FSU swap - really different looking new part!

[98OrientBlue]

My blower was exhibiting intermittent problems, and after checking the common causes, I decided to swap my FSU. When I pulled the old one, I was surprised to see it it looked totally different from the new unit. It was much beefier and had a metal case. I guess that's why it lasted almost 20 years before crapping out!

Is the new design less reliable? I bought it from FCP Euro, supposedly made by Rein, but the actual part says Sitronic.

Thoughts?

[edjack]

That's the current design. It has 39 fins on the heat sink.

Amazing that the old one lasted that long. I went through two of the old design in 15 years.

Stuff it in!

[98OrientBlue]

I followed these excellent instructions:

http://www.540i6.com/finalstagereplacement.html

I tried different body positions to release the FSU. Working on my back didn't work. I finally sat in the seat and reached in with my right hand, pressing on the tab with my thumb while pulling on the connector with my fingers. That did the trick!

[edjack]

I've always had to kneel on the floor beside the car to get the damn thing out!

[geargrinder]

Yeah the contortion is something you learn. I can pull an FSU in about 3 minutes now but only knowing exactly what it all feels like blind up in the hole from experience. Sometimes/often the connector is sticky and does't want to pop off...

There was an aftermarket FSU sold for a while that was more 'solid state' (ie instead of big resistors and heat sink it was some kind of semi-conductor - MOSFET probably) but that seems to have gone away although I haven't tried to look for it in a while. Seems like that should have always been what BMW used.

[djb2]

The modern ones likely did high frequency PWM using MOSFETs. If done correctly, that produces much less heat but it does result in a bunch of electrical noise (radio interference), and the design has to done carefully to avoid voltage spikes from motor commutation killing the MOSFETs

[98OrientBlue]

Wow, some real EE's here :-)

Yeah, the whole analog power resistor thing seems so outdated. A modern brushless motor and controller would do away with all that heat generating cruft.

[HoZy]

I had a new style Meyle FSU melt in a week, I got my money back & did the forum noted repair on my original FSU with the jumper wire & resoldering it & it's been working for 6months again, 20years on the factory FSU Vs. 1week on a new one.

Cheers
Mat

[98OrientBlue]

I had a new style Meyle FSU melt in a week, I got my money back & did the forum noted repair on my original FSU with the jumper wire & resoldering it & it's been working for 6months again, 20years on the factory FSU Vs. 1week on a new one.
Cheers
Mat

Mat,
Cool that I didn't throw out my old one! Can you direct me to the site with the repair instructions?
Thanks! Jim

[HoZy]

Pic I managed to find on my phone of my repair,

Just have a google of E39 FSU SOLDER REPAIR or something along those lines.

FSU01.jpg

Cheers
Mat

[98OrientBlue]

Pic I managed to find on my phone of my repair,

Just have a google of E39 FSU SOLDER REPAIR or something along those lines.

FSU01.jpg

Cheers
Mat

Interesting.... I can see that quite a lot has been written on these little things! I didn't read all of the posts, but I found one by "cn90" that showed his fix looking like this:

Attachment 632371
As you can see, it doesn't have the extra wire that yours has. What's the blue wire for?

[TerraPhantm]

Interesting.... I can see that quite a lot has been written on these little things! I didn't read all of the posts, but I found one by "cn90" that showed his fix looking like this:

Attachment 632371
As you can see, it doesn't have the extra wire that yours has. What's the blue wire for?

Presumably that's a soldered wire to bypass the part of the circuit that failed.

Considering that it's not unheard of for the older FSUs to cause fires, I'd recommend just replacing it.

[98OrientBlue]

NEW-FSU.jpg
Aaarrrggh.... back again! The new FSU went out already! I contacted FCP Euro, which offers a lifetime warranty and they assured me that my bad FSU is probably just a fluke, and that I should feel confident about ordering another Rein unit.

Now, for some reason, I just can't pull the bad FSU out. I obviously did this once before, so I thought it wouldn't be too hard to do again. But, try as I might, I can't seem to push the retaining clip down and simultaneously yank the FSU out.

I noticed that the new FSU has an extra hook on the back side of the base (see picture; highlighted in green). The original FSU has no such hook. Could that be causing the unit to get hung up? Any suggestions?

Thanks!

[geargrinder]

1. Rein tends to suck. I avoid.
2. Yep. They can be sticky as I said way up above.
3. Keep wiggling squeezing and janking on it.

[98OrientBlue]

3. Keep wiggling squeezing and janking on it.

GG, is #3 in reference to the hook I was asking about? In other words, there is no real elegant way to release that hook other than "janking"? ;-)

[98OrientBlue]

+1 to "janking".... finally got the bugger out

[geargrinder]

Yep.

I did look up the Rein part and looks like its an OE "Sitronic" part so maybe its OK in this case... (Rein sources a lotta cheap parts that aren't OE but this one maybe is OK?)

But also look at my post about dielectric grease. Suggest you try some on the pins of the connector and re-try the one you have. This part is super sensitive to poor connections on its pins - I expect due to a combination of sensitivity to resistance + extreme heat cycling causing 'movement' on the connectors.

[TerraPhantm]

1. Rein tends to suck. I avoid. .

Rein = CRP - should be fine

[98OrientBlue]

Yep.

I did look up the Rein part and looks like its an OE "Sitronic" part so maybe its OK in this case... (Rein sources a lotta cheap parts that aren't OE but this one maybe is OK?)

But also look at my post about dielectric grease. Suggest you try some on the pins of the connector and re-try the one you have. This part is super sensitive to poor connections on its pins - I expect due to a combination of sensitivity to resistance + extreme heat cycling causing 'movement' on the connectors.

Yes, the actual part does say "sitronic". I will get some dielectric grease. Thanks!

[bigMphan]

Oh, China. Can you not copy a German design that lasts 15 years to one that will last at least 5???

[98OrientBlue]

IMG_1682.JPGWell, 1 year later, the Rein FSU went bad. Since I bought it from FCPEuro, I guess I'll just keep replacing it. However, this time, I decided to pay up for the actual BMW part.

Much to my surprise, the official BMW part looks EXACTLY THE SAME as the "Rein" part, and in fact has the same exact label! The attached photo is from the Rein part that I pulled from my car and you can barely make it out that it actually says BMW under the black ink! The new part is the same as this one, but is just lacking the black ink.

What gives? Crazy. I paid 3x the price for the same part without the black ink. Sheesh. I'll see what FCP Euro has to say on Monday.

- - - Updated - - -

Oh, China. Can you not copy a German design that lasts 15 years to one that will last at least 5???

The label says "MADE IN GERMANY"

[nyc951]

@98OrientBlue: did the BMW FSU work ok for you? Is it still functioning properly? I need to order a new FSU and deciding which "brand" to buy. Thanks.