Mike4l

Good day, I have a very weird and sad problem with my ac and I have to try to get it fixed before Sunday, problem started after changing my engine, my ac stopped working, I was told it was the compressor, thought this hot Texas summer I changed my compressor 3 times, come to later find out I had a leak in my condenser, I had to change that my self because I didnt want to waste any more money than I already have, when I changed it everything went well, I had no more leaks and my system help the Freon well, I plugged in the ac pressure switch which was tested and had electricity present in it but my ecu still reads that I have no pressure, I did a little research and found out the ecu won’t turn on the compressor until it reads that it has pressure which it does because I used a Freon system to check, please help if there is any way I can bypass this please it’s hot as hell and I have 2 more days before I go to my college campus.

Odd Piggy

What engine do you have? I think you have a W203 C230 and this is the W204 forum.

Mike4l

it’s a c230 with a c350 engine in it, 3.5L v6

Odd Piggy

Okay, so a W204 engine. Others have jumped the contacts on the switch to bypass it. I don’t have the car anymore to check, but can you disconnect the pressure switch connector and jump/short the 2 contacts on the connector? It should be attached to the bottom of the condenser on the drivers side of the car.

Mike4l

ok thank you so much I’ll try that and let you know how that works, just to make sure you know, there is electricity registered when I tested it, it’s just indicating I don’t have pressure on my ecu

Odd Piggy

12 volts? I think the pressure switch makes or breaks the circuit to the compressor clutch. If 5 volts it may not work exactly the way I remember. I can’t get to my W204 wiring diagrams.

Mike4l

no luck found, do you think the ambient air temp sensor might be a problem?

Odd Piggy

I think the ambient air temp sensor inputs to the hvac system only where the outside temp is too low and turns off the compressor around 28F to avoid cycling liquid. Is yours bad?

Mike4l

“yes I have the 185f on the dash”

Odd Piggy

I don’t know what a temp like that will do to the HVAC system, but I would think nothing on the AC side.

You’re running out of time and about to have a hot trip back to school. Let’s go back to basics. Check all fuses, specifically fuses 12 & 22 under the hood. Here’s a listing I found online:

https://fuse-box.info/mercedes-benz/...uses-and-relay

Do you have a scanner? You changed an engine, so I thought maybe you would. That may help pinpoint the failure. A simple code reader may not see HVAC codes. And I’m not sure if a compressor clutch failure sets a code.

Good luck.