mrobinso

A really quick, cheap, and easy DIY to make sure your AC is nice and cold for the upcoming hot summer months. If your AC is already pretty cool (like mine) but on really hot days you find it takes a while for your AC to really get cold, you might be a good candidate for this DIY. Only a few simple steps:

1) Purchase 14 to 18 ounces of R134a refrigerant. You will want to make sure you purchase a can with a gauge readout if you have never done this before and don't already have gauge. I went with this one from Interdynamics (18oz) at Advance Auto Parts ($22.99 after discount): http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_R-134a-EZ-Chill-Refrigerant-plus-Oil-%2818-oz-%29-Interdynamics_7010015-P_N3571B_T|GRP2004A_____ You can purchase it online (used coupon code A123 at checkout for $10) and pick it up at your local store.

2) Read the directions and read the level of the ambient temperature on your information display immediately before commencing recharge and make a note of where on the gauge it indicates correct PSI should be.

3) Pop the hood. To the right of the engine towards the back there is the low-end valve for the C55's refrigerant line. You will note a small pipe (1/2" thick) with a valve and black cap. That is your low-end valve. Unscrew the cap and store.

4) Firmly screw the connector of the gauge and hose to the bottle of refrigerant (this is very self explanatory).

5) Start the engine and turn the AC to level 6 (recommend not putting it on AUTO) and the cold knobs all the way to the left. Let the engine run for 2-3 minutes.

6) I recommend wearing gloves and eyegear for this part (although there was no back spray from the canister if you want to chance it). Pull back the plastic sheath from the end of the hose and firmly press the connector down onto the low-end valve. Pop open the cap cover and squeeze down on the cap until the gauge reads a desired PSI. When I started my PSI was in the blue at 27 PSI and when I finished the gauge said 37 PSI (this was at a 78 degree ambient temp.). It takes a little elbow grease to hold down the cap so the gloves help with this.

7) Remove connector from low-end valve but firmly grasping the connector and quickly pulling up. If your not wearing goggles, there is little chance of back spray but look away as you pull up just to be safe. Check AC inside cabin for coolness (should be chilly!). Check the gauge one more time on the low-end valve for a back-up reading. Top-up if necessary. Firmly rescrew the black cap onto the low-end valve.

8) You're done!

There was documentation on this topic on the forums, but figured I would share my experience in a fast and easy DIY for fellow C55 owners.

xxaarraa

Good tip Robinso. I used to fill up each summer on my old pickup truck, might as well fill the merc too this year. Though, it's important to not overfill.

Dingleberry

Do you understand that this is a completely closed loop system? Refrigerant doesn't get consumed nor does it "go bad". If you're having to top off your system each summer, that means that there's a leak somewhere...

xxaarraa

I was waiting for someone to pop up with the "textbook" answer. Yes, I do know it's a closed loop system. I also know that 99% of closed loop systems will start losing refrigerant once they start aging. It's a lot cheaper to spend 30 bucks to refill each year than go hunting for a slow, multi-year leak in the system.

mikekuriger

If you have a leaky AC in a car that's less than 15 years old, then something is probably damaged. I would highly recommend that you NOT add freon to an AC unit without proper training and gauges since it's extremely easy to overfill and destroy the AC in the process.

Also, it's very EASY to detect leaks. O-rings are cheap as well.

mrobinso

My AC system's pressure was at an acceptable 27 PSI (in the blue) prior to beginning the recharge and my AC was very cold before. If there is a leak (which I don't believe there is) it would be an extremely slow (as mentioned by xxaarraa) leak. Regardless, I am not worried about that at this point in time.

mrobinso

Are you making a general statement here or directing this at me? If directed at me, how did we go from a post about a simple charge up of the refrigerant (that was previously blowing cold air anyways) to suggesting that there is critical leak my car's refrigerant system?

mikekuriger

Because charging the AC system is not a simple task that should be done by the average person. There is never a need to charge an AC system that is not leaking.

mrobinso

Can you provide some supplementary back-up for this statement? Not saying your wrong, but simply from searching Google you will receive hundreds of hits regarding people "topping-off" or recharging their freon without problems.. Also, before and if you respond, I am not looking for a response stating that Google is not a valid or trustworthy research tool, I already understand not everything you read on the internet is true, just looking for where you are getting this information from.

xxaarraa

Mike, not trying to be a smartass, but the "average person" shouldn't be doing oil changes, diff fluid changes, mods, etc. etc. in the first place, which is what this site is all about.

