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older Millermatic 130 auto arc

JohnW

Active Member
#21
Great idea on jumpering with a fuse. In all the electronics work I've done, I've never tried that. I will add it to my mental bag of tricks (if I remember).

Light bulbs are also very effective current limiters when you are jumpering stuff. I often use them for safety when playing with 120V stuff. An incandescent light bulb has a low resistance when cool, so it will flow some current without a problem. Once it lights up, the resistance climbs dramatically so it quickly limits the current. According to one Google article, a 40W light bulb will go from about 100 ohms cold to about 1500 ohms when lit up. Obviously, you need to use a light bulb rated for about the same voltage as used in your circuit.
 

Janger

(John)
Administrator
Premium Member
#22
oh my ... my furnace is acting up again.

Thanks everyone for comments last time. Resoldering the cracked connections seems to have solved that problem and it now runs. Next!

This time it's making annoying squealing noise when the fan runs. When I hit it it stops for a while then returns.
I took the motor apart, cleaned and oiled the bushings. 3-1 motor oil. It was much better for a day. now it's back to this. Fan is tight on shaft. bolts are tight holding the furnace fan on the housing.
New motor? replace bushings? something else? anyone know?

Btw this is a Stirling garage guys furnace. Don't buy one. No one has heard of it, there's no parts, and it's hell to take apart, and it's not reliable.
 
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Jwest7788

Well-Known Member
Administrator
Premium Member
#23
Did you find signs of too much "rubbing" when you had it apart?
Squealing = rubbing, in my mind anyways.
 

Janger

(John)
Administrator
Premium Member
#25
Well yes the shaft seemed to be discoloured where it goes through the bushings. I cleaned and oiled the shaft and the bushings. Can I replace the bushings? Try bearings?
 

Dabbler

Well-Known Member
#27
here goes... You probably have oilite* bushings that have either dried out or weren't properly prepared.

To prepare an oilite bushing , you soak it for a while in varsol (think 2 days) and then heat it gently in an oven (NOT your kitchen!!) until it hits about 200- 250Degrees F. then douse it in the correct oil - the last time I had to do this was 30 years ago, but I think it was fully clear synthetic oil somewhere about 5 weight. After cooling, leave it in the oil for a day or so and reassemble. -- Most any lightweight oil will do, and some people skip the varsol step and heat the bushing in the oil bath. Check the web for the current wisdom.

*oilight is a trade name for a sintered bronze bushing that is very porous. They are most common on furnace type motors (Coincidence? maybe.)
 

Janger

(John)
Administrator
Premium Member
#28
IMG_0513.JPG
here goes... You probably have oilite* bushings that have either dried out or weren't properly prepared.
.)
That's pretty interesting Dabbler. I took it apart again and the felt pads for the oilite bushings were quite saturated. I don't think lubrication is the problem. Looking closer the shaft is scored and I think the bushings are too. I can feel it is oval shaped spinning it. Time to buy a motor I suppose.

I hung a ordinary cooling fan in the furnace while like you suggested the other day. Seems to be working temporary while I sort this out.

Thanks for the help guys. Photos...
 

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Dabbler

Well-Known Member
#29
Tt looks like it was dirty: probably from the manufacture... sheesh. Many companies are not doing a good job of QC. You should let the garage guys know it is a dud. Even if you've had it a few years it is better for them to know they have as dissatisfied customer. They might just throw in a motor if you give them a respectful complaint.