Hello, I’m experiencing some issues with my blower fan & A/C Button flashing 3 times when pressed. A/C Button light does not stay on and does not blow cold air. I’ve also been noticing that the blower fan only seems to work somewhat as in when turned on it will not always work immediately and randomly start functioning again. I’ve now tried diagnosing the problem by checking the low pressure A/C valve. My gauge that was from A/C Pro read 87 psi. This is where I’m not sure how to solve the overcharging. How do I diagnose and fix this problem?

2009 Mercedes Benz C300 4 Matic

Thanks

 

So many questions. 87psi on a fix-in-a-can? What was the ambient? Was the car running? How do you know it’s overcharged?

 

Yes it was an A/C Pro can pressure gauge that I used with the car on and the blower fan on max cool without A/C running, A/C button won’t stay on when pressed, it will flash 3 times which might be indicating something I’m not aware of. I’m not sure if the outside temperature has anything to do with this. How do I know if it’s overcharging, well based on the pressure gauge reading it’s above the full limit of free on and also that the blower fan somewhat works, maybe it’s going into a safety mode because of the high psi pressure.

 

Today, the blower fan has been working fine as soon as I start up the car multiple times throughout the day but isn’t guaranteed after these malfunctions. A/C button flashes 3 times when pressed, id like to figure out what it’s indicating, seems like it’s in need of something to work. After doing research, it’s seems like the common issue is that it’s low on free on but mine is more advanced to figure out.

Does it have to be hooked up to shop equipment to reset or diagnose?

 

Yes, it needs a proper scanner to read codes, not a generic OBD2 read like autozone

 

I’ve been wanting to get a better one, maybe something like this.


Autel MaxiCheck Maxicom OBD2 Diagnostic Scanner MX808(Advanced MD808 Pro Same MK808) With 5ft Extension Cable Full Systems And Service Functions Oil Reset EPB BMS SAS DPF TPMS Relearn IMMO

 

Ambient temperatures have everything to do with AC pressures. Only way you get away from that is if you're filling by weight, aka an evac and recharge. Without that, you're in guesswork territory.

Regarding overfilling, can you explain how you got to this point in the first place? Did you fill the system before you encountered issues? If not, and all you're doing is trusting the pressure gauge on the can, I'd scrap that diagnosis and start again. Better yet, pay for the $90 evac and recharge so you have a good baseline, then go from there.

 

Once I get my new diagnostic scanner delivered with full system diagnostics, hopefully I’ll be able to figure out what this could be with a more precise answer other than knowing that it’s appearing to be overcharged. I will explain when I look more into it.