will the compressor engage if the system is completely out of freon?

that was my suspicion. thanks for confirming!

Take it to an ac tech. They can do a vacuum test on your system to find the leak. If leak cannot be found they will re charge the system with freon and dye. If compressor then comes on and works you are good to go. When it does leak down again you will be able to see the dye and repair it yourself before having to have it filled again. If compressor does not come on they will re claim thier freon and charge you little or nothing for doing the check. That is unless you ask them to trouble shoot and fix the problem. My local ac tech only charges $50 for the vacuum check and full freon charge. And he charges nothing if it won't come on.

With some older vehicles the leak may be so small that it will take months for it to leak down enough that the compressor will not come on.

Freon does not just "come out" unless there is a leak. My '96 explorer a/c is going strong without ever being serviced. I believe my 99 explorer holds a about a pound of freon/refrigerant. Which is one can plus a little. If your system is low on refrig it means there is air in the system, meaning once the leak is fixed, a vacuum must be pulled to remove all air and moisture before injecting fresh refrigerant.

Pls help, 2010 odyssey ac fan not engaging, freon pressure good, compressor clutch engages blow cold air for a while buh getting warmer with time, check fuses relay ok. Test light for continuity on the fan plug shows voltage run across to the fan motor buh not spinning.

Changed the fan and realise I wasted money cos 12 v Direct from car battery spinned even the old fan. Somebody pls help

My blower wasn't also coming on removed the ground wire scraped the case bare ,reattached grd it's a ok now check the ground