87 300TDT - Air Conditioning in Las Vegas - PeachParts Mercedes-Benz Forum

1987-300TD · #1 07-18-2012, 06:06 PM

Happy Wednesday! I was troubleshooting my air conditioning over the last several weeks. I am not an AC expert by any stretch. :-)

Symptoms:
* (Outside temp = stupid hot > 100) With the AC on and blowing on high, the compressor does not engage. I get hot air coming out of my center vent. The driver and passenger vents do not appear to be working properly as they were not blowing anything.

* (Outside temp = hot > 85) With the AC on and blowing on high, the compressor kicked on and blew cold air through the center vent.

* I worked some with an AC mechanic. Unfortunately, most of his experience was fixing bus air conditioners. When he jumpered the 2 wires connected to the cylinder in the attached picture, the compressor kicked in and blew cold air. I did not have a proper jumper over the weekend so I could not recreate the scenario.

Does this sound as though this cylinder thing is toast? If so, what is it called? Is it something I can comfortably replace? :-)

Again, Thank You to Everyone for sharing your knowledge!

TIA,
glenn

vstech · #2 07-18-2012, 07:21 PM

it sounds to me like you need a new pressure switch... the cylinder thing is the reciever, and the pressure switch is in the refrigerant circuit, so replacing it, means dumping the freon...
if the system is working with it jumpered, the system is not flat. I'd go ahead and leave it jumpered and just keep an eye on the system charge. if it goes low, have the charge removed, and replace the switch.

1987-300TD · #3 07-18-2012, 11:38 PM

Thank You for the reply VSTech! Another question: Can I damage the system more by running with the system jumpered in this manner?

Also, I have another post with a miscellaneous wire hanging. I believe it to be a ground of some sort but I do not know where it belongs. Would you mind taking a peak to see if it is related to the AC? http://www.peachparts.com/shopforum/diesel-discussion/321639-87-300tdt-hydraulic-reservoir-foot-miscellaneous-wire.html

Thank You Very Much for sharing your knowledge!!!

glenn

Air&Road · #4 07-19-2012, 07:51 AM

Yes you can, but that is why VS told you to keep an eye on it. The purpose of that switch is to disengage the compressor in the event of a very low charge. Continuing to run the compressor with a low charge will damage it due to the fact that when no refrigerant circulates, no lubricant circulates either.

Hope this helps.

1987-300TD · #5 07-20-2012, 01:02 PM

Thank You for your replies! One last question, how do I "keep an eye on it"? Is there a gauge or some other way to check the charge of the system?

(Sorry for the newbie question.)

Thank You!!!

glenn

vstech · #6 07-20-2012, 02:42 PM

just keep a constant note of it's function. I.E. if the air is cold, it's still ok, if not, remove the jumper, and have it serviced!!! DO NOT DRIVE WITH THE AC ON IF IT"S NOT COOLING!!! if the switch is bypassed, you will quickly burn up the compressor!

1987-300TD · #7 07-20-2012, 07:09 PM

Thank You Very Much for sharing your insight!!! I am going to play with this over the weekend. I will let you know how it works.

TIA,
glenn

1987-300TD · #8 07-24-2012, 03:02 AM

Good Day All! I jumpered the 2 wires in this post (I will post pictures later.). However, no cold air. I do not believe that the compressor kicked in at all. To that end, I am back to square one in my troubleshooting procedure.

I removed the "tire cap" from the system and depressed the valve. I have pressure in the system.

Any clue as to why the compressor will kick in when the outside temperature is 85 degrees or less?

Thank You for your knowledge and patience!!!

glenn