Vent thru Defrost Only

[Gloffer]

A coupla weeks ago my ventilation started blowing through the defroster vents only. It doesn't matter whether it's heat or AC, vent or auto, everything comes through the defroster vents under the windshield. Sometimes when it's transitioning thru heat to cold it will momentarily blast through the dash vents, but it shifts back to the defroster vents quickly.

It's putting out hot or cold air depending on the need, meaning that the AC and heater are working fine, but it's only out through the defroster vents. I ran the HVAC self check and it indicated normal function. Is there some vacuum hose or other gizmo that I can check to get this working before I take her into the local shop?

Thanks,

 

[sdpatt]

The defroster damper actuator is not closing the damper. It may not be getting a vacuum supply either from the ECC head unit or the engine. The other possibilies are that the damper linkage has come loose (behind the glove box toward the driver side and forward to the firewall), the diaphragm has failed in the actuator or the ECC has failed. You can run the climate control diagnostic test from SHOtimes to determine if there is a detectable error.

 

[projectSHO89]

Scott mentioned the vacuum supply...

There is a vacuum line that is routed through the firewall through the same hole as the heater core hoses. Locate this hose and verify that it has not come loose. Since it sounds like something is trying to move the panels, there is evidently *some* vacuum the unit.

For safety reasons, airflow is directed to the defrost vents whenever the system fails. This is normal.

If you determine that it is the vacuum actuator, good luck. It is really buried in there and will likely require that the dash be pulled back.

You can do some testing of the actuators with a vacuum pump via the opening in the dash. You have to remove either the ETAC or the heater control panel to reach the vacuum line connection.

Steve

 

[Gloffer]

I ran the diagnostic and it came up clear. Must be a vacuum or mechanical problem. I was afraid of that, and the repair doesn't sound like any fun. Are there any detailed instructions on the site for removing the EATC/heater control panel, and if the worse comes to worse the dash? Might be a good time to replace those burned out dash lights too.

<small>[ January 07, 2003, 05:33 PM: Message edited by: Gloffer ]</small>

 

[Gloffer]

I've evaluated this a little further and here's some updated info that may aid in diagnosis. (I'm really trying to avoid removing the dash, unless it's absolutely necessary.)
As far as I can tell, at the firewall there are 3 holes for the heater hoses/vacuum line. One for the heater hose in, one for the heater hose out, and one for the the very thin plastic vacuum line located right between the two heater hose holes.

This vacuum line is fed from a TEE that is mounted to the firewall, I couldn't quite see where the other two ends of the TEE are routed to, but I assume one is the vacuum supply and the other goes off to some other vacuum operated accessory.

I noticed that the ventilation will shift from the defroster vents to the dash vents under high engine vacuum conditions, like lifing off the gas when coming to a stop, and sometimes when just sitting at idle.

Would this indicate a vacuum leak that I could fix under the hood or under the dash without removing it? Or does it mean the actuator diaphram is weak/leaking and needs a high vacuum to operate?

Thanks for any advice you provide.

 

[Bob S.]

Sounds like a vacum leak. A small one doesn't affect the engine too much as the computer will compensate. Follow all the vacum lines from the manifold and make sure none are cracked or disconnected. There are a couple of one way valves in the system, if hooked in backwards they will block the vacum from reaching the actuators.

Not sure where the vacum resevoir is located, but on other fwd gen1 Taurus's and the Continental it is located in the passenger side front wheel well. The vacum line to it runs along the fiewall and disappears into the back of the strut tower. On my wife's continental the factory never connected it.

Bob

At Ford quality is Job !, too bad they only hire for jobs 2 thru 99.