heater controls,air from defrost only?

[99SD]

my slector for the vents wont work. where should i start looking

 

[JLDickmon]

black vacuum line that comes in the right side of the cab under the air plenumn...

trace it back to the POV solenoid under the hood and the vacuum reservoir if you have to...

 

[Tail_Gunner]

my slector for the vents wont work. where should i start looking

Is all the air coming out the defroster vents?

 

[99SD]

Is all the air coming out the defroster vents?

yes all the air is coming out the deforst vents. it doesnt matter what setting you have the vents on it alway comes out the defrost

 

[Tail_Gunner]

yes all the air is coming out the deforst vents. it doesnt matter what setting you have the vents on it alway comes out the defrost

OK, then you have a vacume problem most likely. The condition you describe is a "default" condition. Ford figures having defrosters is more imortant than heat or vents.

On the passenger side under the hood, you'll find the electric vacume pump. I'm guessing it is running continuously due to a leak some where. (If it ain't, start looking for fuses) 1st I'd remove the vacume hose from it and put a finger over the port to see if it builds vacume and shuts off. If it don't, then the pump is bad. If it does shutoff, then just start chasing the routing of the vacume hoses and look for loose hoses or holes.

The most typical area is with the vacume hoses that go to the solenoid for the automatic front locking hubs and then continue down to the hubs themselves. I'd try removing the vacume hose that goes to the solenoid and plugging the port at the vacume cannister source. That automatic hub system is a "Class A" P.O.S. and almost always cause problems sooner or later. By isolating the entire system, I'd say you stand a better than 50% chance of finding your problem.

 

[99SD]

thanks for the info. i will try to trouble shoot the problem

 

[99SD]

OK, then you have a vacume problem most likely. The condition you describe is a "default" condition. Ford figures having defrosters is more imortant than heat or vents.

On the passenger side under the hood, you'll find the electric vacume pump. I'm guessing it is running continuously due to a leak some where. (If it ain't, start looking for fuses) 1st I'd remove the vacume hose from it and put a finger over the port to see if it builds vacume and shuts off. If it don't, then the pump is bad. If it does shutoff, then just start chasing the routing of the vacume hoses and look for loose hoses or holes.

The most typical area is with the vacume hoses that go to the solenoid for the automatic front locking hubs and then continue down to the hubs themselves. I'd try removing the vacume hose that goes to the solenoid and plugging the port at the vacume cannister source. That automatic hub system is a "Class A" P.O.S. and almost always cause problems sooner or later. By isolating the entire system, I'd say you stand a better than 50% chance of finding your problem.

ok when i take the line off the pump it will shut off and then surge. does that mean the pump is bad???
i did a vacuum test on the hubs and they held pressure for 30 mins

 

[99SD]

any body have any ideas

 

[CHPMustang]

On my 99 F-550 the vacuum hose popped off the solenoid doo hickie behind the glovebox that is attached to the AC blend door unit. At the time the 99 was totally new to me and had to take the truck into the dealer where the tech found it very quickly.

 

[bushpilot]

sounds like youve done a good job of isolating the problem...
you know now its NOT the hubs...id chase all the vac. lines
into the cab and make sure none of those is leaking or disconnected.