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DagNabbit! Heater blower is toast! (to be archived)
Posted 30 January 2002 - 01:20 PM
It later tried to come back to life, but teh smell of electrical components smoking made me turn it off. Not a very nice ride home, 35 miles at temps well below freezing. Luckily I was able to go back to my company garage (heated) and "pack" the car full of warm air. I could see my breath again abouot half way home.
Anyhoo.. I found the resistor thingies, and yes they were looking bad. I putzed around with them a little and got most switch positions to work again, but I really only have two or three speeds left.
Who cares. I thought it was all fixed by then, and I tested the unit outside of the chamber..
No luck. Intermittent contact, variable speed and SMOKE. Not good.
So I opened up the blower motor, and noticed that one brush was missing and the other one was worn to the braided wire. Time for new brushes.. .but where to get them? I will try my local auto parts store to see what they have on the shelf. Maybe I can adapt something that's "close enough" right out of the box.
Damn. These troubles never end with an old car. I *almost* miss the days when I had a free brand new BMW for a year, including free gasoline. (thanks dad). BMW? Ok, I repent, it was a lame yuppie-mobile, but hey it was free. (long story). Besides I said "almost". I'd still choose my Subaru over any BMW, unless I was allowed to sell the beemer right away. Then I'd use the money to buy a Sube. :-)
Anyway.. just thought I'd vent.. and in case someone else is having the same problem, or it hits you some day in the future.. I'll post my results. I'm trying not to buy a new blower. Taking the old one apart is super simple, and so would be brush replacement, if only I could find some.
If I find a direct match, I'll let you know what car they belong to.
I can probably go in the shop and look for myself, I am a pretty good customer..I show my face there and I get 20% off of most everything... LOL.. maybe it's my face and not my previous purchases.. maybe they just feel sorry for me :-)
Posted 30 January 2002 - 01:47 PM
You may also condider an aftermarket "auxilery"-type heater temporarily. I can't imagine its much fun driving around January in your part of the globe without heat!!
Yes, and BMW's are waaaaay overrated...
Good Luck, John
Posted 30 January 2002 - 04:14 PM
Posted 30 January 2002 - 05:36 PM
The selector switch is probably ok. It is the relay/resister module that is probably the culprit.
You can test the blower motor by bypassing the switch. (applying juice to the pos terminal, grounding the neg). I can't help you on wire colors being at work now, but the motors themselves are very simple. Maybe as few as two leads.
If the motor checks out, I would go for the resister next.
Also, don't forget to look at the fuse for this circuit as part of your diagnosis.
Good Luck, John
Posted 30 January 2002 - 06:56 PM
The block is for controling only the first three speeds -- #4 by passes the resistor block.
Relay controls all operations.
The blocks go toast @ about 75 kmi, generally starts with no.1 then 2 then all you have is high.
But you do not need to test it to test the blower- speed 4 does that
Now, if it will not run on any speed, barring Jan situ. it could be the blower relay.
To check and or replace the resistor block- look under the glove box toward the fire wall and up
The resistors sit in the air stream of the heater duct and the unit is held with three screws
Two of which are obvious the third is one one of the motor mount screws.
The wire colors are blue, blue/blk, blue/yel and blue/white.
Last time I checked the dealer wanted about 60 bucks for a new one.
The blower switches themselves do go bad but it is more likely the resistor block.
Good luck and I wish Shawn would put this in the USRM.
Posted 30 January 2002 - 07:36 PM
Posted 30 January 2002 - 11:07 PM
Posted 31 January 2002 - 12:06 AM
Posted 31 January 2002 - 02:25 AM
(also minimal heat output)
Posted 31 January 2002 - 02:42 AM
Brushes were toast.
Posted 31 January 2002 - 06:52 AM
I did not find the correct brushes, and not even any that would slip in right out of the box.
I ended up buying a set of 4 Bosch starter brushes, I figured I could use a backup pair if something went wrong with the first attempt.
The original brushes were 7mm by 7mm in profile, lenght unknown (for obvious reasons :-)
The Bosh starter brushes were 7mm by 9mm or so. I just filed them to 7mm from two sides, and also shortened them a couple of mm. Then I filed a slight round curve at the tip of them so they'd wear in faster. Then I soldered them in place.
A quick test revealed that it was a success at first try.
Then it was time to look at the resistors... there are three coiled wire resistors on the resistor block, and the middle one was a true goner. What little good wiore was left of it, I straightened and scraped it clean and shiny, and did the same to the opposite side, then tied the ends together. Did not use solder there, I guess it would not hold if the wires get hot enough to need external cooling from the fan. I noticed that one other resistor coil was a bit shabby looking too at teh end, so I shortened it a bit and did the same cut&tie trick to it. I eliminated maybe 1-2 coil rounds.
I realize that it's just a matter of time until the next weakest spot on the resistor goes bad, but at least I bought myself some extra time. I can now start looking for a replacement without panicking.
Result: I have regained all 4 speeds, 2 and 3 are almost identical speed (due to me having to eliminate one resistor) and 4th is real strong. It did smell a little at first, but it soon stopped and everything is now back to normal.
Oh BTW I also put some spray vaseline to the bushings that hold the fan axle shaft ends.
Plus your regular "clean it with compressed air" procedure.
All is well now. It was easy. Hope this helps someone.
Posted 31 January 2002 - 08:52 AM
Posted 31 January 2002 - 10:16 AM
Does anyone happen to know if there are replacement/substitute resisters available to do a repair on the module? Or even values on the resisters?
