Broken vacuum line next to yellow line for heater door

200,000 MILES • 3.0L • V6 • FWD • AUTOMATIC
Avatar
USAF_SES
  • MEMBER
  • 1 POST
I had a garage do some engine work in the summer and have not needed to use the heater until now. Switching from defrost to any other setting besides OFF makes no difference.. The door position does not change. During a visual inspection, I noticed the yellow vacuum line (very tiny plastic line) was intact but there apparently used to be a black line next to it (under the hood near the passenger side upper firewall). I cannot find where that line comes from.... and I am assuming it is part of the problem. Where does it go? I looked all over the firewall but don't see the other end of it hanging anywhere. And could it be the problem? I am an engineer, not a car expert..... please let me know because otherwise it is going to be a cold winter. I cannot afford an expensive repair, which is why I still have a 14 year old car that needs to last until the Spring.
Dec 27, 2014 at 4:03 AM
Avatar
CARADIODOC
  • ✓Experienced Mechanic
  • 34,398 POSTS
There's a vacuum hose routing diagram under the hood that will show that hose. Ford typically used a black can about the size of a large tomato juice can mounted on an inner fender for a vacuum storage tank. A vacuum hose goes from that can to a plastic tree on the firewall, and another hose goes through the firewall to the heater control switch.

Most systems are spring-loaded to go to defrost mode as a safety measure when there's a problem with the vacuum source. Your feet might freeze but your windshield will be clear.
Dec 27, 2014 at 8:01 AM
Add a reply
Join 2CarPros for free, one of the most advanced car repair communities on the internet. From first-time drivers to seasoned mechanics, everyone is welcome to reply, share details, and get better answers. You can add a temporary image or video first; uploads are limited to 20 MB.

Frequently Asked Problems for This Vehicle