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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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  #1  
Old 08-23-2010, 01:53 PM
CPBIII CPBIII is offline
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How to check blower motor resistor

I recently (3-4 months back) replaced the blower motor resistor in my 2002 325i. This morning I get in the car and no fan.

I called the dealer and he said there is a warranty on the resistor pack. But for them to honor the warrant they would have to check the resistor pack. Fair enough, except that they want to charge me $125.00 if the resistor tests good.

How can I check this resistor ahead of time (evidently it must be installed to check) so I can avoid a $125 check-out fee?

(I am plumb with digital multimeters and O-scopes if that will help.)

Thanks,

Chris Breidenbaugh
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  #2  
Old 08-23-2010, 02:58 PM
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Tangent Tangent is offline
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Turn the fan speed up to maximum manually. If the fan starts to run, that's a pretty sure sign that the FSR failed. $125 seems rather steep for just checking considering that $63 and half an hour of your time will get you a new FSR if you DIY it...
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  #3  
Old 08-23-2010, 04:29 PM
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G. P. Burdell G. P. Burdell is offline
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You can use your multimeter do some diagnostics at the plug that connects to the final stage unit. There should be a variable control voltage coming from the HVAC control panel - the voltage goes up as you increase the fan speed on the control panel. The plug should also have a wire that's switched 12V from the blower relay. You can even jump a couple of wires in the connector to force the blower to run at full speed. If you can access the blower relay, you can also make sure that it is functioning properly. If the relay is working and there's switched and control voltage at the plug and you can get force the blower to run, then the final stage unit is probably the culprit.

If you have the Bentley repair manual, you may find an electrical diagram with the pinouts for the connector.

I learned these things on my old E36, which ate a couple of these final stage units - I haven't yet had the privilege of having to do the same diagnosis on my current car.
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  #4  
Old 08-26-2010, 03:43 PM
CPBIII CPBIII is offline
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Thanks for the reply.

I do have a bentley manual and I found reference for the blower motor resistor. But it is only showing the AC and Heating control module. I don't see the resistor called out.

I checked the 5 and 50 amp fuses, they both were nominal.

I guess the next step is to get under the dash....
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  #5  
Old 09-19-2010, 09:29 AM
CPBIII CPBIII is offline
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So, refusing to beleive that the FSR was the culprit, I dug in the blower motor. After disassembling firewall to get at motor, I was horrified to find that the motor was now working! I stripped alittle bit of insulation from the motor wires, and checked the voltage. Everything appeared nominal there. Max voltage was around 6 volts.

After driving the car for 3 days the motor has died again. So it's tear the firewall apart agian to get at the motor. This time nothing. The motor has died and remained so. I have removed the FSR and will replace that (again).

The one in the car now came from the dealer.

sitronic 29420000002 46 09

Wish there was a way to check this thing.... back under the dash I go...

OK so I re-connect the battery, and start loking for juice. With fan on high and grounded to the door hinge, I am seeing 12 volts on the green and yellow with greeen strip. The small blue wire is at 8 volts. The brown and tan wires are both <1. As I am rotating the FSR in my hand to check the last wire, the fan suddenly starts blowing. As I "jiggle" the connection, the fan starts going on and off. Hmmm bad connection. This looks like a fully potted unit. I'm going to see if I can "tighten up" the plug connections.

OK, found the connector appears burnt. This appears to be the ground plug.

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So I took so solvent to it and the smallest phillips screwdriver I could find to clean out the inside.

Hooked it up, but I was still getting intermittent operation.

My final solution:

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Yep, a small piece of cardboard. This seems to have done the job. No matter how I move or shake the FSR I cannot get it to miss.

If this fails at some further point (like I torch the car) I'll pass that on too.
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  #6  
Old 09-19-2010, 08:31 PM
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Solidjake Solidjake is offline
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Nice repair. I've worked on a few E46's a lot of them have burnt sockets like that. It's terrible.
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  #7  
Old 09-27-2010, 08:14 AM
CPBIII CPBIII is offline
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I drove the car to Cleveland and back (from Baltimore area) last week. No issues with the blower.
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  #8  
Old 02-18-2011, 01:10 PM
CPBIII CPBIII is offline
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As an update to this repair.

The cardboard fix has died this week. It is still a matter of a bad connection though. If I move the connection around, the fan will blow.

