1990 740 GL - No air from blower, with any setting

You've got a vacuum leak somewhere, find the source of that hiss and you will probably find your problem.

From what I found... Nothing... Everything seems operational. So I'm guessing an obstruction someplace.

Any 'best practice' ways of going about looking for this possibilty?

Charlie

Do you have a Haynes manual for the car? It should show the layout of the ventilation system. One of the flaps somewhere must not be opening, I don't see how any foreign object large enough to cause that could get in there.

No manual, well I have the Chilton®. Wow does that guide ever suck!

Think I need to just pull it out and tear in? Seems like a ton of effort, but it's getting COLD out!

Chilton manuals are worthless, they try to cover too many cars in one book. Haynes isn't perfect but it's much better. If I think about it I'll look in my manual when I'm home.

I bought this car 3rd hand. So I only have the history the prior owner gave, very little.

The cowl (is that the term for the area the windshield wipers are in?) would seem to have a screen under it. That screen has a small (mouse?) hole in it. While removing / replacing the blower motor, I could see no signs of foreign items.

Would it be safe to 'snake' a piece of wire down through the cowl? I do not wish to puncture anything, and I'm unsure of the exact location of the heater core. Is this even wise?

This link may be of interest...

If there's an archive of this newsgroup you might go back about 3-4 years when I had similar problems with a 760GL: winter was almost upon me and I could hear the fan motor working hard but no air was coming out!

Here's my advice (because it's what I found was the problem with mine):

Remove the blower motor and reach into the opening and feel to your left for the evaporator (a fine grille of fins that are part of the air conditioner). It should feel like the face of your radiator but it may feel like a solid rubbery wall.

At the point I'm describing the air from the fan is expected to pass through the evaporator and cooled/dried. In my case we surmised that the previous owner added some leak-stopping substance to the pressurized AC system and it leaked out from a hole in the evaporator and coated the fins. Over time dirt and general crud collected on the sticky surface (no pre-filter on the air intake in these older models) and eventually gummed the whole thing shut.

In my case I simply accepted that I wouldn't have AC and wrenched the offending part out (and many other ancillary AC components that were not needed) and the air blew through the duct system like a gale! Eureka!

The thread from trying to diagnose this problem was at least 35 posts. I checked fuses, vacuum lines, wiring, solenoids, electronics with a voltmeter, etc. etc.. My first assumption was that some vacuum-controlled gate was stuck shut but after I pulled out the evaporator everything else worked flawlessly!

I still have a pile of details from the 760 and suspect that, while there may be positional differences, most of the components will be the same. Let me know if you'd like me to email you the whole bundle but first check that evaporator!

Good luck, blurp

Thanks, that was informational. It also seems to fit my issue. I was able to view the evaporator when replacing the blower, but at that point I was only looking for the obvious squirrel nest or other debris and remnants.

I have a little access panel between the blower and the evaporator, that when removed the air comes out at the expected high rate. Of course it's just the outside air I believe, so just leaving that off is no help :)

Thanks for the heads up on the spin direction. I will triple check this. The 'original' two connecter plug has been replaced with crimp connectors and spade plugs to connect the motor. I'm assuming some one did a quick/cheap fix on the blower in the past. I just plugged the new one in 'same as it came off', but who's to say that was correct...

Well after an afternoon with a 2 foot section of 5/8 heater hose connected to the shop vac. A 4 foot section of fish tank air line tubing connected to an air gun(Use this with care! It will flip around like crazy.) I've blown and/or sucked all the vents possible, The air flows great now. Sweet.

Thanks to all who took the time to consider my problem and provide their input and experience. It all helped in one way or another.

Now to find out why the underside of the trunk carpet gets so wet. (But I'll start a new thread for that, if it comes to it)

Thanks again.

Charlie

Been there, done that. Look at the taillights, particularly the foam gaskets around them.