I asked this a while back, and no one responded. If this info could be determined, it shouldn't be too hard to locate parts, and document a standard procedure for repairing this component.
Posted 31 January 2002 - 10:47 AM
Posted 31 January 2002 - 12:01 PM
Anyway.. I would like to know this too.. maybe if I used some heavy duty porceline resistors..
Oh, I once picked up a Toyota instrument panel dimmer switch, it was also the same type, (coiled resistor wire) mostly embedded in insulating material. This was great for all kinds of purposes, I use it to lower the current going to my VW's 6V wiper motor in a 12V system. It is very tough and can handle lots of load. And what's best.. it has no "steps", you can set it to whatever speed you like. Looked tough too, and it was pretty big, not sure if it would fit in the stock location, replacing the original switch. I may try it next time my resistors go bad.
Posted 31 January 2002 - 12:46 PM
It gave a source (DigiKey) and exact part numbers to build your own resistor pack that would conservatively last three or four vehicle life-times.
I'm at work now (on lunch break) - but I may have saved what I posted to my hard drive at home because of all the work that went into it, figuring someone would need it repeated some day. Or perhaps someone can find it in the archives and point to it - if not, I'll see if I can dig it up and post it tonight.
If you would build this pack, it would not fit in the original factory location because of its physical size - that's the trade-off - you can choose the marginal factory ones that will periodically fail, or build this unit that will last forever. It is so over-designed that it will survive the load in ambient air (i.e., would not need to be in the fan air flow). It is properly designed - wattage and resistance values are propely calculated, with very hefty design safety factor on the wattage.
The resistors I chose are inexpensive square rectangular body ones. Not the most efficient space-wise, but an order of magnitude cheaper than more compact ones, and they are readily available in the resistance values needed - which the more expensive compact ones are not available in except by special order which would drive the price up even further.
Don't bother with Radio Shack on these resistors - they have the type, but nothing near the values and wattage you need. DigiKey has everyone beat for price and availability.
Posted 31 January 2002 - 12:50 PM
Sounds like you have your motor working. FWIW, for you U.S. guys, I replaced the fan motor in my '86 Subaru several years ago (before I worked in the brush factory) - my blower motor brushes had worn out. I ended up ordering an exact fit replacement motor thru NAPA for about $30. It's still working fine many years later (price is probably higher now if still available).
Posted 31 January 2002 - 12:59 PM
Just take the old brush stub to your local auto electric shop, they should be able to find you some for cheap.
Posted 31 January 2002 - 03:59 PM
I just knew I wasn't the only nut who would go to such legnths...can't wait to your design..
I'll have to check out the supplier you mention. I usually deal with Mouser. They are also not too bad in most respects (if you havn't dealt with them yet).
Posted 31 January 2002 - 04:28 PM
For those who don't know about resistors and are considering doing this repair themselves heres some info: Reisistors typically come in a standard set of values measured in Ohms. They are also rated according to their accuracy. That is, 10, 5, 1% tolerance values are common. Another resistor spec is Wattage or Power Handling ability (their ability to dissapate power in the form of heat). If you try to pump a lot of electrical current through a resistor you will need a higher Wattage resistor. Resistors typically come in with various power ratings: 1/4, 1/2, 1, & 5 Watt varieties are the most common. I've found that there seems to be less of a selection of resistance values as you climb up the power handling scale. I'm guessing the resistor Wattage we seek is probably at least a 1 Watt or possibly 5 Watt. I'm hoping its not any higher than that as they can get quite large physically. In the higher Wattage range they can be round or rectangular shaped. I imagine if you have a high enough Wattage you won't have to mount the resistor block within the air duct.
Yes, Digitech has a nice selection of high wattage resistors. If your lucky enough to have a decent electronic supply store nearby you can probably get them there. Radio Shack is a long shot.
Posted 31 January 2002 - 06:05 PM
Posted 31 January 2002 - 08:24 PM
Checked back to the oldest page still logged and it's about the beginning of this month. Unless there's some way to retrieve December's posts, it's gone forever. Dummy me--I should have had the thread archived.
Posted 01 February 2002 - 04:25 AM
Posted 01 February 2002 - 08:38 AM
Posted 01 February 2002 - 10:34 AM
I went to an electrinics supply store, they have a pretty good selection of everything. I talked with one of the clerks and a customer who knows cars and electronics, and together we tried to guess the current draw of the stock blower motor. Based on some calculations, they recommended a variety of 50 Watt resistors. I chose two, 1.5 ohm and 2.2 ohm. In series, they would give me third option naturally, 3.7 ohms. (damn I'm good at math).
So this should cover speeds 1, 2, and 3. Fourth speed is direct feed with no resistor, like normally.
I haven't tested them yet, I will report back later.
These resistors are about the size of my thumb (thickness and lenght) so making them fit in the stock recess where the coil resistors used to be, will be a challenge. They would also require some kind of a heat sink to achieve 50W, and if I can place them in the blower airstream like the stock resistors, all the better.
I'm going to see if they'd have enough room to squeeze into the stock location vertically, with an aluminum bar bolted in between for heat sink. Maybe i will need to just attach long wires on them and feed the whole "bait" into the heater channel (between the blower and the heater core, naturally..) then just solder the wires to the old resistor block terminals.
Will be interesting to see how hot they get. I wish they didn't need any extra heat sink.. it would save space. These things are built inside an aluminum tunnel, the outside is a bit ribbed so that it would cool better.
Sorry, no pictures available yet.
Stay tuned, I'm going to the garage. :-)
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