Root cause insight into the common BMW blower motor resistor failures

Page 6 of 14  
On 03/21/2013 06:59 AM, Nate Nagel wrote:


retard.

don't lecture me on electronics nate.

if you don't know what the FUCK you're doing and don't know how to use a dvm.
--
fact check required

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 03/21/2013 10:41 AM, jim beam wrote:

<https://groups.google.com/group/rec.autos.tech/msg/1870e822d74b0a5c?dmode=source&output=gplain&noredirect&pli=1
link times out?

ooh, or what? ITG gonna kick my ass? Sorry, I'm more interested in helping the OP than your delicate little feelers.

WTF is that supposed to mean?
OP can dissect the thing all he wants but it doesn't do him a damn bit of good to know *what* has failed unless he knows *why* it failed.
nate
--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
jim beam wrote:

Sure it can, if you're nothing more than a low grade grease monkey.

Your checks always bounce.
--

Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 21 Mar 2013 03:55:47 -0700, the will wrote:

This is an interesting approach, given that the vast majority of bimmer owners do NOT replace the blower motor - they replace the FSU.
While the blower motor replacement procedure is a major PITA, one 'can' test the leads from the FSU harness connector pins #5 and #1 which are power and ground respectively to the blower motor.
Again, we don't have a circuit diagram, but it has been said that the blower motor takes about 6 amps (variously, depending on the speed) but it would take a test jig to test that in operation.
To my knowledge, nobody has created that test jig (although I know of only one attempt, which failed): http://www.bimmerfest.com/forums/showthread.php?tg8534&highlight=fsu
It's easy enough to test the resistance of the blower motor though, and those results have come out at about 0.4 to 0.6 ohms.
It would be expensive to change a blower motor on a whim, so, how would YOU suggest the blower motor be tested in situ?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Static resistance doesn't tell you anything, but operating current measured with a DMM would tell you a lot.

I've never tested one, but I put a drop of turbine oil on the motor bearings every five years or so. I do the same on the window and seat motors too.
I'd imagine if you listen carefully and have good hearing you can tell if the motor is binding at all, but many people do not. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 21 Mar 2013 11:45:54 -0400, Scott Dorsey wrote:

It 'can' be done, but would require a test jig inserted inline as the FSU is deeply ensconced under the dash while the blower motor is even more deeply so.

While that preventive work might be prudent, the sheer effort to remove the entire dash simply to access the blower motor would be problematic.
Still, if the problem is that the blower motor is merely using more current as it gets older, why wouldn't a NEW FSU burn up within a few weeks of insertion?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 03/21/2013 06:04 PM, Bimmer Owner wrote:

If the unit is near its limits it might just get very hot and parts start aging very fast -> semiconductors will just fail after a little while. The new unit should fail sooner than the old one but who knows who soon, maybe after a few years. Peugeot's ( and Citroen) used just one huge pnp darlington which failed quite often , it was working too near its operating limits.
(just my 2 cents) ismo
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I don't know the wiring diagram on that particular model, so I don't know where you would need to break in to measure just the current of the blower without anything else. But it does not seem terribly insurmountable, especially seeing that BMW is very good about breaking everything out into connectors all over.

Well, that's partly why I drive a 2002 and an E28, everything is much easier to get to.

You would expect that, indeed. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Just measure the battery current with and without the blower running.
Turn every thing else off.
QED
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 21 Mar 2013 16:59:01 -0400, tm wrote:

That's a pretty good idea.
Of course, it's impossible to turn everything off, as the computer won't go to sleep for 16 minutes after the car is shut and armed, but, still - with the blower consuming something like 5 or 6 amps, we should be able to measure at least that.
The problem, even with the car's additional electronics powered up, is HOW MUCH of a difference are we expecting between an older blower motor current draw and a new one?
Are we looking for a 1 amp difference, for example?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Just put your ammeter into the heater blower fuse connector and you get the current of the blower motor.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 03/21/2013 05:01 PM, snipped-for-privacy@snyder.on.ca wrote:

what he said.
--
fact check required

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 21 Mar 2013 20:01:20 -0400, clare wrote:

That's an interesting idea.

The fuse for the blower motor is called the "infamous F76" for a reason. http://bimmerfest.com/forums/showthread.php?tg4612
It's a 40 amp fuse under the glovebox but it's in a really inaccessible spot; however, it's right side up, so, the wires going INTO it are visible from the tips of your feet under the glove box.
So that's a possibility; but you'd have to cut the wires.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 03/21/2013 09:31 PM, Bimmer Owner wrote:

you don't want to try and use a 10/20A meter in the slot of a 40A fuse. you probably already know that, but just saying.

--
fact check required

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Fri, 22 Mar 2013 04:31:00 +0000 (UTC), Bimmer Owner

Why would you have to cut the wires???? Simply remove the fuse and connect the ammeter. You guys make your lives so difficult
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mar 22, 3:04 pm, snipped-for-privacy@snyder.on.ca wrote:

It's kind of amazing the fuse is 40 amps, no? I mean a 1 hp motor draws ~1500W And this heater blower is 480W? Seems like a lot to me.....
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 03/22/2013 12:43 PM, snipped-for-privacy@optonline.net wrote:

in this thread it's been said it draws 6A running. x 12V, that's 72W.
but the reason you have 40A is you have very high current start-up transients. on a cold day with a gale blowing outside the car, and some snow in the system, you could be into the 30's without too much problem. so you need an amperage that will still blow in the event of short circuit, but which will tolerate the above.
--
fact check required

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@snyder.on.ca wrote:

Take a blown fuse and use it for a test connector with a cheap 50-0-50A meter. Then you can just plug it in in place of the fuse to make the test. You won't even have to worry about the polarity. You can use a high current shunt, & a digital meter if you want more accuracy.
--

Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 23 Mar 2013 22:27:41 -0400, "Michael A. Terrell"

Or just get the special tester that is made to plug into the fuseblock. Autel makes the MX101 and 201 (10 amp and 20 amp) units for the lighter duty stuff.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@snyder.on.ca wrote:

Is that cheaper than roll your own?
--

Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.