low pressure swith is bad. If the swith is bad your evaporator will freeze on a long drive and you will feel warm humid air coming from your vents.
If it's low on refrigerant your compressor will cycle off and on and you wont get air colder then 60 degrees or so. That could happen if you have a leak.
If it's over charged then the compressor will cycle off and on when the pressures get to high. The over charge can only happen if someone has worked on you truck recently. Same for air in the system. It's a pressure system so air can only get in when it's out of refrigerant.
Hope this helps.
If it's low on refrigerant your compressor will cycle off and on and you wont get air colder then 60 degrees or so. That could happen if you have a leak.
If it's over charged then the compressor will cycle off and on when the pressures get to high. The over charge can only happen if someone has worked on you truck recently. Same for air in the system. It's a pressure system so air can only get in when it's out of refrigerant.
Hope this helps.
Hotshot
Joined: Jan 2004
Posts: 19,763
Likes: 1,082
From: St Louis
Are you saying it drops down to 27 degrees? The low pressure switch sould kick it off before it gets that low. The lower the temp. of the air coming into the truck the lower the refrigerant pressure. So if it gets that cold then maybe your low pressure swith is bad. If the swith is bad your evaporator will freeze on a long drive and you will feel warm humid air coming from your vents.
If it's low on refrigerant your compressor will cycle off and on and you wont get air colder then 60 degrees or so. That could happen if you have a leak.
If it's over charged then the compressor will cycle off and on when the pressures get to high. The over charge can only happen if someone has worked on you truck recently. Same for air in the system. It's a pressure system so air can only get in when it's out of refrigerant.
Hope this helps.
If it's low on refrigerant your compressor will cycle off and on and you wont get air colder then 60 degrees or so. That could happen if you have a leak.
If it's over charged then the compressor will cycle off and on when the pressures get to high. The over charge can only happen if someone has worked on you truck recently. Same for air in the system. It's a pressure system so air can only get in when it's out of refrigerant.
Hope this helps.
..those are low side pressure readings...
Senior User
Joined: Nov 2003
Posts: 108
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Your looking for about 35lbs on the low side priessure at a fast idle. It should stay there as long a you keep the idle speed constant. If it wont hold the pressure then you may just have a suction valve wearing out in your compressor.
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Junior User
Joined: Mar 2007
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From: Ohio
Update
I took it for a short trip later in the evening after the outside temp had dropped below 80F and it cycled quite well and the duct temp dropped to 45F and after 30 minutes it hit 40F so it seems to be OK at this point,
Thanks for the comments
Thanks for the comments
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