To all that replied on this so far - the OP mentioned that his car has the I/C isolation mod and the fluid lever is set to "off". I don't have the isolation mod, so I don't know how it operates, but could it be a simple turn of the lever? I find it odd that the previous owner modded all that stuff and didn't change out the I/C pump? I guess even an updated pump could go bad, but I would try the cheap fix before throwing parts at it.

Just my dos centavos