The blower on my OLD forced air natural gas house heater will keep
running. Oddly, if I just gently tap the sheet metal housing next to
the blower, it stops running? Is the fan limit switch getting stuck?

wrote:
The blower on my OLD forced air natural gas house heater will keep
running. Oddly, if I just gently tap the sheet metal housing next to
the blower, it stops running? Is the fan limit switch getting stuck?

Sounds like it ... or maybe it's right at the borderline of shutting off.
Try adjusting it a small amount and see if that helps. It might.

Pop`

wrote:
The blower on my OLD forced air natural gas house heater will keep
running. Oddly, if I just gently tap the sheet metal housing next to
the blower, it stops running? Is the fan limit switch getting stuck?

Actually there are typically two switches in that assembly. The limit
switch to turn off the burner if temps go past set-point, the fan
switch
to control fan relative to furnace temp. Some have two adjustments-
obviously you want the one that's got markings in a reasonable range
for discharge temp. If they're still visible.

J