How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Ron Your Own Question
Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 36077
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
Type Your Ford Question Here...
Ron is online now
A new question is answered every 9 seconds

Ford F-150: My 92 Ford F-150 only blows air out of the defrost

Customer Question

My 92 Ford F-150 only blows air out of the defrost even when others are selected. How do I troubleshoot and fix?
Submitted: 2 years ago.
Category: Ford
Expert:  Ron replied 2 years ago.
Hello and thank you for your question, My name is ***** ***** I will assist you today.
The AC system is designed to divert to defrost when the system looses vacuum so you are likely looking at a broken vacuum line someplace from the reservoir to the control panel. The supply line at the controller is the Black line so I would start at the reservoir to make sure you have vacuum into it and out to the black supply line and if that checks okay then check the same line at the controller. See the under dash vacuum line diagram in the link below. Copy and paste the link to your browser to open it.
Have a look and post back if you have more questions and or need more help.
Customer: replied 2 years ago.
Ok Ill check that, is there a real life diagram and picture of what the different components look like and how they are routed, this is the inline 6 4.9liter. Also I found all the hoses that go to the controller on the dash, I played around with the hoses turning this on and that on, I would manually pinch one hose that see if I could make rhythm and reason I somehow not sure how much managed once or twice to get air out of the vents, normal AC and Max AC , but then as soon and I turned switch back to defrost then back again to vent it stayed stuck on defrost. What's your take on that?
Expert:  Ron replied 2 years ago.
Start first with locating the under hood storage revision by following the black vacuum supply line from the firewall over to where it connects, make sure you have good vacuum to the reservoir from the hose coming off of the intake manifold and if so make sure you have good vacuum on the black hose going into the firewall, if that checks okay then check the same black hose at the rear of the control panel. There are three vacuum motors on the AC/heater plenum, make sure all three are connected . See the link below for there routing. In most cases the leak is usually under the hood.
Customer: replied 2 years ago.
I may or may not have found the problem.... The motor... Or so we call it the valve, that attaches to the blue hose it stuggles to close when I switch to vent you can see it closes about 25% of the way, it seems like there is adequate vacuum... I don't really know how much suction it should take to actuate, perhaps the valve aka motor is bad?
Expert:  Ron replied 2 years ago.
If its slow to closes then the diagram is likely leaking and that would cause it to not close. You can test it by removing it and suck on it and see if it will close or you can use a hand held vacuum pump as well. If any one of them is leaking it will effect them all.