01 diesel. blower only flows air thru defrost vents. can manually stroke valve to flow air to feet.air pump under hood runs until i unplug line and cap is there a fuse which activates a relay that iam missing

 

You have a vac leak. Chances are it is in the lines that are going to the ESOF. With a vac leak the heat automatically defaults to defrost.

 

That air pump is actually a vacuum pump and if it's runs all the time, then Jim's right and you have a leak. The ESOF should only leak when you try to use 4x4. If it leaks all the time, then you may have a bad pump, or the line going to the HVAC contols may be leaking.

 

The vac system has two subsystems it supports, the ESOF (4x4) and vent systems. You need to isolate which part of the system has the leak. First thing to do is pull the line off the vac pump and cover it with your finger to make sure the vac pump pulls a vac and turns itself off. Reconnect if working.

Next - Isolate the ESOF system. I have personally experienced a failed ESOF ctrl solenoid that resulted in the exact symptoms you are discribing. The solenoid is located just above the fender well. Follow the lines off the vac canister to it. Disconnect and plug the vac line going to the solenoid. This will effectively remove the ESOF system from consideration. If the pump turns off you've identified the offending subsystem.

If the problem persists you need to start following lines back into the vent ctrl system..never been into that stuff before...

 

See this post from 05-01. CLICK HERE