Blower motor high speed problem

[Skip]

Yet another blower motor question.

My 94 Legacy has the normal AC system.
It's blower motor works on all four speeds -
rising in speed as it should.

Although "4" or high seems a bit lame in comparison to my other Subes.

but here is the kicker - when I push the defrost button
the fan goes into a much higher speed similar to my other cars.

This affects all speed positions.

The wiring diagram points to the ground point for the switch having some
corrosion.
(I am well versed in the resistor block, I have 12 Subarus- the switch has the ground point for the block.)

I believe the defrost position or AC system (in op when in defrost) is somehow providing the proper ground
for the switch/blower motor.

This is off the wall but
does anybody know where the ground point for the switch is?

(wiring dia. shows it separate from the ventilation control motors and AC system.)

Thanks for any help in this matter.

[Legacy777]

The reason defrost mode seems to kick the fan into a higher speed is because you have the same amount of volume going through a much smaller outlet, therefore velocity will increase if output is to remain the similar.

Do you have anyone near you with a first gen legacy that you could check and see how their fan speed is in comparison to yours?

[Skip]

Thanks Josh but you say
"because you have the same amount of volume going through a much smaller outlet",

Sorry, I don't think this is true.

The opening on the defrost vents when compared to the dash vent openings (I run with the pass. side closed)
is probably larger not much smaller.

It does not happen on the vent setting

I can hear the blower motor RPM increase

It does not do this on any of my other Subarus

I have no one with my gen Legacy to compare with.

Thanks for the thought though.

[Legacy777]

hmmm.....I know when I put it on defrost in my car it sounds like there's a hell of a lot more air blowing up through the defrost vents, then if it was just through the main vents.

You know I'm going to go figure out the area of the vents don't you

Either way, the opening is more restricted, therefore more noise, due to higher veloicity.

Are you sure you're just not hearing the air moving faster? Or are you actually hearing the motor spin faster?

Take the motor out of the housing. Have someone run through speeds & buttons while you hold the motor and see if speed changes.

I haven't looked at the wiring diagrams to see if the motor speed can any way be traced back to which button is depressed, rather then solely be related to the speed selector.

[Skip]

Okay Josh,
" the opening is more restricted"

about the restriction on the defrost ducts
I don't see Subaru "throttling" something as
important as the defrost vents. They do direct air
toward the windscreen but I doubt that they restrict
the opening as you say.

I do agree the opening may be narrowed a bit to aim the air flow
but not in so much as to provide the restriction you seem to think there is.

If I put the unit on "vent" and close all but one vent it
would simulate this.

If I was of the ilk I would pull the blower motor and
use a tachometer to see if it was indeed spinning faster.
I guess this is the only way to prove it.

I have looked at the wiring diagram in the FSM and
it shows no connection except possibly the ground point for the switch/resistor block.



As I ask in the first post,
does any one know where this ground point is?

[Legacy777]

I think you're missing my point. Subaru is not throttling anything. They may have actually designed the defrost to have a higher velocity air output then the other vents.

Look at it this way. You have a fan that can put out 100 cfm (made up numbers).

If you put the fan behind some duct work that is open at the other end and can flow more then the 100 cfm, you end up having very low air velocities through the duct.

However if you now stick some sort of nozzle at the end of that duct work and restrict the flow coming out, the air velocity going through that nozzle will increase because that is the only outlet in the system, and the surface area that air can flow through is much more reduced then the original duct.

This is how the HVAC system in your house works more or less.

Subaru may have designed the defrost outlets or nozzles to have a greater air velocity compared to the dash vents. This greater air velocity would ensure that the top portion of the windshield will see the defrost air as well.

Regardless, I'll look in the FSM and see if I can find where that ground point is.

[Brat4by4]

I have personally seen all of the HVAC vents recently... and I'd say the floor vents are more restricted than the defrost vents. But moot, I know.

[Skip]

Brat 4x4, thanks for the support

Josh,
I see your point and I did agree that there is some aiming and directing of the air.
This could lead to it sounding like it is moving more air.

You on the other hand fail to see my point
This is my first gen I Legacy but not my first Subaru.

I do have a gen II to compare to (03 VDC) and an 00 2.5 RS
and multiple GL series, even a Brat or three.
I do not think the defrost configuration changed all that much
that what I am hearing is being confused for the air simply going through
a set of nozzles designed to increase air flow.

You know me and my background well enough to know I would know
the difference - I hope.

In lieu of this discussion I did some more testing.
Up till now the speed increase has been notice while operating said vehicle.
I decided a more empirical way was to sit stopped and try it.

Thus - engine running vehicle sationary
Fan on "4", vent control on "Vent". Normal lame air output.
Push vent control to "Defrost" - the air flow diverts
to the dash and the AC comp engages - then about a second later the fan speed increases.
So I push "AC" - vents now have air moving much faster than when the experiment started.
Push "Vent" and the air flow remains at the higher rate.
I should have tested to see if the other speeds were also at an increased flow rate.

I know Subarus are notorious for ground faults so I am going to find the switch harness
and add an auxiliary ground to the ground point terminal.

I will dig in and find a solution to this situation - thanks for the
understanding and the help.

[professor]

My car does exactly as yours does...

you may be looking for a fault that does not exist, the situation may be normal

on the other hand, if you find something, let me know and I'll try it out also

[Legacy777]

Skip,

I'm not trying to ignore your point or anything like that, I've just never run across the issues you're describing. Looking solely at the wiring diagrams, there is no physical way blower motor speed can change by selecting different modes, only different fan speeds.

The only way output velocities can change is due to nozzle (vent) configurations and/or back pressure in the the ducting.

