Polo35m

Hey guys I've gotten myself into a bit of a pickle. I replaced my radiator this weekend which required discharging the AC system and removing the evaporator as well.....Not an easy job. Anyway I have everything put back together, evacuated the AC system, recharged it slowly with a static amount of r134a but cannot get the compressor to come on. I've never had this problem with any of my other Mercedes....athough they were older models. The indicator on the air conditioning cluster reads "AC OFF" and when you go in the menu screen to try to turn it on, it reverts right back to off. Any help would be greatly appreciated.

dlafever

• Firstly, the evaporator is in the air handler box under the dash, I believe you are talking about the condenser, yes?
• Did you plug the electric fan back in? Without airflow across the condenser, the heat transfer will not be sufficient and it will prevent the Climate control from functioning (disabled due to fan failure.)
• Hoping you have a set of manifold gauges connected so you can see what the high/low side pressures are doing -- not the actual values per se, just how they are behaving relative to each other.

I recently replaced the compressor on my S550 and found that I was able to get the require 1180g of R134a into the system without issue. BTW, the compressor in these cars runs all the time but pressure is regulated by an electrically operated valve.

Also would be helpful if you could fill out your user profile so we know what mode/year/location when we're talking about your car.

Polo35m

Thanks for the reply. Sorry, I did mean the condenser. Yes, new to this forum, but I did put 2008 S550 in the title. I will check the fan plug again, but I'm certain it is plugged in correctly. Yes I have a vac pump, gauges and a 30lb cylinder of r134a. Been doing most all my own service work on these cars for nearly 35 years and have never had an issue like this. I called my connection at the dealer and he told me it has to come to the shop and be reset....no other way around it. I just can' believe It! I have 2 vintage Ferraris, this S550, Wife has BMW 535i, Son has BMW 325i, daughter has ML 320...I have done significant ac work on all of them with my eyes closed and have never had this type of problem. I guess it's off to the dealer tomorrow. Will post what they do. Appreciate the help.....I will check that plug tomorrow morning however.

dlafever

Well from a fellow gearhead (30+ years as well) it is sometimes the simplest thing that would prevent an otherwise flawless repair from being a reality.

I figured out the fan connector trick on my recent compressor replacement. Having known that others needed to connect to the Star Diagnostics following A/C repair to get things working again, that's what I did. Only to find that Star wanted me to reconnect the connection to the fan. Oddly enough I didn't need to 'reset' anything, just identify the fan was unplugged and plug it in. Once I did that it sucked in refrigerant like my beagles clean the floor of the kitchen!

If you're in the S550 for a while, investing in the Star system is well worth the money.

You wouldn't have the photos of the Ferrari's to share would you?! Always great to see amazing cars.

Good luck sorting it out!

Glen Mosley

I had the same issue, I changed a leaking hose with one from the dealer, charge the system yet the air conditioning would not function until a snap on computer was able to go into the air conditioning system and erase the fault codes that said ow refrigerant. After that on the dashboard the AC off was toggled on and the compressor and fan kicked on. A bit of more information 2 lb and 4 oz was pressurized in the system from the high side, red hose

Kalakov222

Hello everyone, I am intending to doing a deep dive into this, saving me from potential ripoffs. Hope everyone can relate to the feeling and help me with the following.
1. How much volume of R134a would my system take.
2. Can anyone provide schematics of the AC System (w/s Manual).
3. Where do leaks usually occur.
4. How to detect leaks in the system.
5. How to stop leaks in the system.
Thanking everyone for any input.

BOTUS

its on a label on the car under the bonnet - depends if you have rear AC or not

its around 900g without rear ac and 1300g with rear ac
the condenser rots out - under the bonnet, look with a torch - around the edges for dark / dirty / dusty / oily areas if u see it, its gone
the law says must empty and recover the gas, pull a vacuum for 10 mins and if Ok can refill
you stop leaks by regularly using the car, 20 mins AC use every 2 weeks as a bare minimum - more = better -
NEVER turn off AC ever (its just like a domestic fridge at home) constant use will last 30 years (except cars get salt over the aluminium condenser and flexi-hoses to leak - so its not going to do 30 without a service now and then)

Kalakov222

BOTUS: Thank you for the advise.