Blower on S90

anbran1 · Post by **anbran1** » 01 Jun 2013, 16:03

Just wondering why the air blower on the heater/AC system stops blowing for a short while...then comes on again?! ( I am not running it on Auto.) I can still hear the fan running...but no air coming out of the vents. I am curious if it's something to do with a "door" of some kind that's is closing off the air flow, then opens again and air full blast again?!

Maybe there is a vacuum system that operates the door and there is a leak?!

Any thoughts?

Post by **precopster** » 01 Jun 2013, 16:39

True there is a vacuum system. At the firewall check all connections and make sure the little one way check valves (small round black & white) aren't blocked and are only flowing in one direction.

Leaks can usually be heard after the engine is cut. There is a major vacuum item under the dash that can fail.

anbran1 · Post by **anbran1** » 01 Jun 2013, 18:22

Actually, now that I think of it...when I shut the engine off, I hear a sad "sigh", like the sound of the last bit of air in a balloon wheezing away...
Perhaps that's the symptom?!

anbran1 · Post by **anbran1** » 18 Jul 2013, 15:38

As I described, sometimes my blower works without any problem...then all of a sudden..Nothing! (It has stayed that way now for 2 hours of driving)
(Still can hear the fan running in all speeds, but not being directed anywhere...)

I pulled the panel off on the drivers side to view the vacuum servo that's visible. I pulled the line off of it and worked the controls on the dash. I didn't notice any suction on the tip of the line.

I was going to run out and buy a little vacuum pump to see if I can operate the servo by hand...hopefully learning that the servo is fine...and that it's the vacuum source that's problem...

I removed the panel on the psngr side and saw the vacuum "distributer" box (with several different colored tubes coming out of it... Is this the item that frequently fails?

How do I test this thing? Are they available? (...and what's it called?)

Post by **precopster** » 18 Jul 2013, 15:47

There are 2 small black and white one way check valves at the firewall.
First note which direction they're facing then remove and blow through them by mouth making sure that air flows in only one direction. If not this can be the source of the problem.

Post by **jimmy57** » 18 Jul 2013, 16:06

I would say you have a vacuum leak and the system is going to floor and defrost outlets and most people report no blower function but hear the noise in this situation. There can be multiple causes.
1. recirculation vaccum servo leaking
2. floor defrost vacuum servo leaking on floor position which is supplied with vaccum when the face vents on dash are opened
3. check valves or source hose leak in engine compartment
4. the electric vacuum solenoid valve bank has broken solder joint

You mention it doing this for 2 hours solid. That fits with the solenoid valve bank problem.
It is a gold metal and white plastic rectangular device with a wiring harness and a vacuum hose harness attached. It is located on the left side of the right hand footwell under the HVAC case.
Broken solder joint can usually be visually checked by looking at underside of the valve bank where the harness connector pins and conductor trails can be seen

The first three items on list usually exhibit when accelerating or climbing hills

anbran1 · Post by **anbran1** » 18 Jul 2013, 16:13

One of the check valves on the firewall, as you mention, blows both ways...

I guess it's safe to say, this is likely the problem?!

anbran1 · Post by **anbran1** » 18 Jul 2013, 16:19

Perhaps any vacuum check valve would work?! (as long as it fits)

Post by **precopster** » 18 Jul 2013, 17:24

Pretty much as long as it fits. The rubber diaphragm inside must have perished due to heat.

anbran1 · Post by **anbran1** » 19 Jul 2013, 20:40

Picked up a couple of these check valves at a wrecker...work fine.

I noticed the air is blowing again...but still, on occasion, the vent seems to close after about 20 mins of operation. I shut it off, then back on again...and it works. I am thinking that if a servo has a damaged diaphragm inside, it would be consistant...?! Perhaps that "electric vacuum solenoid " controller is to blame?!

Any ideas!?