turn unit off. get repaired.
maybe high limit sensor not working? if it is electrical it may be
connected to the heat exchanger in the upper area. if it is a millivolt
heater it may be a long copper capillary bulb that connects to the gas
valve.
blower may be optional?
also check your carbon monoxide alarm it will sometimes tell you when
the heat exchanger is cracked.

Laura R wrote:
Hi there,

My apartment complex was built in the late 50's, and has for the most
part the original appliances in each unit. (They're actually quite
charming. Push-button electric ranges!) My question concerns the
natural gas heater that I've got.

The model is a "Custom-Aire vented recessed wall heater" that is
installed in the wall between a room and a hallway. It uses natural
gas, and the pilot and ignition work fine. The problem as I see it
seems to be that it may have had a fan or blower attached at some
point, and if so it isn't working any more. Signs pointing to this are
the fact that the wall above the heater on one side seems to creak when
the heater goes on, and there's a crack in the plaster where the wall
gets *very* warm. I think if there was a blower or something, the air
would be circulating fast enough to prevent this, though I could be
wrong.

At this point, anything within the upper metal grills/housing is a
mystery. I got the bottom grill panel off and looked inside the bottom
half of the heater, but I don't have a clue as to what some of the
stuff does. There's an obvious gas pipe with a valve, the pilot pipe
with a separate valve, two large cones that I'm guessing are for
adjusting the air/gas mixture, wires leading to the thermostat (which
seems to be only half-functioning, but that's another story entirely)
and a black sort of brick with wires going to it. Does anyone have any
ideas on what's normal to see in a heater of this age? Diagrams would
be especially helpful.

Thanks!
-Laura