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I have a 89 F-150 with the 302. The selector between vent and defrost for the heater hasn't worked on my truck since I bought it (stuck on defrost). Looking at it, none of the vacuum lines for the blend doors seem connected to any sort of vacuum source!
From the shop manual I found this vacuum diagram, indicating that a black vacuum line is supposed to go to the source:
Where is this source vacuum line supposed to be located physically in the truck?
I have a couple capped ends at the vacuum tree on the intake plenum where I could add a new vacuum line ... but I don't know where/how I would link them to the heater box... I wonder where the ventilation system is supposed to get its vacuum from.
Can someone show me their setup by the heater box and how the vacuum lines are all supposed to be connected?
I have a 89 F-150 with the 302. The selector between vent and defrost for the heater hasn't worked on my truck since I bought it (stuck on defrost). Looking at it, none of the vacuum lines for the blend doors seem connected to any sort of vacuum source!
From the shop manual I found this vacuum diagram, indicating that a black vacuum line is supposed to go to the source:
Where is this source vacuum line supposed to be located physically in the truck?
I have a couple capped ends at the vacuum tree on the intake plenum where I could add a new vacuum line ... but I don't know where/how I would link them to the heater box... I wonder where the ventilation system is supposed to get its vacuum from.
Can someone show me their setup by the heater box and how the vacuum lines are all supposed to be connected?
Thanks in advance,
André
If its anything like the 90s, the black line comes out the firewall with the wiring by the heater core hoses. there should also be a small vacuum tank on your HVAC case in the engine bay, small little thing with a vacuum line to it. There should also be an inline check valve leading to it unless the tank has one built in. And there should be a line then leading to the intake fitting. i think
The above is absolutely right and here are the Ford pages out of a 1990 EVTM
Shows the same as above except explains further, and refers you to another page for the vacuum source
It simply comes off the vacuum tee
It is all different if it is a diesel, I will post the gasoline pages
I have a 89 F-150 with the 302. The selector between vent and defrost for the heater hasn't worked on my truck since I bought it (stuck on defrost). Looking at it, none of the vacuum lines for the blend doors seem connected to any sort of vacuum source!
From the shop manual I found this vacuum diagram, indicating that a black vacuum line is supposed to go to the source:
Can someone show me their setup by the heater box and how the vacuum lines are all supposed to be connected?
Thanks in advance,
André
I’ll go get you some pictures of mine later today actually I need to go to get some connectors to fix mines connection there,
Anonymous12, your photos were very helpful. I don't have that 3-way tee that you have in your second picture. Not having that is what confused me. With it I can see how everything should probably connect. I'll get a T-connector from AutoZone and connect the three ends: one end to the line going through the fire wall, one end to the HVAC box, closer to driver side/middle, and one to the vacuum tree on the plenum. Hopefully that will make everything work.
My4Fordtrucks, I believe I have a white vacuum line there that comes out through the fire wall and goes to the motor for one of the blend doors. I believe that is how it is supposed to be set up. However, nothing is connected to the vacuum tree on the plenum, hence none of those things get vacuum. I will try to connect it as described above and hopefully that will fix it.
I forgot to mention that vacuum line in the top photo next to the blend door comes out of that taped bundle of stuff, so somehow it runs up through the tape and back out. I never touched that line since it was in tact and I’d have to cut the tape and stuff so I just left it planning on it going bad any minute.
I'm happy to report that hooking up the black vacuum line coming out through the firewall straight to the vacuum tree on the plenum worked for me to get the vent/defrost switch to work again.
AutoZone didn't have a T-connector, so for now I have left the line by the middle of the heater box disconnected. I don't know what that one does since it seems to not affect functionality of the vent/defrost selection. I think it may be the blend door for the floor vents.
The plan is still to get a T-connector to set everything up exactly right, like in Anonymous12's second picture with the T-connector.
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