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If your Atwood water heater has the optional 110 Volt electric heating element, it would be located on the rear of the tank. You should have a door or panel to gain access to operate the ON/OFF switch. See lower/center diagram.
Diagram
Number Description Part Number
Not Shown 130' Front thermostat (not shown) 85-91470
Not Shown Adjustable Thermostat (retrofits Front-mounted theromostats) (NOT SHOWN) 85-93105
Not Shown Gas Line Grommett (not shown) 85-92610
1 Flue Box and Gasket 85-90960
2 Grille, New Style in Door 85-92640
2 Extended Grille 85-90002
3 Access Door ( 6 Gal.) Colonial Wihte 85-91514
4A Potted Circuit Board (Spade Electrode Connection) 85-93865
5A Electrode (Local Sense) 85-93868
6 Wiring Harness 85-93189
7 45 Degree Elbow 3/8" 85-91044
8 White Rodger Valve (6 & 10 Gal.) 85-93870
8A Gas Valve Bracket 85-93243
9 Orifice Holder 85-91563
10 Main Burner Orifice 6 Gallon 85-92742
11 Main Burner 6 Gallon 85-91638
12 Door Hardware Kit 85-91858
13 Set of 4 Corner Brackets 85-91928
14 Ring & Gasket Kit for Service Tank 85-96010
15 Styrofoam tank cover - bottom 85-92220
Not Shown Styrofoam tank cover - top 85-92221
15A Drawn Pan (Electronic 6 Gallon) 85-91802
24 110VAC Elmnt/Gskt (screw in) Kit 85-92249
28 Font Mount E.C.O./thermostat 85-91447
29A Drain Plug Kit 1/2" 85-91857
30 Pressure Temperature Relief Valve 1/2" 85-91604
30 Pressure Temperature Relief Valve 3/4" 85-90028
31 Switch 12 VDC-White 85-91859
31 Switch 12 VDC-Black 85-91959
33 Thermal Cut-Off 85-93866
Not Shown Fuse, Mini 2AMP 85-90145