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1987 300D A/C just quit - anyone have a schematic?

Was driving the other day and it just suddenly quit and started blowing ambient air.

Got home and tried listening for the compressor engaging when I dialed-up 'max cool'. No clutch click. Checked pressure - don't see anything in the sightglass because there's no flow but I have >140PSI in a hot system - it SHOULD be enough pressure for the cutout sensor. Fuse (#7) is okay because the blower runs.

I don't have my metering handy so I can't start electrical checks for a couple of days. There was oil the last time I burped the high-side connector - looked reasonably clean. No visible leaks - I shouldn't have lost any oil. Had UV tracer in it from last year and I see nothing under UV light. Can't add oil or tracer now since I can't get a pressure drop. It's an R12 system, with a rebuilt R134 compressor, running 'Freeze-12' refrigerant (which is good for both '12 & '134 systems & seals & pressures & oils).

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My Haynes book sucks when it comes to A/C - you can tear down brakes & steering & suspension and do other things that can kill you if you've screwed up, but they say A/C is dangerous black magic and should only be done by pros. Not even a schematic. F-'em.

Any help greatly appreciated. Thanks.

Reply to
sol
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First of all, you must be clear on what you are trying to say. It is kinda rambling.

Was the system blowing icy cold before it completely stopped?

Shine the flashlight at the compressor to see if it is spinning. The front of the compressor is stationary if not moving

If you don't have pressure gauge, how can you be sure it has 140PSI? Beside that 140 PSI on non working AC is very high.

Low side pressure when AC is running, aux fan running, windows closed and interior cool should be at 30PSI constant.

Pull out your AC fuse and repalce it, check your overload relay fuse and reset your Klima relay to knock out any corrosion on terminals.

Reply to
Tiger

I shall type slower for you:

The clutch is not engaging. The compressor is not spinning. The fuse is good because the fan/etc is working. I HAVE a pressure gauge or else I wouldn't have been able to check the pressure.

140PSI isn't all that high for a hot system (it's summer here) that has just been running. (R12: 140PSI == ~110ºF)

"klima relay"? THAT's why I'm looking for a schematic.

.> First of all, you must be clear on what you are trying to say. It is kinda > rambling.

Reply to
sol

Clutch not engaging means a couple of things.

  1. Klima relay, behind battery cover.
  2. Pressure too high
  3. Overload relay
  4. Ignition switch

What is the pressure for COLD static system?

140PSI in R12 is +110 degree F... not negative. Otherwise, you have a cryogenic AC system.

Now you can fix your AC system without further assistance.

Reply to
Tiger

Tiger ha scritto:

Chapeau, Tiger! You're extremely polite. And quiet...

Reply to
Cordy

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