87 300d turbo ac stops working when hot out - PeachParts Mercedes-Benz Forum

marketsync · #1 07-04-2007, 06:06 PM

I have 87 300d Turbo with about 280k miles on it. I am having a strange problem with the AC system. When ever it gets to be above 77 + degrees out side the AC cuts out and stops working. When the weather is in the 60’s and low 70’s it works just fine. However as soon as it starts to get hotter than 80 it stops working after about 20 mins of the car running. If I stop, turn the car off then restart it, it will work for a little while.

The compressor stops and it just blows humid air.

I haven’t had any other electrical problems with the car,
I have replaced the following items.

• Ac system has been evacuated and refilled 2x.
• New AC Relay Unit
• All Electrical Fuses have been replaced
• The push button unit was replaced with a new one last summer

I sense it is something electrical because the only changing factor is the temp outside.

Any thoughts?

sixto · #2 07-04-2007, 06:20 PM

http://www.peachparts.com/shopforum/showpost.php?p=1546012&postcount=70

The last newbie I offered a link to read me the riot act. Let's hope you're more tolerant.

Sixto
87 300D

Brian Carlton · #3 07-04-2007, 07:20 PM

Quote:

Originally Posted by sixto

http://www.peachparts.com/shopforum/showpost.php?p=1546012&postcount=70

The last newbie I offered a link to read me the riot act. Let's hope you're more tolerant.

Sixto
87 300D

What the hell are you offering a long and drawn out procedure like that for?

Do you know how long it's going to take to go through all that nonsense..........??

WINGAS · #4 07-05-2007, 07:27 AM

Mine does the same. Rather than spend a 8 hour day running through those test in teh link, I sim-ply keep the temp control at 75 or so, never at "full cool". It still cools, and doesnt cut out. Also ahve to keep the rpms down ( no Italian tuneups),. I beleive the high side of the system is seeing too much pressure when its hot out and we have the controls set to full cool ( below 68 or so). That will cause the high side pressure switch to open. No A/C.

NC Benz · #5 07-05-2007, 08:35 AM

What are you running for refrigerant?

Quote:

Originally Posted by marketsync

I have 87 300d Turbo with about 280k miles on it. I am having a strange problem with the AC system. When ever it gets to be above 77 + degrees out side the AC cuts out and stops working. When the weather is in the 60’s and low 70’s it works just fine. However as soon as it starts to get hotter than 80 it stops working after about 20 mins of the car running. If I stop, turn the car off then restart it, it will work for a little while.

The compressor stops and it just blows humid air.

I haven’t had any other electrical problems with the car,
I have replaced the following items.

• Ac system has been evacuated and refilled 2x.
• New AC Relay Unit
• All Electrical Fuses have been replaced
• The push button unit was replaced with a new one last summer

I sense it is something electrical because the only changing factor is the temp outside.

Any thoughts?

Brian Carlton · #6 07-05-2007, 08:50 PM

Quote:

Originally Posted by WINGAS

Mine does the same. Rather than spend a 8 hour day running through those test in teh link, I sim-ply keep the temp control at 75 or so, never at "full cool". It still cools, and doesnt cut out. Also ahve to keep the rpms down ( no Italian tuneups),. I beleive the high side of the system is seeing too much pressure when its hot out and we have the controls set to full cool ( below 68 or so). That will cause the high side pressure switch to open. No A/C.

You can easily verify if your suspicion is correct. Just jump the pressure switch and drive it...........the switch cannot open and kill the compressor. The only reason the pressure switch should open is if the aux. fan is not working.........or.......it's defective.