I just fix my ac in my 1986 Lincoln Town Car and charged it .i place the low pressure gauge to check my pull down and at temperature of around 84 degrees my low side give me a reading of 45psi is this good or what should the low side be at this temp?Should it be around 50 or better? I don't know for sure, I am using 134a in the system.Please give me and idea of what the pressure should be if the system is fully charged?

get the right gas to use and charge it to suction and pressure pressures on gauges
if you need to charge it , fix the leak first
better still get a professional ac specialist shop to do the job properly

If the compressor wOnt cycle, it means that the pressure is not correct. How much freon, (and what type) did you put in, and did you PULL DOWN (with vacuum) the system to about -29 inches before putting the freon in? Did you use manifold gauges? If so, what is the high pressure, and what is the low pressure, at what ambient temperature?

According to AutoZone, 160 degrees F.
http://www.autozone.com/autozone/parts/1986-Lincoln-Town-Car/Thermostat/_/N-ij97xZ9pd73

YOU NEED A R-134 GAUGE SET TO CHECK LOW PRESSURE SIDE AND HIGH PRESSURE SIDE.YOU ALSO CAN BUY A LITTLE CHEAPER GAUGE TO CHECK YOUR AC LOW BLUE SIDE AND HIGH RED SIDE AT ANY AUTO ZONE OR ADVANCE AUTO PARTS.WHAT YOU DO WHEN YOU GET YOUR GAUGE SET HOOK GAUGE TO LOW PRESSURE SIDE BLUE CAP PORT AND GAUGE TO HIGH SIDE PRESSURE RED CAP PORT.YOU CRANK CAR UP GET IT OPERATING TEMPERATURE.THEN TURN AC ON HIGH COOL LET RUN 3 TO 4 MINUTES.CHECK LOW SIDE GAUGE READING SHOULD BE 28 - 32 PSI. HIGH PRESSURE SIDE GAUGE SHOULD 199 - 228 PSI. THATS NORMAL CHARGE. SEE YOU CANT JUST RECHARGE AC SYSTEM UNTIL YOU CHECK IT FIRST YOU WILL DAMAGE SYSTEM .NOW YOU CAN GO TO AUTO ZONE PARTS BUY A CHARGE CAN WITH GAUGE AND HOSE.ATTACH TO IT.YOU NEED MORE THAN ONE CAN.WARNING MAKE COMPRESSOR IS RUNNING WHEN YOU TURN ON AC .BECAUSE IF COMPRESSOR NOT RUNNING CHECK FUSE AND AC COMPRESSOR RELAY.IF BOTH OKAY.YOU COULD HAVE OPEN CLUTCH COIL A FAULTY LOW PRESSURE SWITCH WILL CAUSE AC NOT TO WORK. IF LOW PRESSURE GAUGE BLUE SIDE PRESSURE IS 28 OR 30 YOU DONT NEED A CHARGE.PROBLEM SOME WHERE ELSE.BE SURE TO WEAR SAFETY GLASSES WHEN WORKING ON AC SYSTEM.

You have a bare wire short some where. Look around the alternator and starter. Also look and smell for smoke or burn rubber smell.

The oil pressure switch is a short circuit when there is low oil pressure. Removing the wire from it should turn off the warning light. If it doesn't, the chances are there is a short circuit between the lamp and the sensor.

In order to charge, you must locate the low pressure valve to install the refrigerant. The low pressure valve is between the compressor and the evaporator. Do not charge on the High Pressure side, The high pressure valve is between the compressor and the condenser. To locate the low pressure valve, follow the line that comes from the compressor and routes toward the firewall. The valve will be somewhere on that line. Do not overcharge. The amount of pressure that is needed on the low pressure side will depend on the ambient outside temperature.

whenever the ac system has been opened it should be hooked up to a vacuum pump designed to evacuate the ac system of any foreign debris and oil etc and after should be able to hold a vacuum to show that there are in fact no leaks then if all is ok at this point you can then charge your ac with the proper freon specified for you car when the pressure reaches satisfactory level the ac compressor will then cycle on you should not bypass the low pressure switch

Found the fix on another forum - replace the AC clutch relay in the power distribution box under the hood.

This has worked for at least two people with this exact problem so far.