Final Stage Resistor fix DIY

[jimparker65]

Not so easy on a RHD car. Pedals are in the way. I've managed to extract the plug from the FSU but cannot see enough to see what is holding the FSU in place. Any clues please or a photograph of the tab etc that must be holding it. By the way the FSU costs about $400 in the UK.

[x555a]

Originally Posted by jimparker65

Not so easy on a RHD car. Pedals are in the way. I've managed to extract the plug from the FSU but cannot see enough to see what is holding the FSU in place. Any clues please or a photograph of the tab etc that must be holding it. By the way the FSU costs about $400 in the UK.

£400 I'ts an fsr and it costs about £45.Looky here.... Final Stage Resistor : C3BMW Ltd

[rooroo]

Originally Posted by HEISING

If you find that your blower motor is pulsing or randomly coming on after your vehicle is turned off, this may be your answer. If your blower motor is on full all the time, this fix may not work as the semiconductors may be shorted at this point. Remove the FSR from your vehicle. Carefully remove the potting material in the corner shown. Go slowly because you don't want to damage the circuit board below. The potting material is soft so this process is relatively easy. You will see two sets of three legs when you have successfully removed this material. To see the board and these pins easier, you may want to put some contact cleaner on the end of a Q-Tip and wipe the board to remove access "small bits" of loose potting material. In most cases, the solder will be broken around these pins connecting to the circuit board causing irratic operation, "blower motor doing it's own thing." Carefully resolder these pins. Make sure you don't bridge any pins with solder. If you do bridge the pins, remove the access solder and try again. Run a small jewelers screw driver between the pins to make sure there are no solder bridges. Once this is done, you are ready to try it. You can see my FSR below. This is what I have done and it now works great. You will see some larger solder connections, I have done this to prevent future problems.
"IF YOU DO THIS PROCESS, YOU ARE DOING IT AT YOUR OWN RISK."
IF YOU DO NOT FEEL CONFIDENT DOING THIS PROCESS, "DON'T DO IT!"


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edit: By chance I came across this thread, I believe every E53 owner should know about this!

Thank you HEISING!!!!

This worked for me and my fan is blowing again...

symptoms: Front vents quit blowing air... everything else seemed to be in order. I could hear the ac trying to work if I hit the "MAX AC" button but no air flow. If I tried turning on the fan, absolutely nothing happened. Rear vents worked BTW.

This is worth a try for anybody that needs to replace the FSR.
I happen to have a soldering iron and have almost no experience with it. (I use it as a wood burning tool) I have never soldered on a circuit-board before.
The hard/tedious part was removing the potting material and not knowing how deep to dig without scratching the green board.
I used a precision flathead screwdriver to remove the bulk and shaved down a popsicle stick to the size of the flathead to safely remove the remainder. Q-tip dipped in alcohol to clean and better expose the pins and circuit board.


It is mentioned in the how-to, but I'll say it again... You don't need to remove the Glove-box to access the FSR. Just the carpeted part where the outlet is attached and the black plastic piece under the glove box where the foot-well light is attached.

Thank you, thank you, thank you!!

[greggw2gs]

I just replaced mine last week for $55 plus 1 1/2 hours of beer drinking work. I would recommend just replacing the unit if you have the money. Getting access to this resistor isn't the easiest thing to do so I wouldn't want to have to go in there again...

[greggw2gs]

Its been a year and still works like new!!!

[Jordo]

I just noticed my rear vents not working. I thought I noticed it getting weaker, but could have been in my head. Does this part control the rear fan motor?

Thanks!

[HEISING]

This fsr does not effect your rear fan.

Hey guys, glad to see people benefitting from the the DIY! Such an easy fix too. Eventually your new fsr will do the same thing "greggw2gs" so better stock up on the beer Hope you saved the old one so you have something to swap in.

[greggw2gs]

Wow I hope the new one lasts long enough to make it worthwhile... I did save the old one but I can't see myself putting that old one back in...

[HEISING]

Originally Posted by greggw2gs

Wow I hope the new one lasts long enough to make it worthwhile... I did save the old one but I can't see myself putting that old one back in...

You would not swap in the old one after you have rebuilt it? I guess if your unsure of the process, or don't have a soldering iron, this could pose a problem.

For some, it's better to just purchase a new one.

[bbh03]

Repaired doesn't last forever I guess. Mine crapped out again today after less than one year. Time to go with the new design.