Corroded relay.Cant find replacement.GQ

My air con was running OK, but on a recent trip it suddenly stopped putting out cold air. Everything else on the truck works as if it were new ( heater, fan,power windows etc), so I thought I would have a look around.In the "relay bay" next to the battery I found a metal 4 pin relay flapping about. It was in the corner and sitting in an inch of sand, red dirt and water and has probably been there for 5 years and has rusted diagonally and corroded away, taking all part numbers with it except the 12V 20A label. All the fuses in teh drivers kick panel are intact.I have removed the relay but cant get a replacement. All the other relays in the relay bay are coloured and plastic, so I think this one must be a replacement by a previous owner ( and the wiring around the engine bay would indicate they loved to wire stuff up!).
I have looked in the manual but it does not tell me which pins do what. Can I short out the pins to test the air con running. Presumably I will have to cut the plug off and wire up a different relay.
Any help or guidance would be welcomed as the wife doesn't believe thta winding the windoews down is the same as working air-con.

Can you see any numbers near the pins of the relay? such as 85, 86, 30 and 87?

Is it a Bosch relay?

Nothing apart from part of a logo ( circular) on one side. I will take a couple of photos tomorrow and upload them.

Does it look like the Hella logo?

Some photos might help.

Are you sure this relay is for the A/C? have you followed the wiring? does it go to the A/C compressor or condenser fan?

Is it a genuine A/C system?

Your A/C system might be out of gas.

Here are some photos of the relay. You can see the corrosion.
Can I short 2 pins together on the loom to see if the air con is working? If , so , which ones.
As I mentioned, I'm not even sure what the relay is for , I just found it connceted and laying in the tray. I drive to work at Carole Park ( about 45km each way ) each day and have no problems with the car electrics since I removed the relay , so it must be an accessory I'm not using . The spotlights & 2nd UHF have been removed by a previous owner and they left the switches etc in, so it could be that.
Does anyone have a photo of the air con relay and nits mounting point , as it may not be related to that fault at all. My car is the Ford Maverick, so not sure if that makes a difference.

This should be enough info to get you sorted
http://www.autoshop101.com/forms/hweb2.pdf

If you can remove the metal part of the housing you will see a set of contacts, similar to points but not as rigid.

You should be able to see which two pins connect to these contacts. These will connect to pin 87 and 30 of your aftermarket replacement relay.

These two wires are also the wires you can temporary join together to see if your A/C will work.

The other two will connect to the coil part of the relay, these will connect to 85 and 86 of your new relay.

Hope that helps.

Cheers Rodney