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  Misc. Information

 CLASSIC CASE   By Paul Weissler   - Back to Index Page

The compressor on the 2004 Crown Vic failed and the technician saw contamination, so (he said) he “replaced every component” with the OE parts (supposedly including condenser, evaporator and every line and accumulator)

During assembly, he added oil to each, and finally charged the system (accurately of course). He ran the A/C and the gauge readings started oscillating. He found the orifice tube loaded with metallic debris, after just seconds of operation. He replaced the compressor twice more, along with accumulators and orifice tubes, and sadly got the same problem each time. With a fourth compressor and assorted other new parts, the failures seemed to have stopped.

We weren’t there, standing by the technician’s side, to document everything he claimed was done. If the gauge readings were jumping, the problem recurred in minutes, and the orifice tube was found to be loaded, debris still was in the system. As we pointed out, when all replacements aren’t done in one job, debris may move, and create a blockage.

Ford has long advocated flushing the evaporator, hoses and lines, and as we said earlier, also accepted the idea that a late-model condenser has such small passages that it probably can’t be flushed very well if there is catastrophic failure of the compressor. But let’s review exactly what Ford recommends:

• After recovering the refrigerant, disconnect the refrigerant hoses or lines from the heat exchanger(s) to be flushed. Remove the accumulator or receiver-dryer, expansion valve or orifice tube and hoses with mufflers. Yes, after you find a failed compressor, you take off all these parts before you go further.

• Attach the Ford-approved flushing machine or one you know does an equivalent job, following the instructions and using one fresh gallon of the approved solvent (or a reputable terpene solvent with similar vapor and other characteristics). Ford prescribes a back-flushing procedure, and points out that you’re not necessarily trying to get out just particulate debris, but oil that sludged from overheat.

• Run the flushing solvent through the heat exchanger for at least 15 minutes, more if there’s likely to be a lot of debris.

Then air purge for at least 30 minutes. Ford warns: ”Failure to successfully remove all residual solvent within the component can result in system damage when reconnected and (the system is) operated.” Never shorten the air purge, ever on any machine.

• If the problem was a failed compressor or desiccant, replace the accumulator or receiver-dryer, the orifice tube or thermal expansion valve (or clean or replace the TXV screen) and hoses or lines with mufflers.

• “If A/C system contamination is extensive,” Ford recommends using a pancake filter kit, installed with auxiliary hoses in series with the condenser and its outlet line fitting. Run the A/C; engine idling for several minutes at 800 r.p.m., then for several minutes at 1000 r.p.m. and finally (for an hour) at 1200 r.p.m. Then discard the filter. The appeal of this filter is that it doesn’t require cutting into a line for a permanent installation, but remember it’s been validated only to follow the Ford flushing procedure on Ford vehicles.

Adding a suction side screen and a permanent in-liquid-line filter is not required by Ford, but there’s no objection to the extra protection. The Ford flush removes virtually all oil from components, so remember to add the specified amounts, as noted earlier in this report.



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