Were do you put freon for ac and were are the high and low fitting located for charging ac 1991 audi 100

With the car running and the ac on high. Put the can fitting on to the low side of the ac line and open the can the Freon will be pulled into the sys and charge the unit. Most do it yourself kits will only fit on the low side of the ac. Hope this helps.

On a 2002 Mitsubishi Montero LTD, the a/c charging port is between the battery and the windshield. It is the port that has a cap labeled with an "L" (Low Side).

When the a/c is on, "L" (Low Side) gets cold while the "H" (High Side) gets hot.

Make sure you use the Low Side (cold) for adding Freon.

(note: over the counter freon kits should not fit the High Side port anyways)

To recharge A/C system in 2003 Frontier Crew Cab. Brother, don't concern yourself about the technical stuff of which is high or low pressure line. The refill/charge kit line will only fit on ONE of the 2 line fittings anyway. The line fittings I speak of are covered with a plastic cap like the one on your tire valve stem. Get your recharge kit from parts store, get mine from NAPA, with the line and a bottle of Freon. Find the charge fitting, usually on the passenger side under hood not far from firewall. Take the cap off and put it in your pocket. Open the kit, screw the piercing pin of the canister end out and put that end on the Freon canister. DON"T pierce the canister YET. Screw the other end on the charge fitting of your system and start the engine, turn on the AC on high, NOW pierce the canister top by screwing the knob/t-handle all the way in and then back it out half way. This will allow the Freon to escape the canister and the AC compressor will pull it into the system. Now, I've one trick for you. Before piercing the canister, get a small bucket of HOT water and have it there at the vehicle front. Soon as you pierce the canister and back the pin out half way, stick the canister into the hot water in the bucket. The heat will force ALL the Freon out of the canister till empty. Once empty, remove the kit line from the charge fitting on your vehicle, remove the canister from the kit line, trash the empty and hide the kit line where you can find it later, dump the water and put the bucket away, and go sit in the cool. One canister should take care of the recharge. If you put too much in from another full can, it may overcharge the system and still have no AC. That's just the nature of the beast. If it leaks down, get a leak detector kit from same place you got the recharge kit and find the leak. They also make a literal "Stop Leak" kit for AC systems too. Same place will have it. Brother, old school on this stuff. I figure things out quickly. There's no reason why this I told you won' work. It's what I do. Have fun Bro.

You put the freon on the low side, it may have a blue cap to let you know its the suction side.

its usually closer to a long round canister called the dryer or accumulator. when putting freon

make sure to run your ac on high while you are recharging the ac. good luck!

your vehicle came with R12 u can not purchase it , well depends on your STATE. but you will need to retro fit for R134A unless there is R12 still available at your area.

there are 2 locations a high side and low side most people use the low side connection to add freon.

100 AT PSI ON THE LOW SIDE TOO MUCH REFRIGERANT.LOW SIDE NEED TO BE 28 PSI. HIGH SIDE SHOULD BE 200 PSI.YOU NEED A MANIFOLD GAUGE SET TO SEE YOUR LOW AND HIGH PRESSURE SIDE.YOU PUT TOO MUCH REFRIGERANT IN AC SYSTEM IT WILL EXPLODE CAUSE SERIOUS INJURY AND DAMAGE THE COMPRESSOR.

On that year a4 and a6 there is no low side charging port. (sucks)
The way you charge those systems is by evacuating all of the refrigerant, then with the vehicle off, add the correct amount of refrigerant to the high side port (turning the compressor over by hand occasionally)

look at the ac compressor and follow the large ac line/hose untill u come to the service port,,has it been retofitted for 134a? if not go to parts store and ask for a retro fit foe the low side,u will need to remove the sharader valve before installing the low side retro fit,,also purchase a charge hose

follow the lines coming out of and into the compressor. The line leading from the firewall to the compressor is the low pressure line.
the line going from the compressor to the condenser located in front of the radiator is the high side.
Always charge with can in upright position through the low side line into the compressor.

Audi doesn't provide a low pressure charging port, they have a kit that the dealer must intsall to allow charging of the system