Where is the low side freon port on a 1997 grand marquis?

Look on the passenger side of the engine near the strut tower. It will be on a large aluminum line.

there are 2 sizes,
there are only 2 Freon lines, one big and one small.
am I to guess that you cant just look at them and follow them>?
the tool (gauge) has only one size fitting and only fits the correct low side fitting, so if you looked you'd have seen it.
hint, its in the engine bay.
the loop starts at the fire wall to compressor then condensor and back to the fire wall.
read page 9 , HVAC , chapter ,under ZJ
all you need to do on any ca,r is look, longer than 1 second.

The freon pressure will read close to air temp when the compressor is not running. On both high and low sides.
You may have to check the circuit for power to the clutch. It could be a pressure switch, the ac clutch, or a relay.

the low side has the larger tubing the ports are different sizes the tool will not fit on the wrong one

the low side has the larger tubes and the ports are different sizes so you can't put it on the wrong port

Follow the a/c lines, from the condenser in front of the radiator, until you find one or both of the hose connections and the one that the a/c recharge hose fits onto is the low side port. The recharge hose will not fit the high side port.

The Low Pressure Port is where you want to charge. It should have a blue cap. Here is a picture of the Low Pressure Port:



I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

You should find a fill stem on the black oblong tank or right next to it. This is the low pressure side. You should get a Vacuum pump which can be loaned from Autozone or Oreillys with a refundable deposit. You need to draw out the moisture in the system and create a Vacuum before you refill it.

You should also use an Oil charge for the compressor. There are Freon cans with the oil charge already in them. However, there are different weights of oil used in the compressor. Let the Auto parts people get you the right type for your car. There are different weights, just like engine oil has different weights.

You will need to jump the connector at the low pressure switch to get the system to take freon. Once you have enough to close the low pressure switch you can remove the jumper wire and fill at will.

mcdevito75 here, The low side port of your A/C is located on one of the shiny metal lines comeing out of the firewall, they are attached to the evaporator under the dash, from the firewall carefully follow these silver lines till you reach the charge port. The port may be covered with a brass looking cap, un srew the capp and the port looks like the valve on the tire.

Add a can of freon. Low side should be about 35