Thermostat has broke - need help with the wiringl


So I was taking a look at my current thermostat and furnace motherboard wiring setup and I noticed that it was inconsistent coloring scheme between what is hooked up at the furnace motherboard and what is coming out of the wall by the thermostat.

Below is the link to the images of the furnace motherboard and thermostat setup.

What I find is the following for the wiring colors

Thermostat ---> Furnace

W = White ---> White, R = Red ---> Red, Y = Yellow ---> Yellow, G = Brown --> Green, C = --> Blue

However in the Thermostat image, I see a dark blue wire on the right side that actually wraps around the sheathing of the wire bundle to generate more slack but I am curious if that dark blue wire is the C wire that is just not connected to the thermostat. I know I will have to strip off some of that sheath to expose the dark blue wire.

I would like buzz it out with a multimeter to see if it generates 24V but does anyone know the proper way to test...

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Im wiring the control circuits for a Fire Pump ,, methods for a raceway include LFMC.. is there a Lendth restriction on this LFMC … read more

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Electrical code question. Outdoor wiring. There is some wiring run underneath some eaves and underneath of the second story deck that is currently just plain Romax wire.code requires that it be UF out… read more

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i have baldor 5 hp single phase motor 4 wire need to wire it to a drum switch for forward and reverse … read more

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I am replacing a ceiling light and the wiring is knob and tube. I used a non-contact voltage tester and got no signal before I disconnected the wires and now that the wires are...

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First tip: Throw that POS you bought away (or take it bake if possible). Spend a little bit more for a proven, reliable tstat such as honeywell. I have installed and replaced undreds of tstats and I have found that buying a cheap one never pays off in the end.

If you still insist on this tstat...
On the old stat, your red wire is your 24 volts supply voltage. This wire goes to R on the new tstat. As it was on the old tstat, you need a jumper between R and RC.

OB is your shuttle valve on the outdoor unit (heat pump). Usually, this is supposed to be an orange wire, but it looks like they used blue for whatever reason. Hook up blue here.

AUX on the old tstat was for your auxiliary (back up) heat for your heat pump. It appears that with this new tstat, they call it H1. PLace the white wire here.

E was for the emergency heat, which is when you force the back up heaters on at the tstat. The new tstat seems to call this H2. As it was on the old tstat, place a...

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Many times, a malfunctioning or broken thermostat masquerades itself as a faulty furnace. Before assuming that you have an expensive HVAC problem to deal with, first take a look at your thermostat.

In our last blog post, we talked about 5 Furnace Troubleshooting Tips that can help you solve some of the most common heating problems. On the list, we talked about having your thermostat cleaned, set to “heat,” and changing its batteries, but we didn’t go very much into detail.

Sometimes, your thermostat needs a little more attention. What you think is a broken thermostat may just be a neglected one.But sometimes, you may just have to break down and buy a new thermostat because of aging, faulty wiring, an old transformer, or other issues. In this case, we highly recommend investing in and learning to use a programmable thermostat.

You may also be interested in the new, high-tech “smart” thermostats, which claim to learn your habits and automatically adjust...

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humidistat. If using this profile, the blower will run at

75% airflow for the first 10 minutes of each cooling

cycle.The basic cooling/heat-pump

speed should be

selected at or near the top of the range for that nominal

capacity. See Table 3.

Demand Defrost Control

The demand defrost board controls the defrost cycle

in response

to ambient




temperature and accumulated compressor run time. The

heat pump is allowed to operate in the heating mode

until the combination

of outdoor ambient and outdoor

coil temperatures

indicate that defrosting is necessary,

based on the programmed defrost curve. There are four

preprogrammed defrost curves on the board.

A jumper pin is used to switch between the different

curves. The default setting is program two and is the

recommended setting for most standard...

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Is your heating or cooling system not working properly?

This problem could be caused by a variety of issues—like a problem with your thermostat.

Here are some things you can try first to determine if the thermostat is the problem or if the problem lies elsewhere.

