I just flushed the system, changed the evaporator and all seals. holds vac but doesn't seem to want to take the refrigerant into the system. could I be using the high side in front by the coils. any suggestions

the one you can access from the top is where you fill. where the bar crosses over the engine

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the port just in front of the brake booster? Could I have not pulled enough vacumme. I pulled vac for 15 min to -10 and it held. I can remember a can emptying in minutes in the past.Should the compressor be engaged. It isn't rotating. could that be because there isn't enough refrigerant

The port is in front of the engine, up top near the valve cover. That is the low side. That is where you pull the vacuum and then fill with freon. I hope you added 6-8 oz of oil. The high side is on the passenger side of the engine. You use this only to get a pressure reading.

If you pulled vaccum on near the brake booser, which line did you connect it to? I hope it was not the brake booster line.

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if you hook into the high side when you charge it your can will explode as it reaches 300-500psi. I think low side is like 90-150 not sure though

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1981 300SD 512k OM603

on my 85 300sd turbo 126 there are 2 ports one all the way to the front right at the condenser. then there is a second port that runs just in front of the brake booster. I pulled a vac by the front port at the condenser coils. I added 8 oz of oil. 4 .oz in the dryer and 4 to the compressor.

Some body knows where the High side is on this car. and where to pull a vac and where to fill from. Help! Ray M

The lines do not cross over the engine. They are all on the drivers side.

The line that runs from the compressor to the condensor and receiver/drier is the high pressure line. The low pressure line should be of much larger diameter and runs from the evaporator to the compressor.

You need to pull a vacuum of close to 29" Hg for several hours. Pull the vacuum and fill from the low pressure port. The compressor will not engage until there is about 10 psi in the system. You will need to jumper the low pressure cut-out switch to make it engage sooner than that.

Thanks tangofox I was hopeing you or some of the other knowlegables wwould show up

... if you have the system in a vacuum, you should be charging it with liquid with the car off into the high side so as not to flush the oil out of the compressor.
then after the pressure equalizes with the rest of the system, use gas to finish off the rest of the charge with the system running.
it's best if you have the correct amount of refrigerant in one bottle, so you don't have to switch cans during the charge.
it is very difficult to charge a system from vacuum with cans... air is almost assured to get into the system compromising the charge.

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I cant seem to get the compressor to kick in without jumping the compressor. Low side is 150, high side is 152. Charging at the low side with 134a cans and both hoses connected to my gagues. Does any one think it could be the pressure switch or aux fan switch. Someone in another post mentioned a KLIMA. I saw one in my fuse box. This is Greak to an old 123 vet. I've never heard of one. can any of these be ruled out with a simple continuity test with my ohm/volt meter. RAY M

You can eliminate the low pressure switch by unplugging the wires and jumpering them together. The aux fan switch has no connection to the operation of the compressor.

A low side pressure of 150 suggests a problem.

I jumping the wires didn't do a thing. Should I have changed that out along with the new dryer & expansion valve. What does the low side pressure seem to indicate. Thanks tango fox

A problem with the compressor or expansion valve. Those pressure readings were with the compressor engaged, right?

Probably an ACC issue, but swapping the aux fan and compressor relays might be worthwhile, just in case the relay is the culprit.

New expansion valve. could a misaligned or missplaced washer in the expansion valve be clogging the new valve. Could the compressor be bad if it engages when jumped. Thanks RAY M

what is a ACC issue

reading was when I was jumping the compressot for a short period