AC problem

[Van I.]

My AC was converted to the new type 2 years ago by ford and it worked just fine. Now I have a problem. When I turn on the AC, rpms drop from approximately 750 to around 500 and the truck seems like it is going to die.
Battery was replaced about a year ago and alternator was upgraded to 130 amp at the beginning of this year. Belt was changed when I changed the alternator.
Any ideas on what may be causing the rpms to drop when the system cycles on and off? Summer is on its way, and here in Hawaii we are in the high 80's already so I need my AC.

Thanks for any help in advance,
Van

 

[NOTAJP]

The rpms should drop slightly with the load of the compressor, however, the engine should compensate for the extra load. Check your clutch to see if it's turning properly. Check all your fuses and electrical connections. That should give you a start.

 

[Robert]

Also don't forget about your idle air control valve (IAC). It is the device that actually controls your idle and adjusts your idle when a load is placed on it (such as from the A/C). When it is starting to fail, it won't be able to control your idle like it should.

 

[Van I.]

Thanks for the replies. I'll check on your suggestions.

Van