Its amusing whenever someone on an enthusiast car forum says "this shouldn't be done by the average person"

thtguy

I read a great article about refrigerants the other day, and it is known in the technician world that R134a is prone to seep overtime worse than the older R12 refrigerant.

Technically my tires are a closed loop system but they too lose pressure. Anytime you have something pressurized that uses a soft seal (rubber or silicone) there will be some loss overtime.

Dingleberry

Comparing r134a (a haloalkane inert gas contained within a minimally expanding metal ) to tires (N2, O2, and water vapor contained within expanding rubber)

thtguy

Dingle,

you still have rubber seals that expand and contract. Oh! and schrader valves also! . so though they are as similar as apples and oranges you are still going to get some loss of gas over time. the difference is my Tires loose a few pounds a week or month. my A/C system loses a few pounds over 4+ years. And the sealing properties of R134a lubricants are documented as not being as good as that of an R12 system.

OT - Dingle why are you such a negative person, I just looked back through your recent posts, and it seems like more than 90% of them are some sort of disparaging comment.

Dingleberry

You fail to grasp the comprehension of simple gas laws, thermodynamics involving thermal expansion, and fluids. Your analogy is terrible.

Also this:
http://dictionary.reference.com/browse/lose
http://dictionary.reference.com/browse/loose

thtguy

I wholly agree to this comment if you own an older Audi. My wife's former Audi Cabriolet had no low side port. It is not a do-it-yourself system.

Dingleberry

Tell me how I managed to recharged the AC on my '94 S4 using a can of R134a and a hose?

Protip: You pull off the pressure switch and throw an adapter on the valve. Bam, low pressure port.

mrobinso

+1

Making constructive comments and critiques with a bit of heckling thrown in for good fun is one thing, but deliberately taking your time to put down someone for something they have done or said without any type of helpful or productive counterpoint is another and in my opinion is a waste of bandwidth here. I wouldn't usually comment on this but I have noticed the same consistency with the tone and themes of dingleberry's posts on this forum.

Dingleberry

Oh boohoo. Perhaps Mike and myself don't want others reading this thread thinking "OH HURRDURR MY AC ISN'T COOLING THAT GREAT, BETTER TOP THAT SUCKER OFF". No. Get the damn leak fixed, evacuate the system, and weigh in the proper charge. Do the job correctly instead of further polluting the atmosphere.

xxaarraa

Dear Dingleberry (who picked that username for you? I dont know what it means but it sounds like something I might want to use it to berate someone. "dont be such a dingleberry"),

Besides posting on EVERY For Sale thread about how its such a rip off or crapping on a thread where someone is merely offering a suggestion, you should do something more productive with your time. Like fixing your C32's radiator or something. Jussayin.

mikekuriger

I believe it's up to the individual whether they feel they are skilled enough to make a repair on their car. However, if you post instructions on how to do something and there is a risk of damaging it in the process, then it might be a good idea to at least warn the reader and suggest precautions to prevent damaging the system.

just trying to help!

thtguy

OK - sorry for my poor grammar not all of us are the scholar that you are are.

And you are correct that comparing tires to an A/C system was a bad analogy. The point I was trying to get across and still believe to be true is that there is expansion and contraction in an A/C system with openings (rubber seals and schrader valves) that can not and will never be 100% sealed (even 99.9% still has the potential to leak) and that gas does over time escape. should you have to recharge every year? No I don't believe you should, and if you do then you more than likely have a leak that could stand to be looked for. But if you have never charged your system and it is 5+ years old, it is likely that your system could use a little "topping up".

Dingleberry

1) I don't post in the classifieds
2) This thread isn't doing anyone a favor - It's, in fact, harmful.
3) I already have a Behr radiator

toddlaroche

Can someone tell me where the low-side port is on my 2002 E320? I'd like to top off the a/c system.

mkonei

There is nothing wrong with doing your own A/C work, if you are doing it correctly. This just isn't the correct way to do it. The systems are meant to hold x.xx lbs of refrigerant, not guessed at.

mrobinso

This post would be helpful if you could post the correct lbs.