Last year The A/C unit in my '85 z28 5.0 was serviced. Everything recharged and running great. Towards fall, I could hear the bearings in the unit rattling around. Short of putting wear and tear on the unit over winter, I took the belt off. In this 98 degree heat wave here I put the belt back on. Switched the lever to max a/c the pulley turns but the unit clasp in from that grabs onto the pulley, isn't engaging. Fuse is good. All connections good. What goes on?

 

No Freon.

There's a low pressure cutoff switch on the side of the accumulator, that shuts the compressor off if the pressure is too low, to prevent freezing up. It will keep the compressor from coming on at all if the system is too low of refrigerant.

Sounds like whoever "serviced" your A/C mostly just "serviced" your wallet. You now need to actually find the leak that they didn't bother to fix, and then buy yourself another $100 worth of Freon for it. I would strongly suggest having someone a little more ethical do the work this time.

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"So many Mustangs, so little time..."
ICON Motorsports

 

an inexpensive and effective way of checking your a/c is to charge it with nitrogen. this way you can give it a full charge and not worry about it leaking out. if it does leak out, it is not as harmful on the environment, and it costs less than a can of freon. another tip, add a little black light reactive die in the mix, let it sit for a day then scan it for leaks. good luck

 

I've got a couple of questions about the leak checking method above. Nitrogen is no problem, but where do you get the leak detector stuff for use with the black light? and is it just a liquid that you pour into the uncharged system? or how do you get it in there?

thanks

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Clem
SCCA TransAm Series Race Mechanic/CrewChief
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1983 Z28 with LG4, 5 speed, and (unfortunately) T-tops
1983 Z28, NO T-tops, (unfortunately) Auto Transmission (hopefully not for long)

 

I don't even feel comfortable using gases and things like that. Are we positive that it's empty, and not something else?

 

where do you get the leak detector stuff for use with the black light?

you can go to any local hardware store and they should carry it. if the system is empty, just pour it into the container. if it is not, just pour some in the hose going from the nitrogen bottle to the canister. after that, just give it a high charge and wait a day or even just an hour. take a black light and just scan the pipes and hoses for anything glowing. if you have a leak and took the time to put some of this stuff in, you will have no trouble finding the leak

 

I don't know if you car still uses R12 or if you have had it converted to R134a. If 134a, it is very easy to get more refrigerant and simple to put it in. It comes in twelve ounce cans, and you can even get cans that come with leak stopping agents, leak finders (red dye), and oil for the compressor all in one. R12 is expensive and sort of hard to find these days. I had been working on making the A/C run right in my '84 (had it blowing 53 degrees on 134a) this past weekend but some woman totalled it on tuesday.

 

To determine if it is empty, you can unplug the low pressure switch on the side of the accumulator and jump the terminals in the connector for a second and the compressor should come on. Don't leave it shorted for long though, because if it is low on charge, it won't have oil flowing around in the system to keep the compressor lubed, and it would cause the compressor to fail. This process will tell you if the control circuit is working. If the compressor runs, the system is most likely empty, but it would be possible that the low pressure switch would be bad.

The best thing to do would be hooking it up to gauges and see what the pressure actually is. If the system is discharged, I would reccomend having it converted to 134a, and the dye mentioned above injected into it (I would get the proper dye for A/C to be sure it is compatible with the oil in the system). It's likely that you have a small leak and may run part of the summer, then you can look to see where the dye is coming from to tell what is leaking.

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Working on:
'84 Z28 LG4 305 with 200,000 original miles!
Added dual elec fans.
145 MPH IROC Speedo
Building 430 HP 350 (ZZ430)
using primarily GMPP parts.
Short block sitting on a stand. (Man, those Fast-Burn heads sitting on it look good!)

Starting to look like the Kicker poster child!

ASE Certified Master Tech