Final Stage Resistor fix DIY

[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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[Weasel]

Good tip, and it should get most of these FSR's back working. The only issue I see is that it can't fix the original cause if the issue which is the inefficient heat sink spikes which let too much heat build up in the unit. The new FSR units are an updated design with more efficient heat sinks to prevent the solder joints from getting heat damaged.

[HEISING]

I agree added sink surface would help. Some larger semiconductors would really help, but the issue is the solder pads. These pads are to small. In the original soldering of the unit, all three pads are the same size as the center pad in each set of three. They were nice enough to leave some extra trace (denoted by solder dots) for the outer pins.

[ScottJ]

Originally Posted by Weasel

Good tip, and it should get most of these FSR's back working. The only issue I see is that it can't fix the original cause if the issue which is the inefficient heat sink spikes which let too much heat build up in the unit. The new FSR units are an updated design with more efficient heat sinks to prevent the solder joints from getting heat damaged.

Do you (or another member) have a link for the updated FSR unit, with the updated and improved design?

I think I'll order an updated unit, and just swap my proactively...



--Scott

[Clockwork]

Originally Posted by ScottJ

Do you (or another member) have a link for the updated FSR unit, with the updated and improved design?

I think I'll order an updated unit, and just swap my proactively...



--Scott

Save some money and order from Rockauto.com
its called a Blower Motor Control Module/Resistor in their catalogue and there are many prices/brands. I bought the Valeo myself last year (though it was only $60 I believe then).

But the Hella brand sells for just $37. So thats nice and cheap

[ScottJ]

Originally Posted by trader4

You should be able to find the part number on RealOem. They've
been making the improved version for many years now, it's not
recent. But they are problematic too. If I had any one that was
working, I sure wouldn't be shelling out $$ to replace it.

One tip with these. They rely on being housed right next to the
blower where the blower air passes over the heat sink fins.
When I replaced mine, I tried to test it, to make sure it works,
with it just hanging down, instead of mounted. I didn't realize
that where it goes, the heat sink fins wind up in the air stream.
If you test it hanging, it will work fine at high speed. If you
slow it to low speed, it gets too hot without the air and will
start to malfunction. So, it's OK to test it for 30 secs or so
like that, but don't run it much longer. Also, if you ever start
to have any issues with yours, remember that it gets hotter
when it runs at less than full speed, so if it's acting up, you
may get it to run better at full speed.

Noted, and thanks for the info and advice! I believe I'll shelf the info, and pursue a repair if mine faults in the future. I'm sure the newer replacement units are all the updated (improved) heat-sink design anyway.



--Scott

[rayxi]

Excellent tip. I have an old FSR in my garage I swapped out that I can try this on. Did you reseal it after the repair?

[HEISING]

I did not re-seal my FSR. I figure, if anymore problems develop down the road, I won't have to remove the potting compound a second time. I think this is the last time I will have to touch it though. It works like a brand new unit. (has been for some time.)

[MINIz guy]

Cool DIY. Our FSR has been pulsing for a while but it hasn't gone crazy and have the blower motor come on all the time. Also a great chance to brush up on my solder skills!

[bbh03]

This has to be one of the best tips I've seen here. Thanks Heising! My fan quit today so I pulled that bastard out, re-flowed the solder joints and its working again.