There was an aftermarket device that turned off the ac compressor when one accelerated... it worked off vacuum... and it was one of the few gizmos which the independant testing agencies said actually worked to save gasoline.. I do not know if the unit could be made to work with diesels... but the company that made it might know...this device is at least 20 years old....I am sure I saw it and other items which claimed to save gas in something like Popular Mechanics magizine, etc... Greg

Ok,, try this site...

http://www.ftc.gov/bcp/conline/pubs/autos/gasave.htm#**

it is in the category of "accessory modifiers" ...they are evaluating it just in terms of saving fuel without increasing emmissions... but the point is there may be some devices which will automatically cut out the ac compressor depending on how hard you put the accelerator down...