AC Compressor has no power
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AC Compressor has no power
I have been doing some AC work on my 1990 F250 351 and had to replace the compressor and dryer. The problem I found when trying to recharge the system was the compressor would not turn on. Using a volt meter the electrical connection showed 0 volts when I had the dial in the cab turned all the way on. I can't recharge without the compressor cutting on so any tips on what to check next would be appreciated. Also, I did check the electrical connection on the dryer and it was showing 11 volts. One other thing was when I turned the dial in the cab all the way up the blower did blow air out the of vents like it should.
New User
Joined: Apr 2009
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I had this problem too. I was told the low pressure sensor is turning off the compressor and to just start filling the unit.
I had the low pressure side up to about 90PSI before the compressor turned on. It works great now! Nice and cold..
John
I had the low pressure side up to about 90PSI before the compressor turned on. It works great now! Nice and cold..
John
Post Fiend
Joined: Jan 2005
Posts: 8,402
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Not an expert but there is a low pressure switch in the system that will not allow the compressor clutch to engage below a set pressure.
I would think either the switch is bad or you are not getting enough pressure into the system.
You will get a more expert opinion if you post the problem on the A/C page further on down from here.
Hope this helps.
I would think either the switch is bad or you are not getting enough pressure into the system.
You will get a more expert opinion if you post the problem on the A/C page further on down from here.
Hope this helps.
New User
Joined: Mar 2009
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You will have to jump the wire going to the clutch on the compressor. Just jump it to the positive side of the battery to make it engage. Once you have some refrigerant in the system then you can reconnect the wire.
Not to nag but be sure you pull a good deep vacuum before charging the system, a little moisture will ruin your day.
Not to nag but be sure you pull a good deep vacuum before charging the system, a little moisture will ruin your day.
Posting Guru
Joined: Jan 2002
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From: Baltimore
The low pressure cycling switch which is located on the side of the accumulator will only close when there is around 47 psi of pressure in the system.
After you pull a vacuum, you should be able to charge the system with at least a 1 lb of R12 with out the engine even running.
To get the clutch to engage you unplug the two wire electrical connector at the cycling switch and jump the wires at the electrical plug together. Start the engine and turn on the AC. The compressor clutch should engage.
If your compressor is the FS6 the system takes 3.25 lbs of R12 and if you removed or lost all of the original oil in the system, you need to add 10 oz of new mineral oil. Example add 6 oz in the compressor (rotate the compressor manually to distribute the oil inside the compressor) 2 oz to the accumulator and 2 oz in the evaporator.
After you pull a vacuum, you should be able to charge the system with at least a 1 lb of R12 with out the engine even running.
To get the clutch to engage you unplug the two wire electrical connector at the cycling switch and jump the wires at the electrical plug together. Start the engine and turn on the AC. The compressor clutch should engage.
If your compressor is the FS6 the system takes 3.25 lbs of R12 and if you removed or lost all of the original oil in the system, you need to add 10 oz of new mineral oil. Example add 6 oz in the compressor (rotate the compressor manually to distribute the oil inside the compressor) 2 oz to the accumulator and 2 oz in the evaporator.
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