What should gage read when ac recharge is full on 2000 navigator

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Melvin, Recharging a cars A/C system. Check the attached links,instruction and guides, Good luck
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Right Wrong way to recharge AC
2003 Escalade charging AC
How To Recharge an AC System EricTheCarGuy
How to Properly Recharge Your AC System

I have done several myself with no problem. As long as the system is a newer one go to autozone or similar store and get a kit which comes with a gage and some freon. Make sure following directions exactly. Temperature must be 70 or higher set gage to outside temp hook to low side will only fit that side. Turn a/c on full charge no more than needed. Get a kit with dye in it that way if it looses freon the shop can pinpoint the leak

gauge in-tank probably your problems. You can test it at connector near fuel tank . there is 2 kind of gauge one is 0 to 90 ohms or 0 to 250 ohms. if the reading is not good then gauge is defect
hope it helps

Check to see if the compressor is coming on by turning on the AC while in park and listening for it. You should also see the RPMs drop a bit when it comes on.

If it is coming on then you just need to recharge the refrigerant. You can pick up a recharge kit from your local auto parts store. It'll cost you about 40-50 bucks. It should come with detailed instructions on how to recharge it, but basically you need to find the low pressure port, hook up the refrigerant bottle and charge it while the AC is running.

Let me know if you have any trouble.

2000 Olds Silhouette: plenty of gas in the tank but the gage will read full, 3/4 full, 1/2 full, and everywhere in between. Van runs fine. No other issues except the gage goes crazy and can't depend on what it says. ...

chances are that its just low on R134 refrigerant ... .. thats the new stuff that replaced freon (R12) years ago ... R134 is a smaller molicule so it leaks out much more easily ... in many cars it has to be topped off periodically ...there are kits available (with a gage) that will allow you to top off the R134 yourself if you are mecanically inclined ... if not then professional places can test for leaks and other problems and recharge your system.

No there is nothing you can do except go to the AirCon shop so the can drain and remove and refit new clutch assy as the rattle is the bearings worn out and needs replacing ,,and then it has to be recharged with freeon gas..
Have a doodday Ron

You didn't state what year the car was. If it's in the 90's or 2000's, It takes the R134A freon, not the 12A, and it should have been charged on the low side, not the high side.

Have you checked the refrigerant level,If it is low,No power will be supplied to the compressor.