Recently my dad bought a 2005 Mercury Montego (same as Ford Five Hundred) with 66k miles. When he first got the car the a/c worked fine, but now it has stopped working. He was able to get it to work on the highway, but not when at idle. I have confirmed that the compressor is engaging, both radiator fans are spinning, the blend door works, put a leaf blower on the condenser to simulate cruising speed, and revved the engine and nothing worked. I have not and am unable to check charge psi, as I dont have the tools. Right now I am leaning towards compressor failure, as it is covered in uv dye/oil. Any other ideas?
UV dye and oil pretty much means the compressor seals have failed. Odds are whoever sold it knew the thing was leaking like the Titanic and did a quickie charge on it. That lasted long enough for the transaction to finish. That’s a very common thing to do.
Right now a gauge set needs to be put on it. Odds are the compressor is good (sort of) but the system is low charge due to leakage.
Seals can be replaced but replacement of the compressor is the better altenative. That means a new accumulator and orifice tube also.
The vehicle was bought knowing that the a/c compressor may be leaking, but it was over $1000 below book value and in great condition with no rust so it was worth it. My dad plans to eventually take it to a shop where he knows the guys, so they can hook up a gauge set and determine the problem.
Please let us know what the repair cost was. Somehow I think it may be more than $1000.00
I think your idea to take it to a shop who has the necessary experience and equipment to diagnose AC problems is spot on. AC repair, especially in newer cars like yours isn’t something for the typical driveway diy’er to attempt. The systems are very sensitive to the amount of refrigerant, and just a little too much, or a little too little can cause all sorts of problems, some of which – esp on the too much side — are very expensive to fix. I expect there are a lot of 10-15 year old cars that go to the shredder due to AC problems that proved uneconomical to repair.
If you are mechanically inclined, you could try to rebuild the compressor. Depending on the type, a kit runs between $20-$50. It’s actually not that hard to do if the damage is confined to gaskets and seals. .
You might check to make sure the blower fan is actually running, my experience fine on the highway, the car would get warm at stoplights. Due to a bad variable resister speeds 1 and 2 were not working, enough natural flow on the highway to keep us cool. I relaced the $18 part and viola, cool at stoplights again
Air is coming out forcefully, no restrictions there, as well as working at lower fan speeds. It will switch to heat so the blend door is operational.
If the compressor is engaged and the accumulator is not sweating a bit and cold to the touch odds are the system pressure is low.
The connection of a gauge set with the engine and A/C off can reveal if there’s a low refrigerant issue. The static pressure on both low and high side should be in the 120-125 PSI range.