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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 5648
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I installed a honeywell wifi thermostat to replace my older

Customer Question

I installed a honeywell wifi thermostat to replace my older unit. My older thermostat only has 4 wires. So I moved the G wire to C. On the furnace side I moved the G wire to C and put a jumper between G and Y. Problem is I can't get the fan to go on at all...even when the AC kicks on outside.
Submitted: 1 year ago.
Category: HVAC
Expert:  Comfort Specialist replied 1 year ago.
Hello there, can you tell me the model# ***** your thermostat?
Expert:  Comfort Specialist replied 1 year ago.
And did you jump the Y and G at the furnace or thermostat or both?
Customer: replied 1 year ago.
RTH9580WF is the model number. I did the Y and G jumper only at the furnace side.
Expert:  Comfort Specialist replied 1 year ago.
Have you tried it without the jumper?
Customer: replied 1 year ago.
No. I was told I needed the jumper to energize G to run the fan. Since I pulled the wire out of G and put it to C; on the furnace side.
Expert:  Comfort Specialist replied 1 year ago.
With an air handler that is true. If you have a gas furnace most will start the fan without energizing the G terminal as long as Y lands on the furnace Y terminal. Can you check that and give it a shot for me.
Customer: replied 1 year ago.
I'll go try. I'll be right back.
Customer: replied 1 year ago.
I removed the jumper for Y and G on the furnace side. The AC just kicked in, but no fan/no blower.
Expert:  Comfort Specialist replied 1 year ago.
Ok. Now let's move the Y wire at the furnace over to G terminal on the furnace to ensure if we energize the terminal it will run.
Customer: replied 1 year ago.
Ok. I'll try that. Be back.
Customer: replied 1 year ago.
There were two wires on Y, furnace side. One was the same color as on the thermostat side (blue), so I moved that one to the G and left the other wire on the Y still. When the unit kicked back on, the fan did not kick in. FYI, just before I changed the thermostats, the fan was working with the AC on the unit.
Expert:  Comfort Specialist replied 1 year ago.
Very odd. ok take the wires off of Y and G at the furnace. I need you to install a jumper from R over to G at the furnace and press in the door switch. Tell me if the furnace blower starts.
Customer: replied 1 year ago.
I took out the wires from Y and G at the furnace. I put a jumper from R to G at the furnace and pressed in the door switch. No blower.
Expert:  Comfort Specialist replied 1 year ago.
In this case something else is going on.Are you positive the blower was running before with the old thermostat?
Customer: replied 1 year ago.
Yes. I had the fan set to "on" so I could keep the air moving in the house.
Expert:  Comfort Specialist replied 1 year ago.
And when you set the thermostat to heat does the blower start after the furnace fires now?
Customer: replied 1 year ago.
Didn't try that. Do I need to put the wires back on Y and pull the jumper from R and G? Do I add the jumper from Y and G?
Expert:  Comfort Specialist replied 1 year ago.
Take the jumper off but leave the other two Y wires out and away from the terminals so not to bump anything.
Customer: replied 1 year ago.
Furnace came on fine. The blower did not.
Expert:  Comfort Specialist replied 1 year ago.
Yeah we have something bigger going on here. See in heating mode that furnace is going to tell the blower to turn on not the thermostat so it shouldn't be anything to do with the new thermostat or wiring. How about trying the old thermostat one time to be sure?
Expert:  Comfort Specialist replied 1 year ago.
We'll keep chatting don't worry about paying for more time.
Expert:  Comfort Specialist replied 1 year ago.
Any progress?