Odd thing happening...

[jfrabat]

Hey, guys, I got a question to see if anyone has had anything similar happen to them...

In my rig, when the engine is under load and I am accelerating (say, when on the highway and going up a bridge or something on 4th, when I give it a bit more of gas to maintain speed), you can feel a gust of air coming from the defroster vents. The air is not heated, so it does not seem to come from the engine compartment or exhaust...

This happens regardless of speed; it depends on load of the engine (the more loaded the engine is, the more air that comes out). I took out the grill on top of the engine bay (the one beneath the windshield and behind the hood), and noticed that there are to "doors" to keep the air out, one to each side. However, in my jeep only the one on the driver side is actually working with the levers controlling the heater and fan. The one on the passanger fan is always on; could this be the problem? Isn't the "door" on the passanger side supposed to shut also when I turn all the vents off? Now, even if this is the problem, I still do not see why it only happens with the engine under load, but I am pretty sure this "door" is supposed to close as well (I tried closing it with my hand, and it will close, but it is spring loaded to stay open; I still have not taken my dash apart to figure out what is disconected and not letting it close, but if anyone knows how to get to this without having to take down the dash, please let me know!).

Anyway, I would sure as heck like to hear any opinions on the cause of this, because, as trivial as it sounds, it does mess with the cooling that the AC provides, and down here in Florida, it is getting HOT!

Felipe

 

[OutOfStep]

vacuum leak would be my guess

 

[Bounty__Hunter]

It's a vacuum problem, as vacuum controls the vent doors.

 

[Sparky-Watts]

I concur about the vacuum leak. It would be more noticeable under acceleration or heavy load, because your engine in pulling a heavier vacuum at the time.

 

[jfrabat]

I'll check the vacuum lines then... If that is the problem, great! But if it is the vacuum lines, wouldn't it affect both vent doors and not only the one on the passenger side? And also, I noticed that the vent door on the driver side works with the engine off, so it seems to be cable operated (right?). In any case, I'll check all vacuum lines just to be sure.

Thanks for the feedback!

Felipe

 

[Sparky-Watts]

So, what did you find? The vent door on my YJ on the driver's side doesn't operate anymore, but I don't know why. It's always open now, and yes, I think it's cable operated, too. Never could figure it out, so I just gave up on it. I first noticed it after I had some bozo fix a wiring short under the dash, and he had disconnected all of my vacuum lines to the heat/defrost ducts. I fixed them out in the middle of Louisiana at 3am on a deserted stretch of 2-lane backroad while I was on my way down to do Katrina relief. Lemme tell ya, there's some strange soundin' critters out in those parts at night!

 

[jfrabat]

Well, I am currently in Tokyo, so I have not had a chance to fool around with the Jeep, but I do intend to give it a look after I return to Miami. I am not sure if it is cable operated or not; I will take out the grill and see if it closes with the Jeep's engine on (maybe that is why it is stpring loaded; so that it can run off the vacuum), but I still think it is cable operated, because the other vent door is cable operated. If I cannot find it, I may need to take the dash out, and that's a BIG PITA! So I will probably do the e-fan conversion before I tacke that one (since I already got all the components in the garage).

By the way, does anyone know where I could find a schematic of the operation of this vent so that I know where to look for problems?

Felipe

 

[Sparky-Watts]

Tokyo?!? :shock: What, did you take a wrong turn on the way to the mall?

:lol: :lol: :lol:

 

[jfrabat]

Nah, I was looking for new trails, but they are all paved here! :lol:

Felipe

 

[redrooster]

There should be a vacuum diagram in the back of a Chilton or Haynes manual.

 

[jfrabat]

Red,

I found this diagram in my Chilton manual; it seems that there is a vacuum control, but also a cable? I gotta be reading something wrong here.... I know for a fact that the driver side's vent will open and close with a cable because it will open and open and close with the engine off, but the other one wont, and it seems in the diagram that one should be attached to the other.

Any suggestions?

Felipe