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Brian HVAC Guy
Brian HVAC Guy, HVAC Technician
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Trying to replace my LR1620 to the RTH7600. I have a heat

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Trying to replace my LR1620 to the RTH7600. I have a heat pump and a furnace installed. There is 4 wires coming out of wall (R,W,Y,G) which were hooked up to the corresponding letters on the LR1620. I also have a jumper wire that goes from Y to "1" on the LR1620. The new unit does not have have the option of "1", which I'm guessing is some sort of Aux wire connecting to Y. When I just connect the 4 wires to the corresponding connections on the new unit, power up at panel, I don't get any power to the new unit at all. Need help if you are familiar. I can upload images if needed.

gotoman for ac : Russ here.. Please upload images , I will be herer for one more hour. Russ

New Unit w/ wires
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Old Unit with Jumper still in
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Front of old unit
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There are the images, let me know if you need any more images of anything. This is with the new unit currently hooked up, but I still have power disabled to the A/C and Furnace until I have it hooked up correctly.

Hi, I'm Brian. I'm here to answer your HVAC question to your complete satisfaction!

I see that your question is back on the open list and it appears Russ had to leave. If you could take a picture of the front of your old thermostat with the cover off making sure to show the numbers on it that would be helpful. It would also be helpful if you can give brand and model number(s) of the equipment you are trying to control. I will do my best to find a solution for you.

Customer: replied 3 years ago.

Central Air Conditioner: Goodman CKL130-1L

Furnace Model: Goodman Janitrol GPD050-3 REV B

Image of old thermostat:


Old unit

Thanks for the picture. I may be able to use those numbers to figure out what's going on. I'm sorry it took so long to get back to you but I was just now alerted that you responded. I will try to get back to you within a couple hours or less. Thanks, -Brian
Ok I have looked up your new and old thermostats and your furnace and a/c unit literature. The number you provided for the Goodman condensing unit is a cooling only unit and therefore not a heat pump which explains why you only have 4 wires at the thermostat. The way you have it connected is correct. There is either a problem with the new thermostat or possibly an issue with your system itself. With the thermostat base on the wall and the thermostat not attached you should read 24-27 volts ac from the red wire to all 3 other wires. If you don't then there is a problem with the low voltage transformer or fuse in the furnace. If you do then there may be a problem with your new thermostat. If you have voltage at the thermostat you can short the red wire to G and you should get the furnace blower to run, R to Y should turn on the a/c unit outside and R to W should start up your furnace. If those tests work, the thermostat is indeed at fault. Please message back if you have any further questions.
Brian HVAC Guy, HVAC Technician
Category: HVAC
Satisfied Customers: 854
Experience: I have been an HVAC/R mechanic/technician for 30+ years.
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Customer: replied 3 years ago.

It was the new unit. There was 27ish volts going to all 3 wires. I took it back and exchanged for a new unit. Pretty obvious when the new unit powered up with AA batteries. Thanks for all the help, it helped to know I was on the right track with the wiring before assuming it was the unit.

That's great I'm glad we figured it out together! Honeywell thermostats are high quality thermostats but every once in a while a bad one out of the box does happen. Good luck and thanks!

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