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Fixing a dryer timer

Now for something completely different… a Mechanical Hack. Have an old RCA gas dryer. Started acting up over a year ago, the timed cycle would sometimes not dry or not dry completely. Then recently the permanent press cycle started doing the same. Got so bad nearly every load had to be dried 2 or 3 times.

Thought initially it was the over temp thermostat since that’s common to both the timed and the perm press cycle, but no; turned out to be the mechanical timer.


Dryer-1
Here you can see the innards of the mechanical timer. easy to open up, two screws hold the electric motor on the unit. take those out the motor and back-plate come right off. Plastic ring goes round and round, the little finger rides up and down, pushing the contacts together in sequence. All Open, A+B, then A+B+C, or so that’s what it should do.



Dryer-2
Here in the close-up you can begin the see the problem. There’s lots of arcing on the contacts. In this shot even though A/B/C should be closed, there’s a paper thin gap between B+C, which is the gas turn-on of course! Hard to see here, but the finger that rides the plastic ring, has (after 25+ years) worn a groove in it.


Dryer-3
Out of focus a bit, but you can clearly see the groove that 25 years have worn into the plastic. That means the finger doesn’t push the contacts quite far enough, leaving that gap between B+C.



Dryer-4
So the fix. You could try to fix the finger that rides the plastic ring, but that’s a high friction point so likely to tear out any bit of glue / plastic you put in there. Also changing the shape of the finger too much will change the timing too. So the better approach is just to increase the amount that the arm pushes the contacts together. This is a low friction place, it really just pushes in and out, so the glued in plastic to change the finger shape likely will stay in place.

A little super glue and a bit of plastic….



Dryer-5
Trimmed the plastic down to match the outline of the lever arm.

What I neglected to show is sanding down the added plastic to get the proper thickness. It’s a bit of “best judgement”. If you leave too much; it pushed the A+B contacts together even in the “OFF” position. If you take too much off, then B+C don’t get pushed together solidly. So it’s a bit of trial and error. Sand a bit, fit the arm back in the switch (without the motor) and give it a spin by hand to check the action.

Once you’re satisfied with the resulting action, slap it back together and put it back in the dryer. Should be good for another 10 years now!