How to troubleshoot your home’s thermostat

Turn the thermostat up or down 5 degrees from normal setting

During heating season: set the temperature 5 degrees higher than normal During cooling season: set the temperature 5 degrees lower than normal

You should hear a click when you do this. Wait a few minutes to see if your supply vents blow out air or if your return vents suck in air.

Make sure the thermostat is on the right setting

Just to make sure we’re not overlooking anything obvious, make sure that your thermostat is set on “heat” if it’s winter or “cool” if it’s summer.

If your issue is that your A/C or furnace is blowing air constantly, your thermostat’s...

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Pretty straightforward. It is right up top.

FSM says you have to move the alternator, but I'm not sure that's true. Maybe someone else here will chime in on that, it's been a while since I poked at a 5.9L (hm, about 10 years in fact.. I've been around here too long..)

They like to leak. Make sure you clean up the mating surfaces really well, and of course use a new gasket. Thermostat goes into the groove, then the gasket goes on top of it, then the neck (which may have a "front" stamped on it, if so make sure that is toward the front of the engine).

I'd probably at least slap in a new upper radiator hose while I was in there, you're gonna be mucking with it anyway.. on an '00, all the radiator and heater hoses should have been replaced at least once...

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What you will learn from Troubleshooting Broken Thermostats article:One of the most common trouble calls for HVAC Basic checks of the thermostat to see if it is broken or? The basics of the thermostat Learn what a heating anticipator is and what type of thermostat uses them. Lots of related useful links to help you learn your HVAC system

Troubleshooting Broken Thermostats - The main connection between the air conditioning and heating system and the end user is the thermostat. Beyond the air conditioning and heating thermostat, many people know nothing about the HVAC systems that keep them comfortable year round.

There comes a time when the thermostat has a problem or the end user wants to replace the thermostat because they think it is a broken thermostat. It is not uncommon for a person to call an HVAC contractor and tell the secretary that they think the thermostat is broken because their air conditioner or heating system does not work.

Troubleshooting Broken...
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When you are concerned about the routine maintenance of your car, it is natural to get to a point where you will ask yourself, what is a thermostat? And more importantly, what does it being stuck closed, or even stuck open for that matter, mean to me and my car?

A thermostat regulates the flow of coolant flowing to the engine. When you start your car after it has been sitting, such as in the morning, the thermostat is closed and remains that way until the coolant builds to a specified temperature.

Your thermostat is designed to then open up when the coolant reaches this specific temperature, allowing coolant to flow into the radiator. This operation prevents the engine from overheating.

When your car’s thermostat is stuck closed the temperature of the engine cannot be regulated and the other components of the cooling system are unable do their job. The opposite is also a problem, because if the thermostat is stuck open, the car will never reach the proper...

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In this article, I am going to explain the function and wiring of the most common home climate control thermostats. This information is designed to help you understand the function of the thermostat to assist you when installing a new one, or replacing or up-grading an old one. We will focus mainly on the basics of home heating / cooling thermostats, and first of all, I will explain the function of them.

The thermostat is the control device that provides a simple user interface with the internal workings of your homes climate control system. By the use of an adjustable set-point, the job of the thermostat is to turn on either the heating or cooling system to maintain the desired room temperature in the home, and to turn off the system when the desired temperature is achieved.

The most basic of systems (such as an older ‘heat only’ forced air / gas furnace with a standing pilot light) only need two wires for control. They connect to a two-wire thermostat (generally a...

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I have 1981 house in Washington state with in-wall electric heaters and mechanical single pole thermostats. I want to replace thermostats with something less crappy. I unscrewed one of the thermostats and wiring I saw confused me: there were 3 cables (3 wires each: black, white and bare copper) wired like this (BL, WT and BC are black, white and bare copper wires respectively, grouped by cable, SW1 is a thermostat):

I was expecting to see two cables there: one from electric box and another to the heating unit. Why 3? The only guess I currently have is that the room had two heating units installed initially and then one was removed. No idea why wires are still connected though. Or am I missing...

