No AC, compressor clicking

2001 Ford Windstar 3.8 w/ rear AC, 82,000 miles;

No AC at all after not using AC for about 11 months (it worked great then). The AC compressor now makes a constant metallic clicking sound when it cycles on and there is no cold air or cold AC lines. The clicking sound from the compressor is in sync with rpm (sounds a little like a clothespinned playing card clicking against rotating bicycle spokes - remember that?). Noise stops when I turn off the AC.

-Refridgerant pressure on low side (line by receiver/dryer with gauge?) measured 0 psi with el-cheapo interdynamics guage. Added one 12 oz. can of R-134a refridgerant (at operating temp, AC on) which bumped low side to 60 psi. Still no cold air or cold AC lines. Compressor still clicking when turned on.

-Checked refridgerant pressure on low side again a few days later, back to 0 psi. Added more refridgerant (this time with "STOP LEAK") for about 20 seconds which bumped low side to 100 psi! Still no cold air or cold AC lines. Compressor still clicking when turned on.

Bought refridgerant with UV leak detector. Assuming pressure is gone again tonght I guess I'll try the UV leak detector but I'm wondering if anyone has any info on clicking compressors or suggestions.

PS: Various Ford Dealers say:
-Sometimes compressors click when low on freon (on mine the clicking gets louder with more refridgerant)

-As long as you use car you don't have to run AC in winter to condition the seals because compressor cycles on during defrost cycle(?).

-FWIW, Phone Quotes - car unseen:
1) $1043. + tax. [New compressor & drier & orifice tube + refer oil + evac & recharge + labor.
Dealer service guy says: "pluuuus we'll probably have to replace the drier."

Me: "Is it common to have to replace the drier with the compressor?"

Dealer service: "Yes.......(forced qualifier) depending on if system needs to be flushed out....from metallic particles...due to failed compressor."

Out of four dealers, he's the only one that mentions needing to replace the drier and when he calls back with the above quote he laughingly says "the other dealers should know that the compressor is not warranteeable without replacing the drier...could be contaminated with particles and moisture"].

2) $875. + tax. [New compressor $388.68.+ refer oil + evac & recharge + labor]

3) $839.85 + tax. [New compressor about $500.+ freon $70. + labor $269.85 (3 hrs. labor x 89.95 per hr.) of course their parts guy quote me $337.98 for the compressor]. :evillol:

4) $700. Parts & Labor (off the top of his head).

Many thanks in advance.

You will want to take it to a shop that will determine WHERE the leak is.
This spring....I had my first A/C issue with my '96....at 183K miles.
I took it to my indepenant shop.....and they used a "sniffer" to check for leaks around the compressor, etc....and could not get any reading of a leak.
The recharged the unit with a leak detection dye in the charge.
Told me to come back in a couple weeks....as it was still cold outside......
They looked.....and found that the leak was from the evaporator coil.....which is inside the passenger compartment.....not a fun job for them to replace.

My point being...find the leak location before replacing anything......my compressor was fine......and did not need replacement....and would not have done anything to cure the problem.
It is possible that it is only a seal at a pipe/hose fitting.....(I like to hope for cheaper solutions first).


They also had to replace the relay that engages the A/C compressor clutch.....as it would not stay engaged.....but that was a separate problem from the leak.....very likely caused by the constant cycling caused by the low charge of the A/C system.