So my defroster just quit blowing. It worked a week ago during a rainstorm, but stopped. I'm not sure if it is something I did under the dash while checking out the tach or putting a new seal on the gas pedal. I have a factory air 68 coupe, the controls have 4 vacuum hoses attached for the location (heat,fresh,defrost,max,off), but no matter the setting, it always blows from the heater vent below the dash.

Looked under the dash and the plenum is plastic, but there are all sorts of vacuum controls I have no idea what they do, the manual is pretty useless on this one. Any help would be appreciated.

 

Nothing, nobody out there has any ideas? Come on guys, sombody has to have done this before.

 

Here's what you need to do. Find the fuse for the blower and remove the fuse. Check each side of the fuse holder for 12 volts and one side should read 12 volts. If there is voltage there, then check the two wires at the blower for voltage (after you replace the fuse you took out). If not, you need to check continuity of the two wires that feed the blower cause there is a break in the line. If there is voltage at the blower, then you're blower is history.

 

Yeah, just check the voltage at the positive wire that goes to the blower at the firewall with the engine running and the heater on. If voltage there, and the ground is good and still no blower motor, then a toasted blower motor. No voltage there, then check the fuse as Slick suggested.

 

From this I was assuming that your blower motor is still working, but you just can't control where the heater box directs airflow. If the heater box is anything like it is on my 72, then there are a number of bellcranks operated by cables in order to either a) allow air to flow from the heater box into the car itself or b) direct air up to the windshield rather than the passenger compartment. I'm not positive but I think for the vac-operated units the vac diaphragms still end up moving a section of cable in order to open / close heater box vents. You could check whether the cable(s) may have broken / slipped off the appropriate bellcrank(s). Better, crawl under the dash and have someone operate the heater controls with the car's engine running, and see if the vacuum units are doing what they are supposed to do (you need the engine running in order to have vacuum source for the vac diaphragms). Also, over time these vents can get stuck pretty bad. The heater controls on my 72 work but not as smoothly as I would like.

If the motor itself is no longer working, then in addition to the other checks mentioned earlier, a simple thing to look at is the electrical connector on the heater box. I somewhat munged this connector when I took the dash and heater box out to clean up the firewall... and several times now I have just nudged this connector and knocked it loose:



[IMG]local://upfiles/47054/5213DAF1339440AFA4B969FF9C5491D5.jpg[/IMG]

 

Sorry I was not clear enough. The blower motor works fine, I cannot control where the air goes. No matter which selection the heater always blows. Apparently factory A/C cars have a different setup than normal. My other 68 uses cables to open and close heater/defroster. This one uses vaccum. There are at least 4 of these little bellshaped devices that have bladders in them attached to the crank in each of the areas (fresh, heat, a/c, defrost). Suddenly none of these works.

The manual is fairly useless, I am currently testing vaccum, but there are so many hoses it is hard to spot a problem. I'll take a pic and see if that helps.

T

 

Do each of the settings have a different vacuum pod, or are they all run off one? If they all suddenly quit working, I would think that only one pod is used to run all of the settings, therefore the one pod has gone south. Just pure speculation and brainstorming on my part.

 

The hard part is diagnosing where the problem is. The only thing that blows is the heater. If I manually active each of the dampers, they work. For now I have to go get a vaccum tester and try and figure out where/if the leak is. This is truly a dumb design by Ford, the cable method is much more reliable. Arrrrrggggh!!!