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Old 01-23-2008, 10:13 AM   #16
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marsh furnance


It seems to me that mine had a schematic glued inside the housing . You might look around the upper area behind the air filter. Also, my last post was incorrect. The gas valve worked fine but the high res wire kept the blower from coming on. This had also caused the upper limit switch to open until it cooled down. Sorry for rambling. this memory is about 8/9 years old.
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Old 01-23-2008, 10:22 AM   #17
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marsh furnance


Not trying to be cute, but is the gas valve in the on position? Thermostat selector turned on? Assuming a 2 wire t-stat,do you have 24V on both wires? Also, it won't light the burner with the front grill removed because of the safety switch.

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Old 01-23-2008, 01:46 PM   #18
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marsh furnance


I looked for a schematic but none in the top or botttom of unit.Yes the gas valve is in the on position.The thermostat shows 24vac.The bottom panel switch is depressed as I try to lite this thing.Thanks for your ideas and help.
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Old 01-24-2008, 03:07 PM   #19
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If you follow the thermostat "call for heat" wire from where it enters the furnace it should lead you to the limit switch. Probe both sides of this switch for 24v. If you have 24v on both sides continue to follow the wire, checking for 24 at each connector. Or you can start at the gas valve end of the circuit and follow it backwards.
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Old 01-24-2008, 04:29 PM   #20
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Ok thanks for the info and help.
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Old 02-24-2008, 12:21 AM   #21
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I happened to be on location with my Marsh furnace today and remembered to look it over. The schematic is printed on the right blower housing. I have no way to photograph it but it is very simple. One side of the transformer 24v goes to the thermostat and returns as "call for heat", thru the limit switch, and on to the gas valve. The other side of the trans 24v goes thru the "main reset" which is located on the upper bulkhead of the cabinet between the blower wheel housings, on down to the gas valve. I also noted that all of the wiring is of the fine strand variety which is prone to develop resistance. Good luck.
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Old 02-24-2008, 05:21 AM   #22
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Thank you for your time and this good tip.Do you know if and where parts are available for this unit?Thanks again.
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Old 02-24-2008, 09:46 AM   #23
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except for the sheet metal components and an application specific gas valve, it appears to have been assembled from stock parts available at an appliance parts house. My gas valve had an integral 2 speed fan switch and was unavailable so I replaced it w/a standard valve and joined the wires for high speed. Everything except the gas valve and transformer can be temporarily substituted by a pair of jumper wires for testing purposes. You may find parts on ebay. Let us know how you come out.
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