Fryman182

At the end of last summer my AC went from blowing Air so cold I could pick a lock with my nipples to warm engine air. I said "Screw it, I will just worry about it when it starts getting warm again!"


And here we are now


I'm calling out to the Audi gods to come and assist me in my journey to find out what went wrong. Here is what I got down so far.

• No Codes other then a stupid radio amplifier which needs to be replaced.
• Low pressure side reading 35psi when off/on/up/down/left/right, etc lol.
• When I turn on the AC, I do notice a slight drop in RPMs
• VAG-COM claims the Compressor is on when I turn on AC ( http://www.ross-tech.com/vag-com/m_blocks/130-137.html Group 137 gives me On and AC HIGH)
• System was flushed and filled by local shop

I'm no AC guy by any means so at this point I'm stumped. It also helps a great deal that we have clutch-less compressors so I cant see if the thing is on or off with just my eye *****.


Any Ideas where to go from here what to try what to do?


2004 Audi A6 3.0 Quattro

georgeb944

Take it to a shop that knows what it's doing???

Fryman182

Welp, that one never would have crossed my mind.


The idea is to see if its something that I can do my self without spending hundreds of dollars.


Thanks for your words of wisdom.

georgeb944

You're welcome... After blowing up more than one AC system by my throwing Freon at it, I have decided that it's generally cheaper to have a pro do it than paying him to fix two problems, the one that was originally on it plus the one I added to it.

I guess that old age has its benefits.

SloopJohnB@mac.com

If the low side doesn't drop the compressor isn't.

jcman

Sloop is right if the reading does not move then it is a static reading "resting pressure", one way to tell would be the touch/feel test at the line entering the condenser "Hot to touch" and the suction line "Cold to touch".

What does the Duty Cycle and Result show in line 137 in Vagcom?

One problem with overcharging is that the evaporator will become flooded and log the accumulator causing liquid back to the compressor and this will ruin a Compressor because refrigerant compressors are only able to handle vapors not solid liquids and also cause a very high head pressure.

I am a 28yr Commercial refrigeration tech and small business owner in this field, auto AC systems are considered Medium/High Temp and basically all the same with exception to the metering devise be it TXV or Orifice Tube,
very primitive systems but still require the proper tools to service.

AR15Texan

You're gonna need to tell us the high-side as well as the low-side pressure. Why did the system need to be flushed and recharged? How many people have had their hands on it?

Meny

"Low pressure side reading 35psi" is the Key here

Your system is low on refrigerant and 35 psi in not enough pressure to trigger the pressure switch and clutch your compressor.

It's impossible to know how much more refrigerant is needed to fill your system because the gauge tells you the pressure, not the amount of refrigerant (see below for amounts).

You need to look for leaks in the system because your pressure is too low, so there must be a leak in some place, this is how I professionally service my A/C in all my cars with my home made kit:

You need:
- A/C manifold gauges for R-134a (You can get them on eBay for $30).
- Old or new refrigerator compressor.
- Soapy water in a sprayer (Dish wash soap works the best)
- Bright flashlight
- Eye protection
- R134a refrigerant with Pag 46 oil (See the amount of refrigerant you need for your C5 below). And remember not to overcharge your system --- THIS IS VERY BAD....
- I use a digital scale to measure the amount of Refrigerant going to my system from a bigger can of 1kg.


- Empty the system by recovering what is left of the refrigerant in your system.
- Pressurize the system to 250 - 300 psi from the discharge/high side, the wider one of the 2 (This pressure is the discharge side operating range) with the used refrigerator compressor (When on, one side blows air and the other produces vacuum so you will need to weld some threaded fitting so you can use an A/C manifold gauge set).
- Once you get to 250 - 300 psi, shut down the refrigerator compressor and close the discharge/high side in your gauge manifold.
- See if the pressure drops, if so, you have a leak so look for it with some soapy water. If you see bubbles, you found the leak.
- If it's on a fitting, change the O-ring and check for leaks again.
- If the leak is in a rubber hose, remove it and take it to a auto a/c repair shop and get it repaired (No need to buy a new one, I prefer to repair by replacing the rubber hose with a new one) And this will cost about $30 - 40 dlls. Check for leaks again.
- If the leak is in an aluminium line or condenser, remove it and take it to a radiator repair shop to get it welded. Install and check for leaks again.
- If the leak is the ac compressor, I can repair them by doing a rebuild but you can buy a new/used/rebuilt and replace it. Check for leaks again.

Once you are certain all the leaks are repaired (Pressurize the system and see if the pressure drops after 10 - 20 minutes).
Then, you may proceed to recharge your system after you let all the pressure/air out.

But first, you need to do a system vacuum (Remove the atmospheric pressure and moisture).
Remember the refrigerator compressor I mentioned?
Yes, this also works to do vacuum to your system......

Connect your suction/low side of the manifold gauge to the suction/low side port in your car (The discharge/high side is the wider diameter port and the suction/low side port is the narrower diameter one).
Open the suction/low side valve in your gauge manifold only, and power up the refrigerator compressor, connect the manifold hose to the port that does the vacuum in you refrigerator compressor and let it run for about 15 minutes.

After the 15 minutes have passed, you will notice that no air comes out of the other port in the refrigerator compressor (The port where air comes out when on and the same one used to pressurize the system to check for leaks).

Now you have vacuum and before turning off the refrigerator compressor, close the suction/low side on your gauge manifold, and then power off the refrigerant compressor.

System is ready to be charged with R134a refrigerant and depending on the size of your cans, you need to calculate what combination comes to the total needed for your C5 or measure the amount going in from a bigger can of 1kg with a digital scale:

A6 11.97 - 07.98 0.875kg of R134a.
A6 08.98 - 03.99 0.775kg of R134a.
A6 04.99 - 04.01 0.675kg of R134a.
A6 05.01 – 2004 0.575kg of R134a.

Once you have the cans of refrigerant, connect the can or tank to the suction/low side hose of your gauge manifold and purge the hose before opening the valve in your manifold. (With the valve closed, loosen the hose in the top before the manifold of your gauge to let the air out, and close it once refrigerant comes out).

Open the valve of your manifold suction/low side to let the refrigerant get to your system. If you are using 10oz size of refrigerant can (280gr) you will need 2 approx.

Turn on the engine and AC, verify thet the compressor clutch is engaged and connect the discharge/high side hose to the port in the car (PLEASE MAKE SURE THE HIGH SIDE MANIFOLD VALVE IS CLOSED, OTHERWISE THE CAN IN YOUR HAND MAY EXPLODE).

Monitor the pressure on both side once the system is fully charged. Remove the empty cans only after closing the suction/low side in the manifold.

Discharge side should be from 150 - 250 psi with all the fans on and Suction/low side should be from 30 - 40ish psi. Anything higher in the low side, means refrigerant overcharge or compressor failure.

Anything higher in high side, means refrigerant overcharge or fans not cooling the condenser properly.

I hope this helps and remember that this is for informational purposes only as I am not responsible for any damage caused to your system or God forbid, to your health....

Ask away....

jcman

However, when pulling a vacuum the proper tool to use is a Micron Meter to ensure the lowest inch mercury measurement is met of at least 50qmhg "microns" or 0.05 Torr less, I have manifold gauges ranging from $300 to $600 and no "Bourdon Tube" pressure gauge including mine will accurately show these very small vacuum measurements that are more then I can stress with the use of the "moisture sponge" PAG or POE oils.