AC, cold on Max, cool on normal ac???
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Senior User
Joined: Apr 2002
Posts: 294
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AC, cold on Max, cool on normal ac???
The other day, my ac started blowing frost through the vents and the temp became cool, not cold. Lately, if i run the ac on Max, the temp runs at 40 degrees or so but on normal ac setting, the temp is 50-55 degrees. However, if i let the system run on max and get down to 40 degrees, i can switch it back to normal and often, the temp will remain at 40.
any idea what's going on? the pattern has existed for some time, but seems to be getting worse. the normal ac setting just isn't cooling like it should.
by the way, vehicle is 98 exped EB 4x4, 5.4 liter
any idea what's going on? the pattern has existed for some time, but seems to be getting worse. the normal ac setting just isn't cooling like it should.
by the way, vehicle is 98 exped EB 4x4, 5.4 liter
Elder User
Joined: Jun 2004
Posts: 679
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From: Orlando, Fla
Well, first off in normal AC, you are drawing air from the outside (that nice hot humid stuff) and using partial existing air inside the truck. Thus your unit is having to cool air brought in at about 90 and try to get it down to 50 in about 3 feet. 40 degrees is a lot to ask of a unit this time of year. Depending on the last service.
Now in Max AC, it is air recycled that is in the vehicle already, about 55 or 60 and only has to lower to that desired 40 by 15 degrees. So much easier on the system.
I would have the AC oil checked, and it wouldn't hurt to have the system evacuated and the orfice tube replaced. Bottom line this is a basic AC evac and recharge.
I suspect the systems ability to stay cool after switching back to normal AC is after being in Max it gets the system chilled and it holds that. It can't do it under initial normal AC more than likely because of the dirty orfice and low oil.
Now in Max AC, it is air recycled that is in the vehicle already, about 55 or 60 and only has to lower to that desired 40 by 15 degrees. So much easier on the system.
I would have the AC oil checked, and it wouldn't hurt to have the system evacuated and the orfice tube replaced. Bottom line this is a basic AC evac and recharge.
I suspect the systems ability to stay cool after switching back to normal AC is after being in Max it gets the system chilled and it holds that. It can't do it under initial normal AC more than likely because of the dirty orfice and low oil.
New User
Joined: Apr 2005
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Discharge temp at your vents inside the vehicle should be 50-55. 40 degrees F is like being inside of a refrigerator, and most evaporator coils will "ice" at 40 or lower. A discharge temp at the vents of 50-55 is perfectly ok in summer months.
Senior User
Joined: Feb 2005
Posts: 459
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From: st.louis, missouri
I agree with High_Horse. The A/C is trying to cool and dehumidify the outside air it is bringing in on the normal setting. Your temps at the vents will be higher. When selected to the Max setting, it closes off the outdoor intake. Thus recirculating the cabin air allowing for lower temps coming out the vents. If your in doubt as to the performace of your system, then take it to a qualified automotive mechanic to have it checked out.
