Thermostat wiring diagram, t-stat off wall and wires not marked

Sounds like the fan relay is getting voltage bleedover from the 24 volt wire. Could be the thermostat also but most likely there is a bare spot on the wire going from the fan relay to the terminal marked "G" on your thermostat that is touching the wire that goes to the terminal "R". Easiest way to fix this is to run new T-Stat wire from thermostat to the indoor unit or the blower motor if it is a package unit, making sure that the "R" and "G" wires have good insulation on them and are not touching. If you have an 8-wire T-stat wire you can sub out the wires marked "R" and "G" with different color wires that are not being used, just pay attention to how they hook up and you will not have to pull a new wire through the wall. Good luck!

if you open the door to the furnace or air handler (which ever you have ) and note what color wires go to what on the terminal strip or control board, and make it match what you have at the t-stat. In some cases the wire marked "Y" at the t-stat is mearly twisted to another in side the furnace and not attached to a terminal strip.

Is your wiring where it's hooked into the furnace still identifable as to color. If so one way to tell whats what is to remove wires from furnace one at a time and disconnect all wires from base of thermostat. Use a ohm meter and one very long test wire. Hook to known wire on one end and use test wire to check wires on t-stat end. When you read closed circuit reattach wire to furnace and lable t-stat end as to color. Connections on base of thermostat should be marked with R,W,G,and y. Check each wire one at a time and when you know what color each wire is hook t-stat base back up,put cover back on and check out. A much eaiser way if you can identify wire color and existing wire is accessible in basement or whever your furnace is . Discconect wires from furnace and see if you can pull wire back up to thermostat. If you're lucky they won't be stapeled inside wall. If you can move wire easily buy approximate length of new wire at hardware store. Most of them will sell wire by the foot. Strip about 3/4 inch of insulation from each wire and twist all wires from old to new and wrap all of it with electrical tape. Carefully pull new wire to t-stat and connect there and to furnace. Good luck. I hope this helps. Thanks

I would switch to a two wire heating only stat It sounds to me like they have the boiler wired into cooling side. Do you also have to set switch on your t-stat to cooling or leave it on heating. Just curious. I would still go with two wire stat. Thanks.

what kind of thermostat to you have, did you purchase the thermostat with the unit are you upgrading to a electronic thermostat, If you are using the mechanical thermostat that comes with the unit you will not need a thermostat. please see the link below and page 11
http://www.wfc-fc.com/pdf/Monterey_Top_Vent_IOM.pdf

grainger has them- home depot. wire is easy wire one side straight to 1 wire on in coming power the other side use your thermostat to break curcit ie wire into stat out of stat to voltage

one set goes to your heater,,,,
red/black gr
the other set is either your voltage in, or your t-stat will control 2 units

both thermostatats will have terminal designators R,W,Y,G, possibly O/B, C, W1,W2, Y1, Y2, etc.
Simplest method is to remove wires from old stat one at a time. mark where they came from and then install at same desinated terminal on the new t-stat. Hope this helps. be sure to shut off power supply to the unit (furnace) first. The wire coming to the R (RH,RC) terminal is the 24 volt a/c hot, all others are feeding back to perform given function.

To get your heat going take the red wire hook it up to R on t-stat. Take white wire and hook it to W on t-stat. Take the green wire and hook it to G on t-stat. that will get you heat. Now I need for you to go to the unit where the wires hook to the furnace circuit board. I need to know what color wires go to what on the board. Might have to take off bottom panel. should only be using 4 or 5 wires. Get back with me and will complete the wiring. Be sure no wires at the t-stat are touching each other as this will short out transformer. So tape them off or cut flush so wire and insulation are flush. ken

the normal wiring for stats is white=w=heat,red=r=24volts,green=g=fan,blue=c=common,yellow=y=cooling.
see what ties into your furnace board and match the terminals.