For what it's worth...
On my 1992 Grand Caravan with 3.0 and factory A/C front only...
There is a 'cycling relay' that is a back box with about 5 wires coming out. This is mounted just above the black/silver manifold where your a/c hoses go through the manifold.
This one is sorta the 'brains' of things.
There are also two relays on the inside fender just above the strut tower on the passenger side of the car.
The lower relay that is closest to the front of the car is a fan relay, which then commands the relay the higher/back relay to engage the compressor. Naturally they all need to work to get a/c.
When it's acting up, give each of those a healthy 'tap' and see if it kicks on. It will take some time and repeat testing because your a/c is supposed to cycle so you might mistake a 'normal' on/off. Also, you can disconnect and clean the relay terminals for corrosion.
My issue right now is that it seems my 'cycle' relay is having issues and causing eaither really short compressor cycles or none. (until I tap it)
It has an odd 'sensor' and wires that looks like it goes into the 'low' side just before entering the manifold. I'm not sure if I can replace it without discharging the system so I'm doing some more research.
This site is also a great resource for DIY repairs on these vans..
Friday, July 24th, 2009 AT 3:41 PM