Where to find high limit and fan limit controls on ancient Rheem gas furnace?

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Motorapido

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Where do I find the high limit switch and fan control switch on a 1973 vintage Rheem 3040 -110 gas hot air furnace, standing pilot, natural gas.

I'm guessing the fan control temperature switch is inside the jacket-surface-mounted galvanized box with the white push button for manually turning on the fan.

Before I start removing panels from the outside to get a look inside, I'm seeking more info. Would both the high temperature limit switch and the fan switch be inside of or behind the manual fan box with the fan push button, which is mounted on the furnace jacket, up high and near the top of the furnace?

My huge local plumbing/HVAC supply desk professionals can't seem to find schematics or parts data on this 1973 Rheem furnace, which seems strange for such a large brand name. I'm assuming that after I locate and remove the high limit switch and the fan sensor switch that I will find numbers imprinted on those two parts so that my HVAC parts counter can sell me replacement control switches.

Please advise on the location of those two control switches, and many thanks.
 

John Gayewski

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Why do you think there is a fan sensor? There might not even be a limit switch. Some of those old furnaces lack a number of sensors and controls that modern units have.

A unit that old would not have info held by the manufacturer. A lot of manufacturers don't even carry info on units more than 10 years old.

If you pull off the front panel the control area usually inide of the cabinet. Can you take a picture of the unit?
 

Reach4

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My huge local plumbing/HVAC supply desk professionals can't seem to find schematics or parts data on this 1973 Rheem furnace, which seems strange for such a large brand name.
Did you remove the cover on the blower area and see if the there was a schematic inside the cover?
 

Fitter30

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Fan and limit control 2.5" x 3.125" round dial three little levers. Do not turn dial wires come out with a pocket screwdriver push into the slot and pull wire out. Need to pull control out and measure from back of control to the length of the sensor. Doesn't matter if it's honeywell or white rogers. Tube length has to be about the same. Ebay amazon or suppw to set it uplyhouse.com. white pull knob for fan.isn't needed unless u want to just run the fan. Decide to buy a new control i can u how to set it up.
 
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