I'm hesitant to start prying on the female terminals to make them more snug. It does not look like fun to replace that terminal, should I really bugger it up.

I might try a small piece of wood this time. Something more durable than cardboard.
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  #9  
Old 02-18-2011, 03:17 PM
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bluebee bluebee is offline
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Over in the E39 side of the house, we've ripped apart a few FSU/FSRs.

We've concluded the GKR ones are the worst; the Sitronic are the best.

But, beware of the branding as up to four (yes, four) brand names are on FSUs with most having at least three (e.g., valeo, siemens, bmw, bosch, hella, etc.)

We've also made an attempt at measuring them.
- Understanding and TESTING the Final Stage Unit (FSU/FSR)

See also:
- FAN CONTROL GOES HAYWIRE: poorly ventilated final stage resistor/final stage unit (FSR/FSU) modules that are practically sure to go haywire due to poor heat-sink design (1) (2) (3) (4) (5) (6) (7) (8) ... Autopsy (1) (2) often causing the battery to drain overnight (1) (2) (3) & how to isolate and replace the blower motor (1) (2) (3)

If there was one thread to read above all the rest with respect to testing them, it might be this one:
- failed blower resistor (final stage resistor) not really dead

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  #10  
Old 02-18-2011, 03:19 PM
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bluebee bluebee is offline
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I just checked the recommendations ...

Recommended:
- Sitronic/Bosch

Not recommended:
- GKR
- Behr
- Valeo,
- Siemens

Certainly not recommended:
- Meyle
- Hella
- Uro
- Denso
- Power Pro
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  #11  
Old 02-18-2011, 03:57 PM
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marinekilz marinekilz is offline
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Quote:
Originally Posted by CPBIII View Post
As an update to this repair.

The cardboard fix has died this week. It is still a matter of a bad connection though. If I move the connection around, the fan will blow.

I'm hesitant to start prying on the female terminals to make them more snug. It does not look like fun to replace that terminal, should I really bugger it up.

I might try a small piece of wood this time. Something more durable than cardboard.
If thew connector is burnt........read the part number off of it and order a new one. Can't be more then 10-20 bucks from the dealer. you can also fix the pins on the connector when you remove them from the old connector. Or just replace all the pins as well.
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  #12  
Old 02-19-2011, 08:04 AM
Mark@EAC Mark@EAC is offline
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I would certainly consider replacing the connector or splicing in one from a donor car or something. If the thing is already melted the last thing you want to try to repair it with is cardboard, that could be a fire hazard.
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  #13  
Old 02-19-2011, 08:49 AM
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G. P. Burdell G. P. Burdell is offline
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Quote:
Originally Posted by Mark@EACTuning View Post
I would certainly consider replacing the connector or splicing in one from a donor car or something. If the thing is already melted the last thing you want to try to repair it with is cardboard, that could be a fire hazard.
Seconded. If the ground contact and the connector have been damaged by heat, then the whole thing needs to be replaced - just like the tail light connectors that suffer heat damage due to insufficient grounding.

See if you can read a part number off of the old connector, and take that part number to your local dealer. They can also sell you the round socket contacts that crimp onto each wire - make sure to get the right sized contacts for the wires you will be working with. It looks from your photo as if there are four 14- or 16-gauge wires and one 18- or 22-gauge wire. If that's the case, there would be different contacts for these two size ranges. I always like to get a few extras of each size, as well as more than one connector, in case something gets messed up.

All that's required is to cut off the old connector, strip the insulation off of the wire ends, crimp the new socket contacts onto the wires, and insert them into the new connector. An open-barrel crimp tool is fairly inexpensive and best suited to the contacts you'll be working with. The smaller tabs on the contacts curl around the wire strands, and the larger tabs grab the wire insulation.

Give each crimp a gentle tug to make sure it's secure. Check and double check the wire colors before inserting the sockets into the new connector. Each socket should lock into the connector with an audible click. Tug gently on the wire to make sure it is locked in place.

I would do this work with the battery disconnected, just to be on the safe side.
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  #14  
Old 02-23-2011, 09:16 AM
CPBIII CPBIII is offline
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You all are spot on about the connector. It will have to be replaced.

As the closest dealer is a half hour away, I stuck a wire tie on it till I can get up there.

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