Vacuum issue

[nylyon]

So the past couple of weeks I have had an interment issue where the heat would only come from defrost. Since I do not have automatic hubs (replaced with Warn) I began to troubleshoot. I think that I found the problem right away but want to validate. From the Vacuum pump the line goes to a connector attached to another box. There are 2 lines from this box one goes to the cab, the other to a relay then to where I suspect would be the front hubs.

Anyway, I disconnect the vacuum connector from this box and I have vacuum from the port. If I "jump" between the two ports, I get vacuum throughout the system (heater works properly). So my question is: Is this box a vacuum amplifier or something? Also I suspect that it is bad, does anyone know the part number for this thing?

Thanks.

[nylyon]

I borrowed this from another site / user so credit for this picture goes to partsguyed.com on Ford-Trucks.com.



Part number 9E453 is what I am talking about. It's a vacuum reservoir. I only see the vacuum connection on the top. Does anyone know if there are additional connections and / or what the full part number would be for a 2003? When I "bypass" this part all is well, so I am thinking this is the culprit, but before I go buy the part I like to be sure of the part number. Thanks.