Where is air cabin filter located on 99 isuzu rodeo?

Its usually behind the glove compartment in the blower box. you will have to pull the GB door down all the way to access it

There is only a pleated paper filter that is not replaceable. The only reason that I know it is there is because I ripped the dash out of one in the junk yard to get at the instrument panel. However, you can't order a replacement, so I think that is was meant to more or less keep large debris out of the system and not actually filter the air.

Hopw this helps ya!

There may be a filter behind the glove box, and if there is, you need to remove the whole GB and hinge to see what's behind all that. It's likely that such early model Isuzus have no replaceable filter, but if you disassemble enough of the airbox, you just might find something that you can replace with a small engine air filter, but you would need to measure the airbox filter, then search the Web for an engine filter of the same dimensions. It's possible...
Carcarekiosk.com says of the Isuzu Rodeo 98-04:
"Our research indicates that your vehicle does not have a cabin air filter (also known as a pollen or AC filter). Vehicles without cabin air filters typically have a plastic mesh that prevents leaves and other foreign objects from entering the HVAC system. This mesh is part of the vehicle and does not need to be changed."