Air Conditioning System

General Information
Finding Leaks

General Information

Its rare for an A/C clutch to go bad. Could you describe exactly whats wrong? Does it not engauge, slip, scream, open coil? IF the clutch is bad, the compressor has to come off. A/C shops today generally have recovery machines that can salvage your new charge of Freon gold and squirt it back in after repairs are made. Hopefully its just a disconnected clutch cable. Oh yes, the clutch coil grounds thru a switch on the back of the compressor and you may wish to see if that has come off. New (replacement compressors sometimes don't have this switch) and the lead has to be cut, a lug soldered on, and grounded to the nearest convienient bolt.

From: Tin Man

"Its rare for an A/C clutch to go bad."

I must disagree with this. Many drivers, not knowing what the "clicking" of an A/C means often run the A/C with low or no refrigerant. This will wear out a clutch in a hurry! And a properly maintained system will sometimes have a clutch go before the compressor. Also, if you run the defrost A LOT or frequently turn your A/C on and off for PEAK comfort, this will wear out a clutch sooner.

From: Robby C. Sperr

Finding leaks

An A/C system that leaks its gas out in a week is a fast leak, not slow, and should be easy for a refrigerant tech to find. The hardest to detect is one in the evaporator.

I use dry shop air to check for leaks in A/C systems and don't understand why that should be a problem. Here are a few methods that I find useful in tracking down leaks; sometimes a combination of these is necessary to locate a sneeky leaker.

  1. 100# shop air- gauge and soapy water
  2. Freon 22- electronic leak detector
  3. Florescent dye- black light

First, I look for the tell-tale film of refrigerant oil that often is associated with a leak. This can be at joints, on the surface of the evaporator or condenser, hoses (weeping or pin holed), or the compressor ends and the center seam. Don't forget the Schrader valves.

On the Fiero, common leak points are the pipe junction in the engine compartment in the far left front corner. Leaking Schrader's are another. The two O rings that seal the manifold to the compressor rear is another troublemaker. Condensers and evaporators shouldn't be overlooked; the condenser is easy, just look at it for the stain of oil. The evaporator can be examined by removing the blower resistor assy. in the forward compartment from the evap. case and have a look- see with a dental mirror and a light.

The shop air is the easiest on an empty system and costs nothing. The system is filled via a gauge set with 100# or so of air and the gauges shut off. I then watch for a pressure drop while testing suspect leak points with a squeeze bottle of soapy water looking for bubbles.

Freon 22 is still available and reletively cheap and the system charged with this stuff and sniffed with a electronic leak detector. This is the LEAST of my choices as the constant beep-beep of the detector drives me nuts; and I don't find it to be all its cracked up to be, but it does work. Stay away from the archaic lighted propane leak detector, they're woefully ineffective and dangerous.

My favorite leak detector is a dye that is injected with the Freon that will glow a brilliant yellow at a leak site when viewed with an ultraviolet light; leaks can be found very quickly with this method. The downside of this is that you have to inject this stuff, cycle the system and then check for leaks, THEN repair the leak, a waste of Freon. I inject this whenever I charge a system so that IF a leak develops, I can go right to the black light.

I had a Buick Riv that had a Freon leak that needed attention every three months and, using the dye, I couldn't find the leak. The GM rep said that quite a few high end GM's had evaporator leaks and to check there. Sure enough, when shining the ultraviolet light into an access hole in the evaporator case, the whole case glowed like it was neon, a rather beautiful sight. Unfortunatly, it took 6 hours to change out that evaporator!

Once the leak has been found, the system is sucked down and recharged, but you will want to make SURE that the system's tight, Freon 'aint cheap. This is a good tine to open the fittings in the forward trunk and inspect the orifice tube for debris.

Tin Man

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