Thanks Phong. Get hold of a ford shop manual and read - good explanations on A/C.
My EL wagon had a front seal leak for a couple years - rendered it pretty ineffective in anything over mid 20's degrees.
Different story now - has been really handy in these 40 degree plus days. Obviously not 100% efficient at those temps, but when the condensor is trying to transfer heat to surrounding air of same or higher temp, you can't expect it too.
You'll find most EF/EL's haven't had the receiver/drier ever replaced for routine A/C service, probably only leaks. This will be due to having to remove the front bar for access.