Help with 1990 Ford F-150 vacuum issues

[montesa]

My 90 ford vents only blow from the floor. The system runs on vacuum and two actuators.

I replaced and checked all the lines I can get to. There is no vacuum at the actuator under the hood near the blower motor and no vacuum at the actuator in the cab near the passengers feet. I can’t feel it at least.

Are any of you guys familiar with this system? I’m assuming the issue is related to the switch in the dash and how it directs vacuum to the actuators.

 

[Okie4570]

My dad had the same truck and after he passed away I brought it home and drove it for a few years. The last year I had it I went the the same thing, attempting to find all the leaks and took it to a guy and he couldn't make it work right either. Hard acceleration and it switched from the dash vents to the defrost vents.

 

[montesa]

My dad had the same truck and after he passed away I brought it home and drove it for a few years. The last year I had it I went the the same thing, attempting to find all the leaks and took it to a guy and he couldn't make it work right either. Hard acceleration and it switched from the dash vents to the defrost vents.

Well, maybe I’ll need to become the expert on that then. I brought it to one mechanic that said it would be no problem and he knew less than I do about. Got another in harrah that I’m going to take it to. If he can’t figure it out I’ll take the dash apart and figure it out. Might be easier to run cables to the flaps. It’s a lot of hassling with vacuum hoses to open and close a couple of flaps. Also, I think the vent selector also switches the power the blower motor based on vacuum so there’s an additional complication. Would rather the blower motor ran when the switch was on no matter what.

 

[Snattlerake]

Drawn out but he shows both lines to replace because he broke both.

 

[montesa]

Snattlerrake, yes those lines are replaced and solid. No leaks there. First thing I looked at and one of the first videos I watched. Thank you for looking it up and posting it though. Appreciate it.

 

[tyromeo55]

It’s step is to Pull the selector panel and see if you have vacuum there

 

[NightShade]

Check the coffee can under the hood. Yep, coffee can. It's pained black, you can't miss it. It's the "vacuum reservoir" they develop holes over time in the bottom. You won't see them and will probably miss it.

Also if it's running rough just plug the main vacuum line and see if it runs better with it plugged, the idle should drop down a bit as well.

And remember there is a vacuum line that runs all the way to the fuel tank it's probably plastic with a rubber hose near the end.

 

[montesa]

Check the coffee can under the hood. Yep, coffee can. It's pained black, you can't miss it. It's the "vacuum reservoir" they develop holes over time in the bottom. You won't see them and will probably miss it.

Also if it's running rough just plug the main vacuum line and see if it runs better with it plugged, the idle should drop down a bit as well.

And remember there is a vacuum line that runs all the way to the fuel tank it's probably plastic with a rubber hose near the end.

I sealed the coffee can with epoxy last week. It developed a crack at the part a can opener would cut. Truck runs perfectly. Starts quickly and idles spot on. Low but smooth. I also replaced the vacuum line from the manifold to the charcoal canister. I believe that’s what you’re talking about. The line from the tank to the canister is steel up until the last portion and it looks perfect. I think the problem is in the dash and related to the switch.

 

[montesa]

It’s step is to Pull the selector panel and see if you have vacuum there

I think this is correct. I started to but there were cables attached that I wasn’t sure how to disconnect so I let it be for now just to not make a new problem.

 

[SdoubleA]

The dash selector switch is probably the culprit.