Dan - You don't state the year car that you have, but the LH series has a pressure switch on the AC Compressor discharge line that starts the two fans running on high speed when the pressure gets to a pre-set level. Maybe this will help. This switch can be replaced easily - it screws out of the fitting, after disconnecting electrical lead. ......Bob Harris Subject: RE: IML: AC question > If the electric cooling fan does not come on the high side pressures > will go through the roof very quickly and the a/c won't cool worth a > damn. Fix the fan first.