2 much pressure ?
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2 much pressure ?
i have a 97 f-150 and now thats its getting cold i use my defrost all the time . now when my defrost is on the clutch cycles on and off every few seconds . so i tested the pressure and according to the kit i have and the current outside temp it seems to have to much pressure . is it normal to cycle that often ? would high pressure cause it to cycle every few seconds or if i'm reading the guage wrong what else would cause it to cycle so much ? i know low pressure would cause this but the guage that i have said the pressure was high and i thought that the colder the outside temp the lower the pressure . any feed back would be great .
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from the low side 45 psi in 50 degree temp no way to test high side and the clutch is on for about the same time it's off every 3 seconds its either turning on or off . if i take it off the defrost settings then it stops
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R134 static pressure will hold fairly close to ambient air temp as long as the refridgerant is not contaminated. if it is only 50 degrees out, then it is normal to have the clutch cycle on and off. the pressure cycling switch will open the clutch circut every time low side pressure drops below the set parameter. Usally around 20 lbs. with a 50 degree ambient, that does not take very long. did you measure this pressure with the clutch engaged? if not,than the pressure you read was static. try to see how far the low side pressure guage drops when the clutch kicks out.
Last edited by bustech81; Dec 4, 2006 at 09:17 PM.
Hotshot
Joined: Jan 2004
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From: St Louis
With a properly charged system, at 50F, the compressor off cycle should be fairly long compared to the on cycle time.
I'd actually suspect a low charge. However, since there is no high side pressure reading available, can't make a more definite comment. Compressor short-cycling is a typical symptom of this.
Ford's pressure cycling switches typically operate as follows: Closes at 45 psi ascending, opens around 22 psi descending. Readings plus/minus a pound or two.
Steve
I'd actually suspect a low charge. However, since there is no high side pressure reading available, can't make a more definite comment. Compressor short-cycling is a typical symptom of this.
Ford's pressure cycling switches typically operate as follows: Closes at 45 psi ascending, opens around 22 psi descending. Readings plus/minus a pound or two.
Steve
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