I could use some advice on my AC system. I can see the clutch engaging, but there is no cold air. Here is the story as to how it got to this point:

I noticed ac was not very cold so decided to try one of those DIY cans.
It would not fill at all for a long time, then all of the sudden, it overfilled it very quickly.
I drove it around the block and ac quit altogether.
I took it to a shop to have them evacuate and refill the refrigerant, and they told me the compressor was bad.
I searched a bunch of threads on NAM and determined my ac clutch coil was bad, so I bought one and replaced it. Cool ac again!
I drove around town, very hot out, for about 50 miles. When I came to a stop outside my house I heard a sound from the engine like woo woo wooo wooo woooo woooooooo..... and the ac blew hot air again.
Like I said, I can see the clutch spinning when the ac is turned on, the low speed fan comes on as well, but it is not working.
I put the gauge on the pressure line that came with the refill kit, and there is no change in pressure between the compressor engaged vs not engaged, and I don't really notice any engine rpms drop when it "engages" now.
Also, there is some black gooey fling around the clutch, which I think is the rubber from the outer clutch plate melting and flinging off.
I have read through dozens of ac issue threads on NAM, but haven't found much. I had pretty much decided it must just be the compressor has died, but I've read a few threads where people replace the compressor, it engages, but they still only get hot air, which worries me.
When it comes time to do the work, I will have to take it to a shop to drain, and later refill the system, but I will be replacing the parts myself. Is there anything else that could be the issue? I've heard the metering valve is extremely difficult to access.

Thanks!

 

Your problem description sounds just like mine, except for the black goo. Please keep us informed as you work through this problem.

 

It does sound like the compressor, so you should replace it. But you also want to replace the orifice and the accumulator/dryer at the same time.

You can do all this yourself and same some money and then take it back to the shop and have them evacuate and charge the system.

 

The black gooey stuff can be belt material, check the belt and see if there are signs of rubbing. The compressor clutch kits that were available for awhile weren't really a quality thing, and would eventually fail again. I would be more inclined to replace the compressor all together with something that has a warranty, either from the dealer, or something from O'reillys, which we've had great luck with.

If the system is underfilled the compressor will run near constant to build pressure, and won't run at all if over full. The DIY cans don't give you the necessary gauges to properly meter what is really going on in the system, you need to buy a set of manifold gauges, or have a shop with an AC machine do the job.

It is recommended to replace the receiver/drier whenever the system is opened, but not entirely necessary. It's cheap enough and easy enough to do though, so I would recommend it.

Nick
Detroit Tuned

 

Nick: is replacement of the expansion valve a DIY?

 

I've never seen one fail on these cars, the majority of problems I see are either leaks or a failed compressor clutch.

That said, you'll need to be able to evacuate the refrigerant, and it will be a bit of working behind the engine on the bulkhead, and working underneath the driver side of the dash.

 

The reason that I ask is that I have seen some compressor warranties contingent upon replacement of the expansion valve.

 

Bet the black-goo is oil and compressor parts going out of a bad seal....
Ac compressors are usually made of carbon....when they wear from not enough oil, or too much psi, bits flake off...and a few miles later, it lets go...the compressor part sheers off, or the pump tears itself apart.

 

The black goop is definitely melted rubber from the outer clutch plate. I'm sure it's not the belt, or the compressor innards. I actually don't think the goo has anything to do with the problem. I think it's just the clutch rubbing while it is disengaged because the surfaces were a little messed up from taking it apart.
Is there any reason a compressor could be engaging, and still good and not produce any cooling when the system is properly filled?
I'm also curious about the necessity of replacing the expansion valve. It's only another $50, but I haven't found any kind of how-to on replacing it yet, and from what I've read, it's a real pain to do. If it's not really necessary, I'd rather avoid it.

 

The "expansion valve" or orifice tube should be replaced. Since when the compressor fails it often releases debris into the system, the orifice will get clogged. If so, you will ruin the new compressor and your system will still not work.

 

Do you know if anyone has done a walkthrough on replacing one? I don't have the manual and I haven't seen anything on how to do this anywhere.

 

Here's an interesting update: The clutch is melted. The rubber portion of the outer plate, the part that holds the two halves together is melted and flung all over the place. Which is why I can see it spinning, but the compressor didn't seem to be functioning. I noticed a little bit of melted plastic fling, and a little bit of galling when I was replacing the clutch coil, but I was eager to get it back together, and didn't even know where to find a replacement clutch. It could be that when I overfilled the system the compressor had more resistance, causing the clutch to slip, begin to fail and the coil to overheat and short out?... After the coil replacement, the clutch held on for another 50 miles or so before it threw in the towel as well. Either that, or the compressor is having issues, causing the clutch to continue to have problems. The compressor shaft didn't spin easily by hand when I had it apart, but it was pretty easy to turn with a wrench. It doesn't seem like there would be enough friction there to cause the clutch to slip and melt, but I don't know how much friction there should be on a compressor. Any advice? At this point, I suppose I should just give in and replace the compressor and drier. I'm thinking the compressor is still functioning, although it may have something wrong with it. At any rate, I'm thinking it's unlikely that the compressor innards are scattered throughout the system waiting to cause future damage to a new compressor since it was cooling fine up until the clutch went out. And thus I probably don't have to replace the expansion valve, which I've only read terrible things about doing.