Odd issue: When turning on blower fan, flaps close?

This is kidna crazy and Im unsure on where to start. When I turn on my heat to the defroster/windshield setting and the blower is over setting 1 ( 2-4 is no good ) the force of the fan blows the defroster flaps closed. Then it stops blowing out of the windshield vents.

Does anyone know where to start to troubleshoot this? I dont know what controls what to hold that flap to divert the air to the defroster/windshield.

Note from DJ
Let’s play a game.
From http://www.naxja.org/forum/showthread.php?t=1025356
Post #2 by joe_peters
“Let’s play a game.

You pretend that you are the only one that knows what year/engine, etc., that you are asking about.

We will all pretend you never asked a question until you provide at least the bare minimum of information about your vehicle”.

Ironically, djgrayxj provided less useful info than the OP did.

It sounds like you have 2 different problems going on. The flaps closing could be a blend door issue. Usually when the resistor for the heater selector goes out it only works on full blast (zero resistance). More info about your Jeep will be very helpful.

Note from DJ
My post was a “QUOTE”; by joe_peters that I had saved because I thought it was a very funny statement to a previous poster.

I copied and pasted Joe’s statement as a hint to OP NattyBoh that we needed more information about the XJ [I think it’s an XJ]? With the problem.

I cant believe that I missed that.. Its for a 1997 xj sport. Its a 4 door with the I-6 engine. Anything else? It has AC too.

It blows heat no matter what. the issue is, if I go over the 1st fan speed ( the slowest ) on the defrost/window setting the air overcomes the flap that sends it to the windshield. If it is on any other vent/setting all is well. Im just having an issue with the defrost setting.

bump

Have you made sure that the vacuum line is connected to the ball canister under the bumper on the passenger side and there's no cracks in the lines running down near the battery? My 97 was doing the same thing. I found cracks in the vacuum lines near the battery and the line had disconnected from the ball.

lol i dont think i even have that. i have a JCR bumper on there.

I have the same issue with my '98 XJ 4.0 auto. Been like that for a number of years.

The heater and AC temperature work fine, so I think the blend door is OK.

The knob that controls where the air flows works OK (vents, defroster, etc.) - that is
until you increase the fan speed to #3 or above. At #3 or above, a flap can be heard
to "clunk", and the air flow is cut off and the fan cavitates and spins faster. Shutting
everything off resets the flap open and so I'm limited to using the fan at the #1 or #2
setting.

I've checked the vacuum bottle under the bumper. When disconnecting the hose at the
bottle you can hear a "hiss" (= loss of vacuum) so I think that there is no leak in the
hoses. I checked the vacuum hose that runs under the battery. No cracks or anything
unusual there, either.

When the AC is on, I can hear a whistle under the hood - just like a vacuum leak would
do, but it goes away whenever I stop and open the hood for a look-see, and so I've never
been able to put my finger on where the whistle is coming from.

I'd just about given up but this thread has renewed my interest for a resolution.

Sorry, I have no solution to offer.

haha yeah man exact issue. There has to be way more people with it too and thus have a remedy...

free bump. had this happen with my TJ and my XJ. I can't be of help cause Im just gonna do a AC and Heater delete. unless you get a good answer.

bump

Hmm, I have same issue...anyone?

djgrayxj said:

Note from DJ
Let’s play a game.
From http://www.naxja.org/forum/showthread.php?t=1025356
Post #2 by joe_peters
“Let’s play a game.

You pretend that you are the only one that knows what year/engine, etc., that you are asking about.

We will all pretend you never asked a question until you provide at least the bare minimum of information about your vehicle”.

Click to expand...

I like that quote DJ, and will be using it in the future. I miss Joe.

cruiser54 said:

I like that quote DJ, and will be using it in the future. I miss Joe.

Click to expand...

ditto on both points^^

check under the dash-- there's a vacuum diaphragm that actually moves and holds the air director door in place. I would make sure the diaphragm is solidly attached to the door and that it will hold vacuum in the "defrost" position.

I've never had to check one in a specific position, but I would think that if you move the door to defrost and hold your finger over the vacuum port, it should hold the door firmly in place. A free swinging door should indicate a bad diaphragm.

Bad vacuum valve actuator attached to the damper door, or a vacuum leak in the vacuum lines under the dash or the hood (those are so fun to chase down, as they are everywhere, LOL), that becomes critical durring acceleration has been the common cause.

The last time this happened to me it was defective brand new vacuum hose that was not smooth and round on the inside of the hose that I used for repairs near the AC expansion valve. That was a fun one to find, so just because the part is new, does not mean it is not a POS!!! LOL