I will also mention that I have noticed air speed changes in the vents when I go between AC Max & AC. The reason for this is the flapper door being open/closed for fresh air. You might want to take a look at the flapper door and see if it's moving at all. If it is, that will play into how much air the blower can suck in.

Regarding the ground location. It's GB4, and it's located at the base of the radio area on the passenger side.

You see the small black wire where the bare metal is showing, just above the carpet & below the plastic portion of the dash

http://www.main.experiencetherave.com:8 ... P_2853.JPG

[Skip]

Josh,
In light of my recent tests and the post from the professor

I would simply say "Learn something everyday or the day is wasted"

I have a problem with your explanation due to the fresh air door not moving completely
like why does pushing the defrost or AC button cause it to move.

(I am familiar with the AC max operation and it's effects on flow rates)

To add to this I can feel air moving throuh the floor vents
when the "off" button is pushed

but I will look at it to rule out the possibility-

Thanks for the info on the ground point location.

There is a possibility the ground path is shared by other hvac
components

namely the AC system.



(sorry I couldn't load your link
my DSL is having problems resolving your host)

[Legacy777]

I'm not sure if the fresh air door moves or not. That's what I was suggesting you check. If it does move, that might help explain things.

Yeah it's normal for air to move through the floor vents when the system is off. The owner's manual mentions it.
(try the links below)

https://www.main.experiencetherave.com/ ... ns/044.jpg
https://www.main.experiencetherave.com/ ... ns/045.jpg

This is the pic I posted above,
https://www.main.experiencetherave.com/ ... P_2853.JPG

[Skip]

Josh,
As always thanks for the links, you have done a fine job sir.

I think you missed my point - I made reference to the air moving when
the system is in the "off" position in answer to the question on the fresh air door
being open or closed.
I read this in the manual and thought it pertinent.

Please excuse my fox paw.
The door is moving as it should.

My search for the ground point continues
as my car is a bit more "together"
than the one pictured.

Thanks again for your time.

[illnastyimpreza]

ok so my blower motor went.....then my heater core decided to die. now I'm freezing my ass off!

anyone got a link to replacing them??
thanks!

btw...will WRX heatercore and blower work?

[islander]

I know this is an old post but you may still having the same problem. I had the same problem with my 94 Legacy (141k miles)and decided to attack it this weekend. From previous look around the blower area I knew there was a lot of dirt in the neighborhood and thought that since there was so much dirt (lint) there the blower being a fan would be in the same conditions.
I removed the passenger seat to help me move around and have space for the tools. Then removed the glove compartment and the bar where it is attached to. Removed the three bolt from the blower motor and voila, it was dirt as hell as the sorroundings.
I cleaned everything around and inside where it seats with a vacume cleaner and a mix of water and light degreaser. Removed the fan from the motor and cleaned it with the light degreaser and several brushes. Now it was white as it came from the factory.
Installed every thing but the glove compartment and it came more powerfull than before but still have some small leak betweek the blower and the housing where it doesn't seat very well but I will later add some kind of sponge like gasket material to fix that.

Next step will be to clean the evaporator. I intruduced my finger in the opening of its housing and noticed it was dirty too and scratched the dirt that I could in the process.

Hope this help you or anyone else that come here with the same problem.

Arturo C.

[tossem]

I have a 93 Legacy wagon and this weekend driving on a hot day noticed that on full blast it was not really keeping up (lame as you put it). I think once it starts cooling off I will see how maybe I may be able to add a cabin filter around the input (even if it has to come from another make) in order to keep dust and debree being sucked into the system. The fan works on all (4) settings as well, that is a difference in fan speeds. I was wondering if perhaps one of the fans from a newer sub had been tried before, allowing for more air flow. I was given a short lift from a friend who drives a Passat (99) and noticed it was blowing much colder than my sub. I was satisifed later when the sun went down and it was blowing real cold, but was wondering why it did not keep up when the sun was out. On another point, I just bought the 6 book manual from a 90 and was wondering if it was worth buying the updated single volume update for the 93? thanks

[ffprz]

I know this is an old post but I hope someone can help. I want to start off by saying I'm new to subarus and don't know them that well. My mechanical skills are very limited. The blower only works on 3 and 4. Do I need an new blower or unit? I have to replace my heater core so I thought it would be a good idea to take care of this problem as well.

[mike-tracy]

Welcome ffprz! This is a pretty common problem

(Edit: the experts below have spoken, its prob the resistor on the fan box, not the solder welds on the fan control's board as i suggested)

Here's a long thread about this problem: http://bbs.legacycentral.org/viewtopic.php?f=10&t=1142

[rallyak]

If it only works on 3 and 4, wouldn't it be the fan resistors?

[Legacy777]

I would tend to agree with Charles, it kind of sounds like the resistor pack in the blower motor box.

You can see the blower motor resistor pack in this picture over near the removed glove box and in these pictures of the AC evaporator box.

http://main.experiencetherave.com/subar ... P_3461.JPG

http://main.experiencetherave.com/subaru/images/acevap/

[ffprz]

Thank you so much for the advice. I was low on funds this weekend so I picked up a resistor at the junk yard and it worked! I have already started taking apart the dash. My question is since I am already replacing the resistor and heater core what else should I replace or do maintenance on? So far taking apart the dash has been a pain in the ass and I don't want to do this anytime soon.

[Legacy777]

I'm not sure you can get access to it without taking the AC evaporator box out, but they tend to collect leaves and junk so you can clean that out. You may be able to remove the blower motor from the bottom and take a look at how clean it is.

Grease the control arms for the HVAC mode selector box. Mine has developed a little squeak and I had my dash out previously. So I'll probably live with the squeak for the time being.