Set screw won't come loose on draft inducer for Carrier furnace

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tracyballard

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I've got to replace the draft inducer motor on my Carrier furnace, but I need to get the blower wheel off and the set screw will not budge. I've got the right allen wrench, even wrapped some tinfoil around it, but the screw will not turn. I've also been soaking it in gun oil and WD-40. I'm using a lot of force, and I haven't rounded it off yet, but this thing will not move whatsoever. If I can't get this off without messing up the blower wheel I'll have to wait til Monday for heat. Any ideas?
 

tracyballard

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I've been using WD-40 every 10 minutes to soak it good, I've been at this for a few hours now. I use a 1/4 box end wrench on the end of the allen wrench for more torque, and the allen wrench is just about bending, but this set screw will not come loose. I guess I may have to cut the shaft on the old motor with a hacksaw to get the housing loose, and wait for my new blower wheel to get here on Monday.
 

Smooky

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I have a heavy duty 1/2" drive hex bit set that I use when regular hex wrenches just aren’t heavy duty enough.
http://www.tooltopia.com/sk-hand-tool-19733.aspx
You could try heating the Allen screw or the housing up with a torch
Another option would be to use a screw extractor if you can get to it easily to drill a pilot hole in the screw.
 
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You're wasting time and making a mess with WD-40, you should only be using PB Blaster, and that only works if some of it can seep into the threads. If you have time to wait, try a generous amount, and tap the bolt on the head safely without deforming it.

If that doesn't work, you'll need to torch it out with hot heat, like Map Pro in the yellow tank. Don't use generic propane blue tanks, that will heat up the bolt too slow, as the rest of the assembly will act as a heat sink.

You want to heat up just the bolt, as quick as possible, hammer it a few times, and then it will come off with a solid hex socket end on a socket wrench.

Adapting that 3/8 socket to a 1/2 wrench will give you more torque. I'm not sure what you are doing with the tin foil, but have both imperial and metric sets and use the one that is most snug. Don't use 'allen keys', they are really made just for Ikea furniture.
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Reach4

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I've got the right allen wrench, even wrapped some tinfoil around it
You had to shim the Allen wrench with aluminum foil to fit tightly in the hole?

Is the setscrew recessed, or does the setscrew have a head that sticks out of the hole?
 
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You have to be careful about gripping ends with something like a Visegrip, the bolt or screw will be really soft and can twist off and break.

If you aren't able to heat it up as I mentioned last post (squirrel cages are often plastic), then drill out the set screw. When you are putting it back together, re-tap it to use a larger diameter one.
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tracyballard

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You had to shim the Allen wrench with aluminum foil to fit tightly in the hole?

Is the setscrew recessed, or does the setscrew have a head that sticks out of the hole?

It is recessed. I've tried a 7/64 and a 3mm allen wrench - the 3mm is closest to the size but is still not perfectly the right size - although really it hasn't slipped yet, the allen wrench is bending before it gets that far. The only other thing I can get in there is a T15 torx bit and use a 1/4 inch open end wrench to turn it, there's not enough room in this small birdcage for anything else.

I've just about decided I'm going to have to remove about 3 fan blades on the side of the set screw to get some more heavy duty tools in there, or just to drill it out, I guess I would also have to remove 3 on the other side to keep it balanced. I could try some PB blaster, but I don't have a welder to heat it up, although I have a heat gun that puts out 1000 degree air. I may try that first. thanks for all the replies!
 
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A Map Pro gas torch isn't a welder at all -- it's made just for heating up quick. The kits aren't expensive. You might want to ask local friends that are automotive inclined to help here. We are used to torching off frozen and rusted bolts and nuts.

A heat gun is just going to slowly heat everything up and defies the whole point of precision heating. You don't want to deform other parts of the unit that we don't want to unnecessarily heat.

Altering or deforming the fan is dangerous and will eventually cause indirect permanent damage to your entire unit. If you destroy the fan taking it off, replace it with a new one, no questions asked.

All of the things you mentioned are solutions that won't work, and no hired professional would ever try any of them. It may be a good idea for you to call a service professional to get this done correctly. Best of luck.
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tracyballard

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Well, I was able to finally get the set screw loose with a screw extractor set. I had to take 2 blades off each side of the fan to get it to fit in there, but I was able to pop the screw loose pretty easily once I got access with the screw extractor and an electric drill. I was even able to reuse the sqirrel cage (even though there are 4 blades missing), and even the set screw. The fan seems to be balanced fine, and everything works great now. I guess I should put the new blower wheel on when I get it tomorrow, but it's tempting to leave it alone. thanks for all the tips!
 
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