Auto Air Conditioning & Heater Repair: 1996 silverado air conditioning, electronic leak detector, rubber tube

Question
my truck keeps losing freon I checked it for leaks and cannot find the problem.I did notice something drip from under the dash it looked like a brownesh fluid with no smell.Any suggestions.Thanks.

Answer
What did you check it for leaks WITH ?.

The most logical place for a leak is at the evaporator.  Locate the condensation drain rubber tube that sticks out oof the firewall into the engine compartment and points towards the ground and using an electronic leak detector see if your leak is there.