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Rick Mather
Rick Mather, HVAC Technician
Category: HVAC
Satisfied Customers: 3634
Experience:  35 years experience, HVAC
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I need a wiring diagram for a robertshaw thermostat. I am

Customer Question

I need a wiring diagram for a robertshaw thermostat. I am reinstalling it and I can't get the auto fan to work. It will only work in the fan on position only... what did I do wrong??
Submitted: 7 years ago.
Category: HVAC
Expert:  Rick Mather replied 7 years ago.
Sounds like the fan is wired correct if it works with the (on off auto) switch.

R = Red 24vac
G = Green Fan
W = White Heating
Y = yellow cooling

R could be jumped to Rc if only one transformer this may be your problem other wise it will have seperate 24vac to it
Customer: replied 7 years ago.

Ok these are the color of wires I have. When I remove this thermostat to replace it with a programable one I coded the wires to beable to get them correct when ever I moved.


Color of wire = code on Thermostat


Green wire = RH

Goldish Brown wire = G

Yellow wire = Y1

White wire = YRH

Cream color wire = W


seems like the fan only is running in the "Fan On" always... What do I do???

Expert:  Rick Mather replied 7 years ago.
The only wire that makes sense is the Yellow to The Y

White + YRH does not make sense either Please check your old wiring and what you have at presently

Normal wiring are as follows

R + red which supplys 24 vac and Rc could be jumper to R
W is other side of heating when R to W closes heat starts
G which when R to G closes turn fan on
Y which turns cooling when Rc closes to Y

Customer: replied 7 years ago.

There is a red wire but it was never used when I took this dang thing off in the first place.


here are the positions connections that are written on the thermostat itself








there is SB-4A-5AJ written on the left side of the thermostat... if that helps

Expert:  Rick Mather replied 7 years ago.
What are the AZ B mean, and W G, and A RC, Y RH

Are this all seperate terminals?
Customer: replied 7 years ago.

yes those are all the terminals Starting with B in the 12 oclock position and going clockwise they read B, O, G, RC, RH, Y, A, W, and AZ when I removed this thermostat I marked each wire with the letter from where I took it off the terminal.


but now I am wondering if 1 or more wires need to be connected on the same terminal.



Expert:  Rick Mather replied 7 years ago.
The one that came off the Rh has to go to Rh and Rc. Who ever wired this Thermostat was on drugs or something maybe colored blind
Customer: replied 7 years ago.
Great!!!! Guess I just need to check my neighbors connections and hook it up the same as it. thanks for trying to help... but you didn't give me the answers I needed
Expert:  Rick Mather replied 7 years ago.
Well hope they are the same and good luck

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