1997 will be running 134a "Freon"
Compressor power(12volts) comes from AC switch in the cab, but it runs through 2 pressure switches on its way to the compressor.
Both switches need to be closed for the power to pass thru to the compressor.
Basically one switch is a low pressure switch so compressor won't run "dry", and the other is a high pressure switch so compressor won't blow out seals/lines.
Could be pressure is too high so when compressor comes on and adds pressure the high pressure switch opens and power to compressor is cut off, when pressure drops again switch closes and compressor comes back on, so just cycles on and off.
Use a volt meter or test light on compressor to see if power is indeed being cut, because it could also be that the field coil on the compressor pulley is out of adjustment, not an uncommon problem on Fords.
But if power is going on and off field coil is fine.
If the system has been left off for a few years then accumulator/drier will need to be replaced, not an expensive part but system does need to be drained and then recharged.
Google: DIY automotive AC service
They are all the same, AC is AC, you will need some gauges to test pressures, these can be rented.
Because it is not blowing cold in the cab the expansion valve or evaporator may be bad/clogged.
Or it could be the Blend Door, Google: Ranger Blend door
AC can be a money waster for DIY, 134a ain't cheap, lol.
Some independent shops that do AC will test the system for you for a set price, let you know what needs to be changed and if there are any leaks, then you can change the parts and fix the leaks yourself.
This can be cheaper than replacing things on spec and hoping for the best.
The way AC works is pretty simple.
When you compress anything it gets hotter, like air, air compressors get hot and air in the tank gets warm, then when you release that pressure, decompress it, it cools down, air feels cold coming out, it is releasing the heat added by compressing it.
"freon" is a gas at room temp but a liquid when under pressure, so if there is a leak there will be no residue at the leak point, pressure in the system just drops.
Freon holds and releases heat very well.
So the compressor heats up the freon, it then goes to the condenser(in front of radiator) to cool it down a bit, it then goes to Accumulator/drier, hot freon storage tank and it removes moisture from compressing it.
From there is goes to the expansion valve, this decompresses the freon so it gets very cold, this cold freon goes thru the evaporator, like a heater core but for cold instead of hot.
Then freon goes back to compressor.
Compressor-------condenser-------- Accumulator/drier------expansion valve-------evaporator--------(compressor)
Last edited by RonD; 07-16-2016 at 11:12 AM.