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Discussion Starter #1
Hello everyone.
After nearly a year with no problems the Benz has started again lol.
I had to replace the Gear selector about a month ago. luckily I found 2 at the salvage yard for 18 bucks. got it changed with no issue.
Cars been fine since... Until yesterday. Yesterday morning on my way to work my ac started blowing warm. I assumed it was probably a low charge.
I knew I had some refrigerant at home so I decided to just wait until I got off to check it.
On my way home I noticed the car seemed quieter before I knew it I had a CEL come on. As soon as I pulled in I popped the hood. First thing I noticed was the fan was not running.
I knew why my AC wasn't working.
I turned the AC on high, turned on Auto... Nothing
Its odd to me that it just stopped working out of nowhere.
The car didn't run hot the temperature has stayed normal.
I saw some posts that discussed this issue but none that I read had the CEL and most said their fans were running wide open or very slow.
I plan to pull the codes today and post. just wanted to see if anyone had any ideas as to where I should start.
 

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Discussion Starter #2 (Edited)
Update... Mega Pre Fuse 125 amp is good. Getting 12V to the fan connector. CEL turned out to be a vacuum hose I knocked lose yesterday. Looking like its the fan to me.
Can I put 12V directly to the fan to check operation?
Am I missing something else?

Thanks
Brad
 

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Got a C240 and had a similar issue. If your harness is like mine, you have 4 wires to the Fan clutch. 2 fat ones (brown and red) and 2 small. The brown is the ground and the red constant +ve. The others get 12v when the key is on and the last one gets variable voltage from the PWM. If an issue like no freon, PWM wont send voltage to fan.It also adjusts speed based on water temp sensor.

Anyway you want to jump the 2 12volts onto a constant 12 v source , ground the brown and then take a lead and tap the 3rd connection for like 3-6 secs. If it spins, the fan is working. BEWARE dont leave this 12v on for long or it will damage it. The unit is desgined to get a variable voltage from 0-6 volts and leaving it on 12v is not good.

Good luck
 

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Discussion Starter #4
Well the fan is working. I checked with test leads and checked by unplugging the temperature sensor. Also left the car idling for a while and the fan came on.
I put gauges on the car. Low side is around 45/50 psi High side is only 50 psi.
I’m no HVAC pro but since the high side pressure is so low I suspect the compressor isn’t working either because of a bad pressure switch or a bad compressor.

Any thoughts before I take it to the shop?
 
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