Chedeng88

Yesterday, I took my C55 in because of A/C issues. It's just blowing luke warm air regardless if set to max cold or heat. I was also hearing a hissing sound at the center dashboard area when I turn on the A/C, so I had a hunch that I might be low on freon.

The tech confirmed my diagnosis and he vacuumed out and recharged the freon. We also found out that my battery was nearing the end of its life, so I had him replace it too.

Now I got my cold back, but I noticed that the heat would not really pick-up until I crank the thermostat all the way to the right (max at 80F?). Anywhere just before the max, I just get luke warm air.

The tech said he did all the necessary resets needed with regard to freon recharging and battery replacement. There were no fault codes too. I also mentioned to him the "defroster + recirculate button" reset, but he said he already did that via his computer which essentially does the same thing without having to press button combinations on the dash.

He's a little stumped right now and is trying to get in touch with some from MB Germany for some guidance.

Any ideas what could be the issue?

Chedeng88

UPDATE:

Tech said that it might be the climate control module itself (fishy how it went south around the same time the car was serviced). Anyway, if it truly is, I might just take this chance to upgrade to digital. Did a quick search and it seems a bit tricky to get the exact part that will work with the C55.

Anybody know the part no. this guy's selling in the thread below? Also, any closer and cheaper place to get it apart from NL?

https://mbworld.org/forums/mobile-el...ml#post4345951

Viper98912

I get this too sometimes and can't figure it out. I need to click it all the way hot then it starts hot, then I can back off and it stays in the hot range as normal. As long as I can "force" it to start, I haven't messed with it.

Chedeng88

At least you can back off with yours. With mine as soon as I back off from max heat, it becomes cold air.

Did it just start happening one day or do you know what caused it? Not sure if something went wrong during my freon charging and battery replacement.

Well anyway, I have until winter to figure this out or get a deal on a digital one.

Viper98912

Mine has been this way since I bought the car 4 years ago. It happens intermittently; honestly, I think it has to do with the outside ambient air temperature, and I don't think that the "auto" function is working correctly. Anytime I put it on Auto, the a/c comes on full blast when it shouldn't. Even though the Auto button is off, I think it isn't fully off and is messing with my manual settings.

I also have an odd problem where the a/c and fan will turn off completely, regardless of what setting I have it on. I don't think it's happened in over a year, but it used to happen every so often, just completely shuts off. It'd come back about 5 minutes later.

Careful on the digital swap; it isn't exactly plug and play; search the forum.

nancy1968zx

At least you can back off with yours. With mine as soon as I back off from max heat, it becomes cold air.

Chedeng88

I'll just wait until the weather gets cold again and test.

About the digital swap, I already did a lot a of searching. From what I gathered, the installation of the unit itself is plug and play. The real tricky part is getting one that will work with your car as appears to be hit and miss. A specific part number might work for another C55, but might not work with mine. Did I get that right?

Viper98912

i think so

Chedeng88

I think you're right on this one. It was around 50F this morning and lo and behold, I got heat even if I didn't set it to max.

The engineers at MB just don't want to give you 100% control of the car. Just like with the ESP off button, which we all know is not really 100% off.

pointman

Something like the "stepper motor". I think thats what its called.