First and easiest:

The screws that hold the defroster flaps vibrate loose, and the flap assembly falls down inside the dash casing about an inch. That way, even when they are getting vacuum and closing, the airflow is not restricted by the demister flapsto the screen. This decreases air flow to the center and end facia outlets.

You could well be correct that this is a vacuum fault. The vacuum solenoid for the demister flaps in on the LH side (if memory serves), there are two solenoidson each side and the one you are looking for will have a green vacuum pipe (defrost).

If your demister flaps are properly mounted in the dash, apply vacuum to the green pipe and they will close (normal state unless defrost is selected). If not, that is a dash-out job to access for repair or replacement.

If they work, test the vac. solenoid with the green pipe for proper operation. These fail commonly, and are sold new for outrageous money and only in pairs. I know a guy who can help you further, private message me if you need more assistance.

Any significant loss of vacuum to the system (failed center facia vacuum dashpot, vacuum check valve corroded by battery acid, etc.) will cause the defroster flaps to stay open all the time. Good hunting.

Andrew Bernstein

 

My bet is the center flap vacuum pod.

 

Reviving an old post here as I seem to have the same issue on my 1992 XJ6. I get air coming out the foot well and defrost vents all the time. In my case however, changing the setting to full defrost puts all the air to the defrost and it is strong air. When I put it to normal setting for the fascia vents, I get a low level of air coming from the defrost and foot well. I am thinking the vacuum is good or it wouldnt change the way it does when I put it to defrost. I am hoping it is just the screws being loose like you mentioned but dont know where to check for this. Can you point me in the right direction? Thanks in advance!

 

Hi etaent,

In my experience, it is not that the screws holding the defrost vent flaps work loose, it's that the plastic dowels or "pins" on the ends of the flaps nearest the center vent break off due to fatigue and the spring tension of the actuator solenoids. There are various hack repairs that have been satisfactory for some members. I removed the dash on my '93 and repaired the flaps by drilling through the broken pins and resecuring them to the flaps with small stainless steel screws and plastic glue. This also gave me the opportunity to do several other jobs, like cleaning all the deteriorated foam weatherstripping out of the space between the heater core and evaporator and elsewhere, to thoroughly clean the evaporator drains, to test all the blend flap actuators, to replace the tweeters in the dash, etc. It's actually not as difficult as you might think to remove the dash, but if you really don't want to do that, search for some of the hacks like pulling the defrost flaps out through the center vent.

Cheers,

Don

 

Thank you for the advice Don! You always come thru with a wealth of helpful information! I am going to remove the grill first and see what I see. Hopefully it isnt something too involved and I can avoid having to take down the dash. I will report back what I find.

On another note, do you know how to change the title on posts to say "RESOLVED"? I have a few that were resolved but dont remember how to update the titles, lol!

 

I think the editing function times out, so by the time most topics are resolved, the original poster can no longer edit the thread. If you will send me threads that are resolved via private message, I'll mark them RESOLVED for you.

Cheers,

Don

 

I think someone did a thread on a 94 where the defrost panels had broken and fallen into the flaps. JBWeld was/ is a godsend there.