That's something you will have to look up Vehicle specific, displacement specific, and application Specific....
Not all "Ford" relays are the same..they vary from application to application..
Most automotive relays range from 30 amp on up to heavy current handling relays..in increments of 10 amps..If you had to guestimate..go with a 40..unlike fuses, too big is better..
The other way to tell, is pull the relay, look on the bottom or side of the relay for a data plate that looks like this:
- Coil: 12 VDC
- Coil Draw: 1 amp.
- Contact rating: 250 VAC/DC (Arc over or weld point)
- Contact Current Max: 30 amp. (melt down point)
Or it may have one of hose Day~um cryptic Ford numbers like : CAE~0006724~8946234~268947`30
, That you need an Enigma Machine , Code breakers at Heathrow, and the French underground sending coded messages to "Kinch" at stalag 13 , to relay to Hogan to Decipher
...to cross it over to an item we humans can deal with..