azwidemind Report post Posted February 8, 2012 2006 Mandalay on Freightliner chassis - vacuum pump that controls heater and air controls keeps running. Serviceman tells me it has a bad vacuum port, not a pump, but a port. Can't seem to find one. No one, even Thor, seems to know what I'm talking about. Anybody out there ever heard of lone of these things? Where can I find them? Share this post Link to post Share on other sites
wolfe10 Report post Posted February 8, 2012 Azwidemind, Welcome to the FMCA Forum. The vacuum pump "powers" the vacuum motors that tell the air in your dash HVAC system where to come out, recirculate/not recirculate, etc. And if one of the vacuum motors OR a vacuum line to one has a leak, then, yes, your pump could run all the time. No big thing to trace. Access the back of the HVAC panel. Pull the vacuum line from the pump and block it off. Turn on the ignition. Pump should run and pull a vacuum, then shut off. If not, the problem is in the pump or the line from pump to HAVC controls. In some older installations, there is a remote vacuum switch that turns the pump on/off that also needs to be checked. If it holds a vacuum, reattach the vacuum line and listen for a vacuum leak at the HVAC control. If none start checking each vacuum motor/line to them for a leak. I would ask your coach maker for the name of the company that provides your HVAC controls. Many have on-line diagrams and troubleshooting help. Brett Share this post Link to post Share on other sites
