1967 427/390 air conditioning

[Al M.]

My a/c compressor keeps binding every time I turn on the a/c causing the belt to slip and the fan to stop turning.. I've had the compressor rebuilt by classic auto air and my mechanic has intentionally put in a light charge of coolant. It runs fine for about 30 seconds then starts to bind. Any suggestions?

[Lynn H.]

Re: 1967 427/390 air conditioning

My a/c compressor keeps binding every time I turn on the a/c causing the belt to slip and the fan to stop turning.. I've had the compressor rebuilt by classic auto air and my mechanic has intentionally put in a light charge of coolant. It runs fine for about 30 seconds then starts to bind. Any suggestions?

Al,
When you say "bind", and the belt slipping, are you sure that's what is going on. If the compressor (or clutch)was to lock up, the belt would be smokin'. Is it possible the clutch is engaging and disengaging. If there is not enough gas in the system, it will "short cycle", causing the clutch on the compressor to kick in an out repeatedly. It should have a full charge of freon to work properly.
Lynn

[Keith G.]

Re: 1967 427/390 air conditioning

Do you have the short belt on that runs from the crank to the fan only, I had to ask. I bought a ac'd 427 that had a long belt that ran the ac, fan and crank, and no short belt. that did not work, the ac belt is only on the ac and fan. Then the alternator belt helps runs from the fan and crank also, so that means the fan pully has 3 slots.

[Dick W.]

Re: 1967 427/390 air conditioning

Al,
When you say "bind", and the belt slipping, are you sure that's what is going on. If the compressor (or clutch)was to lock up, the belt would be smokin'. Is it possible the clutch is engaging and disengaging. If there is not enough gas in the system, it will "short cycle", causing the clutch on the compressor to kick in an out repeatedly. It should have a full charge of freon to work properly.
Lynn

No cycling clutch in 1967. CCOT came about about 1977?

[Lynn H.]

Re: 1967 427/390 air conditioning

No cycling clutch in 1967. CCOT came about about 1977?

I stand corrected, shows how many early A/C cars I've had. Did they "cut out" if they got low on freon?
Lynn

[Larry M.]

Re: 1967 427/390 air conditioning

I stand corrected, shows how many early A/C cars I've had. Did they "cut out" if they got low on freon?
Lynn

No.....but I believe that some had a superheat switch that would de-energize the compressor clutch at high compressor temperature (or pressure??).

Larry

[Dick W.]

Re: 1967 427/390 air conditioning

I stand corrected, shows how many early A/C cars I've had. Did they "cut out" if they got low on freon?
Lynn

Unfortunately no. If you developed a major leak and lost your oil charge, they would keep running until they self destructed

[Jack H.]

Re: 1967 427/390 air conditioning

First use of the superheat switch was in 1972. Plus, the engine harness changed to accommodate that feature with the wiring to the compressor being slightly different. I don't think that's the answer here.

[Jack H.]

Re: 1967 427/390 air conditioning

From your description, I think I'd be somewhat leery of the mechanic...

Where am I coming from? As Dick stated, the compressor runs 100% duty cycle (compressor did NOT cycle ON/OFF). Second, it's the refrigerant in the system that carries the mineral oil (some in the compressor, some in the receiver/dryer, Etc.) to lubricate the vital moving parts.

If the system was intentionally 'short filled' on R12, I'd be asking WHY???? Without the proper amount of oil moving through the A6, expect 'er to heat up and begin to sieze!!!

That's why the super heat switch was introduced in '72. It prevented those compressors who'd blown a front bearing/seal from going RED HOT and self-destructing.

When the A6 case temperature reached a critical point, the super heat switch would kick in and 'starve' the compressor's clutch for electrical power. That would 'free wheel' the compressor and keep it from overheating to the melt-down point!

Last, some who rebuild compressors ship them filled with oil while others ship them dry. And, if the receiver/dryer was changed, replacements typically come WITHOUT oil.

Bottom line, the A/C mechanic has to know the parts he's working with and assemble them properly! I can't think of a competent refrigeration tech who'd INTENTIONALLY 'short fill' an A/C system...

If there's a lack of confidence in the system's seal integrity and a fear of losing R12, then fill the system with an 'exotic' refrigerant (R12 substitute). Run the AC for a SHORT period, just long enough to confirm system seal integrity, then dump the substitute and re-fill with R12...