Hubby bought a used Pfaff Hobbymatic 939 for $50, listed as a running machine, with a presser foot lift, which put NO PRESSURE on the presser foot, & also, got stuck in reverse.
To clean the presser foot lift spring & allow it to put pressure on the presser foot again, you usually have to lower the presser foot lever, so you can open the face plate, to access the presser foot top & spring, you remove the screw, or part on top of the presser foot lifter, pull out the spring, it will be stiff with thick, dried up lubricant, almost like honey & wax from a beehive, that dried out. I used alcohol on Qtips to clean the tube out, then more to clean the spring. Once it is all clean, reassemble in the reverse order, & move on to the reverse lever, stitch length issue...
The cause is once again, old lubricant, or oil which migrated out of the metal or plastic, & dried to a sticky resinous glue, so the parts can't move against each other anymore. Reverse & stitch length use the same mechanism, so when stuck in reverse, the spring can slowly pull itself back, but if too weak, it won't be able to allow full stitch length. I already dealt with the old dried up lubricant up above, in the needle bar area, affecting the presser foot lifter & spring that controls presser foot pressure, & got the machine sewing & running extremely well, but the first time I used reverse, it wouldn't go back to straight stitch forward, but it ran great in reverse, at all speeds.
Underneath many of the 1980s to 2000 Pfaff Sewing Machines, there is a metal pivoting rod, around which, the plastic & pvc parts which control stitch length & reverse, are supposed to pivot. Over time, particularly if exposed to much heat & humidity, a tiny bit of oil either works its way out of the materials themselves, or migrates to the area, & dries to a sticky resin, gluing them firmly to the pivot rod. To check if this is the problem, all you have to do, is remove the bottom of the machine, & under the motor, in the "pillar" of the machine, you will see the tiny black set screw, which holds the rod in place. If you loosen the set screw at all, the rod suddenly begins to pivot, allowing the lever which controls reverse, & stitch length, to pivot the rod, so it seems to fix the problem.
It is not fixed, but you have located the exact spot which needs cleaned! If you just loosen the set screw, over time, the rod will work out of the machine frame, & could damage the machine, so you can t just loosen the set screw. You have to disengage the lower piece of the reverse spring, from the bottom of the plastic piece it is hooked to, then remove the C clips on the rod, & the set screw far enough, that you can remove the plastic pieces from the rod completely. The rod can stay in the machine frame, you can use a Qtip with alcohol, to clean the resin off the rod, push it back & forth through the frame if necessary, to get to all of it.
Use another Qtip in alcohol to clean inside the tube area of the 2 pivoting plastic parts, & when they are clean, replace them on the rod, & make sure they pivot freely, before putting everything back together. If they pivot completely freely, go ahead & replace everything back in the machine, making sure you get the gears back in the correct positions, & the "finger" that sets into the helical groove in the plastic wheel, which controls the stitch length & the reverse lever. Once you are sure everything is properly aligned, replace the C clips on the pivot bar, tighten the set screw, then reattach the lower section of the spring, on the plastic piece that controls stitch length. Sorry, I don t know better technical terms, but that s the basic reason these great machines get stuck in reverse! Do NOT lubricate this area! That will cause the same exact problem, when it dries up! Happy Sewing!
Becky
Becky
January 2016
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