How to fix vent from turning to defrost?

Asked by Jul 09, 2016 at 09:26 PM about the 2003 Ford F-150 Lariat Crew Cab 4WD SB

Question type: Maintenance & Repair

Dash vent works when at idle or real low speed, accelerate and it goes to
defrost.  If the panel floor button is pushed, then vent works and floor portal
freezes your foot. How can you determine if it's the vacuum lines or the dash
box controller?

1 Answer

68,615

This is going to be a vacuum problem. Intake manifold vacuum is strongest at idle and decreases as you accelerate. There's supposed to be a check valve and possibly a vacuum reserve tank in the system to combat mode fluctuations. The check valve is usually in the vacuum line that runs from the engine, through the firewall, and to the climate control panel on the dash. It will look like a little plastic disk. If you have a vacuum reserve tank (some systems do and others don't) it'll most likely be in the engine compartment and look like a plastic ball or box with 2 vacuum lines connected to it. It may even look like a coffee can with 2 vacuum lines connected to it. HTH. -Jim

Your Answer

Add photo

Related Questions

Search Ford F-150 Questions

Ford F-150 Experts

#1 OJ
OJ
Reputation 8,490
#2 dandyoun
dandyoun
Reputation 4,420
#3 tennisshoes
tennisshoes
Reputation 2,950
View All

Related Models For Sale

Used Chevrolet Silverado 1500
1,950 Great Deals out of 183,196 listings starting at $1,495
Used GMC Sierra 1500
774 Great Deals out of 68,743 listings starting at $1,800
Used Dodge Ram 1500
419 Great Deals out of 10,970 listings starting at $1,000
Used Ford F-250 Super Duty
334 Great Deals out of 44,556 listings starting at $1,450
Used Toyota Tundra
449 Great Deals out of 34,804 listings starting at $2,500
Used Toyota Tacoma
553 Great Deals out of 43,264 listings starting at $1,995
Used Ford Mustang
696 Great Deals out of 44,783 listings starting at $1,500
Used Nissan Titan
174 Great Deals out of 19,030 listings starting at $3,995
Used Chevrolet Colorado
247 Great Deals out of 27,664 listings starting at $1,000
Used Chevrolet Tahoe
582 Great Deals out of 33,058 listings starting at $1,500
Used Ford Explorer
912 Great Deals out of 64,625 listings starting at $799
Used Ford Ranger
174 Great Deals out of 5,598 listings starting at $900
Used Ford F-350 Super Duty
384 Great Deals out of 24,304 listings starting at $2,588

Used Cars For Sale

2018 Ford F-150 For Sale
862 listings starting at $29,070
2017 Ford F-150 For Sale
65 Great Deals out of 124,330 listings starting at $18,199
2016 Ford F-150 For Sale
120 Great Deals out of 9,501 listings starting at $14,950
2015 Ford F-150 For Sale
214 Great Deals out of 8,901 listings starting at $15,990
2014 Ford F-150 For Sale
349 Great Deals out of 12,529 listings starting at $9,900

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.