A/C torubleshoot, help please

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May 2, 2011 | 03:43 PM

dougsbart

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A/C torubleshoot, help please

2005 F150 5.4L A/C stopped working. All fuses are good. If i jump the two inboard terminals on the relay under the hood my A/C comes compressor engages and A/C works. The relay seems to be good, so where do i go next? The relay has no diagram on it so i do not know which side is coil and which side is "contact/switch" but if i plug it in i can feel it "click". How do i definatively test this relay and if it is working can anyone clue me in on next step to troubleshooting. Thanks in advance.

May 2, 2011 | 06:59 PM

2Fords1Jeep

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From: Southern New England

If the system has a refridgerant leak and the pressure is low the compressor will not energize.

May 2, 2011 | 07:15 PM

n5926g

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From: Hernando Ms

Chances are its low on refrigerant as suggested.There are two pressure switches in the system,one is on the low side,and the other on the high side.IF refrigerant is low,the low pressure switch will "interrupt" current flow to the relay,and keep the compressor turned off.This is a protection feature.Im sure you have R-134A.My suggestion is to either have a professional check the charge,or you can get one of the "recharge" cans with a guage from most any auto parts store.
A/C systems usually "leak" a minimal amount of refrigerant over time,it has lubricant in it,and this helps lubricate seals,and bearings.If you have a big leak however,you should see some signs of "oily residue" on hoses,connections etc.Bypassing the relay is not a good idea to do for any length of time,since comprssor damage could result.

May 3, 2011 | 08:13 AM

dougsbart

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Low side is further back in engine compartment near dryer, correct? Not the connection by the washer fluid? if so the R134 is charged sufficient according to gage. any other suggestions? I am jumping the relay now to have ac (it is hot here) but the line on the low? side freezes after an hour or so i have to let it thaw. when i jump compressor it blows very cold air.

May 3, 2011 | 05:49 PM

n5926g

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From: Hernando Ms

I cant answer that question,I CAN tell you that(IF memory serves) The LOW side is the larger of the two lines.Conversly,the High side is smaller in diameter.High side plastic cap should be red,low is blue.....

May 3, 2011 | 06:32 PM

Carpainter29

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From: Sioux City, Iowa

You have a bad cycling switch. It is freezing up because the compressor is always running.

May 3, 2011 | 06:46 PM

dougsbart

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N59 the can of 134 I bought only fits on the smaller of the two(nearer the dryer back of engine compartment). Carpainter i thought the freezing was due toe jumping across the relay?