97 Aerostar a/c problem dual air

97 Aerostar, 3.0L, dual air
front A/C works at engine low speed but not when engine is at higher speeds but starts working again when I take power away. A/C clutch?

also the rear A/C has stopped working but I can hear the fan and no air is coming out. need to know if someone had similar problems and what fix was done.

Thanks

maybe it's a relay on the fan, woke up this am and it just popped into my mind will check it out.