Low water cutoff not working after cleaning pigtail

The switch has a Dead Band between water feed and burner cut off. The Dead Band (between the Red and Orange lines in the image below) provides an opportunity to feed water without shutting off the burner. If the float moved freely but does not drop far enough it may behave that way, can't get past the Dead Band. Or the contacts are bad. With the switch removed from the float linkage it can be better tested.

Well that sucks… A new 67 is expensive. Now you see that is why I only recommended removing the switch and the float. You may be able to clean up the 67's threads with a sharp pick, a thread file and do a final thread cleaning with a Tap or a thread chasing tool. To me messing with things that don't need messing with invites other issues. If you want to mess with other stuff than what is just actually needed to repair the issue do it in the Summer time. If you use a Tap or a thread chasing tool remove the float first so the float is not damaged.

Is half the plug is still in there ??? Or did it rust away. If the other half is still in there does it leak ?. If it is still in there and does not leak, I would make that a summer project and move on with the main issue.

Edit: I originally assumed that was all that was left of it. It can be replaced I think it is a 3/8 inch thread.

" What’s left of the plug won’t thread on " I would not expect it to since it is probably too wide, Pipe threads are tapered.

Not really seeing any threads in your picture.

Fix the plug issue before putting the float back in for good. You can temporally reassemble for testing, less screws. Carefully clean the sylphon or bellows so movement is not restricted by that. Clean that rust on the inside of housing, it may not take much to limit the float movement.

@John Boyer

I don't remember what size that plug is 3/8" pipe thread (I think). But anyhow it is a standard pipe plug available at big box, hardware or plumbing supply store. Get a brass one if you can.

get a drill bit and drill a hole in what's left of the plug. If it was me I would take the whole thing off the boiler and go through everything. Doing it on the boiler is difficult.

You have a union on the bottom connection so there is no reason not to take it off the boiler. Then it will be easier to get the rest of the plug out. Drill it out a big as you can and pick the remaining threads out. You can get a 3/8 pipe tap if needed.

The switch the top two terminals are for the burner as you mentioned. Don't forget if the float is pushed up that pushes the switch lever down and, in that position, the top terminals should be "made"

If I recall correctly I uses a utility knife but the knife blade did not touch the float in any aggressive nature. Its a slow process.

Well if it fell apart that easily, maybe it is better to find out now rather than in January. Hard to tell exactly what is going on in the picture. Although it looks like mud accumulation at the bottom of the hole in the picture.

To me it looks like the threads are either all gone or all filled up metal from the old plug. If there is nothing left of the 3/8 inch threads maybe it can be drilled out and tapped for 1/2 inch threads. With a 3/8 inch pipe plug you will know quickly.

permatex will stop the leak. you can see if you can stick a couple thousandths feeler gauge between the cover and the body with it tightened down. it shouldn't slip in there. i don't know about this, how thick the cover is, but i know sometimes you can warp the corners and make the gasket leak if you crank down too much on small parts like that.

If the gaskets two mating surfaces were thoroughly clean of the remnants of the old gasket, flat surfaces with no defects, and all the screws torqued equally without deforming the round metal plate(s) it should not leak.

A gasket sealer from an automotive parts store could be used.

I would not count on it self sealing over time and depending on where it is leaking switch contamination could be an issue. I'd try to identify the cause of it leaking.

The screws into the casting should not need to be crazy tight just snug. Too tight may deform the thin metal.

The other 4 holes are for the orientation of the round electrical box, the long screws.

The gasket may not be the leak. if the bellows was compromised during the cleaning, the steam or water can leak thru the crack in the bellows and be coming out thru the switch activator lever

fill the bellows/float with water and let it sit a while and see if it leaks out somewhere

cough safgard