A/C
Thread Starter
|
New User
Joined: Jan 2007
Posts: 12
Likes: 0
From: Moore OK
A/C
I recently got my a/c working in my 78 f-150 after overhauling the compressor. But just like before,when I am driving and accelerate,It starts blowing out of the defrost then let off it blows out of the vents. I changed all the switches under the dash but no help.
Freshman User
Joined: May 2007
Posts: 43
Likes: 0
It's because you're losing vacuum. The climate control doors run off of little vacuum actuators and the vacuum is sourced from the engine. Under hard acceleration, there is little to no vacuum in the intake manifold and the control door actuators will move back to their default positions.
You can change this by ading a vacuum canister in line with the vacuum line that runs from the engine to the climate controls. I would also install a one way check valve on the engine side of that canister so that the vacuum in the canister isn't lost under hard acceleration.
You can change this by ading a vacuum canister in line with the vacuum line that runs from the engine to the climate controls. I would also install a one way check valve on the engine side of that canister so that the vacuum in the canister isn't lost under hard acceleration.
Posting Guru
Joined: Sep 2003
Posts: 2,313
Likes: 12
From: Northeast LA
IIRC your truck should have something like that already. Again IIRC on some trucks it looks like a coffee can and on some trucks (mine) it looks like a black ball that's mounted on the drivers side fender up around the ignition module area. I could be wrong on the coffee can and location but I know on mine it's a black ball on the fender.
Posting Guru
Joined: Feb 2007
Posts: 1,735
Likes: 2
From: Wingo, Ky
There should already be a container under the hood that stores vacuum. Maybe there is a hole rusted through it. I think they have a check valve to hold the vacuum, so that could be bad. You should be able to shut the vehicle off and all the controls still work until the stored vacuum is used up.
