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82gray380 04-26-2008 01:02 PM

retro fitted AC compressor not working
I bought my 1982 389sl during the winter months and never really knew if the AC worked. The P.O. stated, it did when he stored the car away several years ago. Anyways the system was dry, so I bought a retro fit kit to change it over to 134. It sucked up 2 cans of 134, but the compressor will not kick on. I found 2 black wires at a contection on the passengers side inner fender by the radiator fill tank and tried jumper them to get the compressor on, still didn't work. Checked the AC fuse, it's good. There should be some kind of hot wire going into the compressor. The 2 black wires seem to be grounds or a switch. Any ideas or suggestions, before I take it into the shop and get overcharged for labor.

ctaylor738 04-26-2008 07:21 PM

How did it "suck" two cans of R34 if the compressor wasn't working?

82gray380 04-27-2008 12:57 AM

I suppose if the system is empty, there is enough pressure in the cans to force the gas into the lines. All I know is that I have 2 empty cans of 134 that I put into the low pressure side and the clutch on the compressor is not engaging.

ctaylor738 04-27-2008 10:37 AM

Normally when you fill an empty system, you need to jumper the wires that connect to the pressure sensor on the dryer bottle to get the compressor to come on.

Can you jumper that connection and see what kind of high and low side pressures you are getting?

I fear you may have a giant leak and the R134 went right on through.

sgaar 04-27-2008 11:39 AM

If the system was taken apart to install the new components you will have to vacuum down the system before you can add new refrigerant. If you don’t do that then you will have a mixture of air and R134 and the system will not work. If you don’t have the ability to vacuum the system (very few non pros have) then get a pro to do it and fill it up. I will cost you about $200 but it is the only way to get it to work.

82gray380 04-27-2008 01:02 PM

As you have already surmised, I am not a AC pro at all, but I am always willing to try to figure it out. Is it possible to post a picture of the pressure sensor on the dryer bottle or at least a detailed description of the location, so I have an idea of were to use the jumper wire. I've tried the repair manual I have, but it has almost nothing about the AC unit. Thanks in advance.

ScottinSoCal 04-27-2008 02:09 PM


Originally Posted by 82gray380 (Post 1836929)
As you have already surmised, I am not a AC pro at all, but I am always willing to try to figure it out.

I think you may have missed the key point - your car's AC is NOT a "figure it out as you go along" job. If you didn't evacuate the system before you tried to charge it, running the compressor will damage it. If you opened the system and didn't replace a couple of key parts, running the compressor will cause more damage.

Don't jumper anything unless you have the equipment to completely evacuate the system. You can certainly add a can of refrigerant to an already working system that just happens to be a little low, but without the proper equipment you can't replace parts and expect to get things working by trial and error.

aam 04-27-2008 03:21 PM

Start from the beginning you have a r12 system.
You can not add r134 refrigerant period.
Now if you want to convert to r134.
You must replace the accumulator, drain most of the oil and measure it, replace it.
It will not mix with the r134a.
Replace may be the exp. valve.
And may be hoses, compressor etc. If not working.
Vacuum the system down ck for leaks and fill.
This is the minimum.
If you don't have the knowledge, and have the necessary tools stay away.
One more thing it is not legal to vent the a/c system.

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