A/C clutch

Tiny
TAZ2GIZ
  • MEMBER
  • 2001 FORD FOCUS
  • 2.0L
  • 4 CYL
  • FWD
  • MANUAL
  • 90,000 MILES
I have checked all the fuses and relays listed in the owners manual but still have no power to the compressor for the clutch to engage. Is there something I might be missing?
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Saturday, April 29th, 2017 AT 3:53 PM

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Tiny
CARADIODOC
  • EXPERT
Yup. Check the state of charge. All AC systems will be damaged if outside air with its humidity is drawn in if the low side is able to be pumped into a vacuum by the compressor. That can occur when the refrigerant has leaked out. To prevent that, all systems have a low-pressure cutoff switch or a pressure sensor to prevent the compressor from running.

Ford uses AC hoses with quick-connect fittings that go together real fast on the assembly line, but they almost always leak. It is not uncommon to have to recharge the system as often as every other year. Don't go looking for more elusive causes to this problem until the system has been recharged. Chrysler is the only manufacturer that used a sight glass in their receiver / drier to show the state of charge. Ford started using that in the mid '80s, but they don't work. The intent is you can simply add refrigerant from a small can until the vapor bubbles disappear in that sight glass. The problem on Fords is there will still be those bubbles when the system is fully-charged. If you continue adding more and more refrigerant, the bubbles will never go away, and you can reach the point where liquid refrigerant sloshes out of the evaporator and into the compressor. Liquid in the compressor will cause it to lock up, and can damage it.

The other concern is you want just the right amount of refrigerant in the system so the evaporator in the dash is filled half way with liquid. That point, which is where it turns from liquid to vapor, is where it gets real cold, and you want that to be in the dash, not under the hood. Too much or too little charge will seriously degrade the system's performance.
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Monday, May 1st, 2017 AT 5:21 PM
Tiny
TAZ2GIZ
  • MEMBER
How do I charge the system if the clutch won't engage so the compressor can draw in the charge?
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Tuesday, May 2nd, 2017 AT 4:06 PM
Tiny
CARADIODOC
  • EXPERT
Standard procedure is to bypass the low-pressure cut-off switch. Of course Ford does this differently than other manufacturers. The first thing I would try is simply adding from the first can. Set it upright in a pot of hot water to help the refrigerant go in. If enough pressure can be built up in the low side of the system, the compressor should start up on its own.

You can also bypass the "Wide Open Throttle" relay to turn the compressor on. The easiest way to do that is to remove it, pop its cover off, reinstall it that way, then squeeze the movable contact with your fingers to get it started. Once the compressor runs enough to draw in some refrigerant, the compressor cycling switch should keep it running.

Be aware refrigerant is extremely dangerous to work with. It can cause blindness and frostbite.
Professionals wear gloves, safety glasses, AND a face shield.

Also understand you're risking causing other problems when you charge from small cans. If there is any refrigerant in the system now, there is no way to know exactly how much is in there. If you add too much, liquid can spill over and get into the compressor and damage the valves and pistons. If there is no charge in the system now, there is likely air and moisture in it, and that will mix with refrigerant to form an acid that will corrode the metal evaporator and condenser. No professional would ever consider throwing the refrigerant in without first pumping the system into a near-perfect vacuum for a minimum of a half hour, and preferably a full hour. In a vacuum, water boils at 77 degrees and can easily be drawn out as a vapor. That vacuum also helps get the initial refrigerant charge into the system.

Besides corroded metal parts, moisture in the system will also freeze at the orifice valve and stop the flow of the refrigerant intermittently. That is one of the most common causes of the intermittent loss of cooling complaint.
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Tuesday, May 2nd, 2017 AT 5:21 PM

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