Discussion Starter · #1 ·
2002 E350 PSD. Cargo Van. Heat/AC blower has defaulted to defrost. Blower works fine but it is impossible to change the output selection. As near as I can figure from searching the internet, this is symptomatic of a vacuum leak. I have vacuum presently at the manifold on the firewall. The brakes etc. work just fine. I have vacuum at the first junction up under the dash on the rider's side of the doghouse. The black line coming through the firewall then goes out of sight and the next opportunity to visualize the vacuum system is through the access hole in the top of the dash where you can see the lines coming out of the selector switch. I have no idea where to first check for leaks or how I diagnose the problem. There are red, yellow, blue, white and black hoses coming out of the selector switch and going to various vacuum servos located under the dash, none of which currently work. i'm certainly not the first person who has gone down this road.