99 expo air direction problem from def,to the floor to the panel

[expo dude]

i recently have had the heat or cool zone selector stay on the defrost mode will not change zones to the floor panel etc. could anyone please help me. when turned to ac mode it still works and kicks on the ac but the zone stays at the windshield will not go to floor or anywhere else except stays at the windshield in ac mode or heat mode all windshield

 

[bedrck46]

which model expy do you have
eatc or manual controls

 

[expo dude]

i want to believe its the manual vacuum system mine had the knobs for the controls and vacuum lines behind the selector knob control

 

[JUST4FUN]

look around the battery area for vacuum leaks sometimes the acid from the battery melts the lines

 

[expo dude]

thanks for the info ill look at that

 

[expo dude]

the vacuum lines going into the firewall all appear to be in good shape all the way to the engine and any connecting lines in the same path

 

[expo dude]

just took the control area apart dont seem to have any vacuum suction at the black hose also no suction at the connector drivers side floor where the connector is to the cluster assembly at the black connection of the vac assembly hose connection is there further checks or possible areas of a break or loss of vacuum pressure.

 

[expo dude]

p.s. it worked through the winter months and the year before this is a recent issue i have had

 

[stamp11127]

To quote Sherlock Holmes 'There is nothing like first-hand evidence.'

Apparently the black line isn't as good as you thought Watson....

It is either disconnected or broken between the engine and the control valve.

 

[expo dude]

where abouts is the control valve on this truck for the system sorry i am new to the hvac system trying to learn as much as i can

 

[expo dude]

so very tight space where that line comes into the truck but i happened to find the vacuum line that went through the dash and all is connected i am unsure at this point it just all of a sudden wend down and stopped working correctly

 

[expo dude]

i was able to track the line through the dash witch was not easy at all and all seems to be connected i dont know if there is a crack in the line or not due to not wanting at this time to take the dash out ughh

 

[stamp11127]

Check for vacuum at the source then work towards the controls. At some point you won't have any.

 

[JUST4FUN]

Did you find the vaccum reservoir round ball under the battery? run the truck then shut it off then listen by the battery for a hiss

 

[expo dude]

i found the vacuum reservoir ran the truck didnt hear a hiss near the battery

 

[expo dude]

but i do know its hooked up i followed them lines as well maybe it has a leak?

 

[stamp11127]

Just because it is hooked up at the engine doesn't mean you have vacuum at the port. Pull the line off and check for vacuum while running. If you have it there then check at the reservoir.