firestorm

Here's the deal. About a month ago, the ac quit working. We charged the system because it was low, and it worked great. Last week, it quit working again. I used my black light to try and locate any leaks, but didn't find any. This morning on my way into work, I needed to use the defroster. I was unable to change the vent from the front, to the windshield/floor. I was also unable to get heat out of the vent, even though my temp gauge read 200. On my way in, with everything off, I could hear what sounded like the blend door dropping. As if it was being picked up and dropped, over and over. Could all of this be related to the vacuum pump, and where is it located?

Peterbilt

03 and 04 have a vacuum pump, but it is used for the cruise control only. The heater/defroster system uses electric motors. Try searching on your issue. Good luck. Unlike gas engines, diesel engines typically do not have vacuum.

Pete

p.s. The vacuum pump is located on the passenger side fire wall under hood.

firestorm

Thank you. I knew diesels don't use vacuum, which is why they added a pump. My background is a heavy equipment mechanic. I didn't know they used electric motors, I'll check into that. Thanks again.