Service Repair | ||
Black lights aren't just for posters Ford, like many manufacturers, adds dye to its A/C systems at the factory. In Ford's case, it is in the form of a wafer inside the accumulator. That meant I could plug in the black light and check for any sign of leakage. I couldn't readily see either evaporator, but in the lines and components I could see, there were no "bright yellow" dye stains that would indicate a leak. I still hadn't heard any noises that shouldn't be there, but remember, it was a reasonably cool day. Total system pressures, and therefore compressor head temperatures, were lower than they would have been on an 80- to 90-degree day in traffic.The symptoms and test results I had at this point made me believe that there was a problem with restrictions in the system, and those restrictions are typically caused by one of two things: a desiccant bag that had blown, or a compressor that was eating itself. I recovered 1.31 kg of refrigerant from the system, and the specification for this car is 1.59 kg. Does that mean it was low? No, most recovery machines will recover no more than 80 to 90 percent without a deep vacuum that our machine does not measure. Refrigerant will mix with the oil in the system, and it can take a deep vacuum of 30 to 45 minutes to coax out. It was within 80 percent of spec, and knowing my equipment, I felt again that loss-of-charge was not the issue here. I was dying to see what the orifice tube was going to tell me — and as you can see from the photos, it told me a bunch. It's been a while since I've seen one so plugged and still able to meter correctly. If it hadn't been for the fluctuating pressures and the long time it took for the pressures to settle after shutdown, this could have been sent down the road as OK. I guess that confirms the noise my customer was hearing: The compressor was tearing itself up. Where else did it go? Seeing all that debris trapped in the orifice tube, I had a good idea of what I'd find at the rear expansion valve. I had to replace the actuator anyway, so I accessed the casing and removed the valve. Sure enough, it, too, was plugged with metal debris. There are two critical factors to maintaining a healthy compressor: charge quantity and oil quantity. If the charge is too low, even by as little as 10 percent, oil flow will be reduced significantly. If the charge is too high, head temperatures in the compressor will be too high. And oil quantity is self-explanatory — you wouldn't run your engine with too much or too little oil, would you? Because it looked as if the charge quantity was OK, it was time to remove the compressor and take a look. With the compressor off, I held it over a graduated container to measure its oil level so I could compare it to specification. No oil — and I mean no oil — came out. The compressor itself looked fairly new, and the customer confirmed that it had been recently replaced. OK, I think we have all the information we need now to fix this Mountaineer. The repair While Ford does allow flushing of the condenser, the procedure calls for special flushing equipment to perform correctly. Even with flushing, the passages in today's condensers are very small (about the size of a toothpick) and have multiple flow paths, making it a likely possibility that some debris will remain to infect the system later. Installing inline filters is an option, but because of the amount of debris I was finding in the system, the customer agreed to my recommendation for replacement. I did flush all the lines, as well as both evaporators. I felt that the orifice tube and expansion valve had stopped the majority of the debris from entering these components. I also installed a new compressor, and replaced the accumulator (which can't be flushed), orifice tube and expansion valve. With a fresh oil and refrigerant charge, the system performance was again tested. Gauge readings were now stable, and both front and rear ducts were blowing cold enough to keep the passengers comfortable. Heck, they may even have to wear sweaters! Pete Meier is an ASE CMAT, member of iATN, and full-time tech with CarMax in Tampa, FL. He started doing oil changes and minor repairs more than 30 years ago and brings a variety of experience to bear. His current job handles all manufacturers' lines, and "provides me constant opportunity to learn something new." Diagnosing electrical and drivability problems are his favorite challenges. |