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My question is really several... Three nights ago fan seem to make a noise like a hovering helicopter. I turned off the system and went to bed next morning cold as hell in the house, nothing working. I had the system on auto heat and set for 70, house was 64. We did smell something like what seems to be coils of the emergency heat. I checked out the contacts outside and unit worked when I depressed the middle section. Returned inside and jumped the r,y,g and unit worked. I replaced the themostat unit in cold came on and worked, however the hovering helicopter sound returned. I turned off unit and now nothing works, not even fan. Need any help I can get. Also, I have one wire with Orange, Black, Yellow, Green, Brown, White, Red, and blue. The Black and Orange are not hooked up and weren't with the last thermostat. Is this correct and where can I get readable diagrams?...

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So I had a new oil furnace installed this week, to replace an existing forced hot air system. Previously I had had a gen 3 (and before that a gen 2) Nest operating the old system. These are really nice thermostats that not only help save money through things like an "auto away" mode, they also work with the Nest smoke alarms to do cool stuff like shut down the heating if CO or smoke are detected.

Anyhow, we ran into a problem that not only had the heating engineer stumped for a while it also resulted in us (the heating engineer and I) jointly toasting a gen 3 Nest. Good job I still had the Gen 2 as a backup!

The issue is that Nest thermostats (as do all similar alternatives) leach power from the HVAC control lines in order to charge their batteries. This works with (according to nest) 95% of systems. The other 5% need to have a common wire run from the furnace. My new furnace was one of those. We discovered this post install when the oil burner was pulsing when idle...

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Please don't get combi and condensing mixed up.

The Combi boiler does away with the hot water tank and gives you instant hot water. The hot water bit is internal to boiler so you don't have to worry about external wiring to give hot water, although the boiler may have the option to run as a combi it is not always used, as when used you can't add hot water from other sources like solar or back boiler, so it does need plumbing as a combi not just be combi type.

The Condensing boiler extracts more energy from the fuel, you can get both combi and condensing in the one boiler and you can get condensing with solid, liquid and gas fired boilers although rare with solid fuel, the main difference to use is it monitors return water temperature and adjusts flame height (not solid fuel) so you need to have TRV's fitted for it to work correct. It does not in theory need a room thermostat.

Out of interest although will not effect you, the solid fuel condensing has a water (or...

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Why Isn't My Thermostat Working?

When your furnace isn’t working properly (or at all), the problem isn’t always the furnace. It could be the thermostat. If the problem is with the thermostat, you’re lucky - that’s usually a much cheaper fix than the furnace.

Try Our Free Thermostat Repair Quote Request Tool

Tell us some details about your needs and get connected to pre-screened companies in your area. Compare free price quotes from multiple companies and save time and money instantly! No obligations to hire or purchase ever!

Once you’ve confirmed that the furnace is not the problem, there are some things you can do to troubleshoot on your own before calling a repairman. If those don’t work, then it’s time to hire a handyman or HVAC professional to repair or replace the device.


A broken thermostat can cause extreme temperature swings, a furnace that cycles on and off too frequently or a furnace that does not produce...

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I am trying to replace an old Ruud mercury bulb type thermostat with a new Honeywell digital (Home Depot special). The heat pump is a Carrier 38YXA024032, with FX4ANF030 air handler. The new thermostat is a Honeywell RTH7400D.

Here is how the wires were connected, and how I tried to connect them:

Yellow - Y ... Y
Green - G ... G
Pink - E ... E
Red - R ... R (there is a jumper to Rc on the Honeywell)
Blue - B ... C
Orange - O ... O/B
White - W2 ... Aux
Gray - X ... Not connected
Black - L ... Not connected
The Honeywell thermostat also has an L terminal, with nothing landed on it.

From reading elsewhere, I concluded that the X & L wires were only for indicator lamps on the old thermostat, so were not needed on the new one.

When I switch the system on with the new thermostat, with the system mode set to "Cool", hot air comes out of the vents, I can hear the...

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Many people depend on programmable or adjusting thermostat to keep their energy bills under control. However, this can work only if the thermostat functions properly. Otherwise, you will end up with very cold or hot rooms that are uncomfortable to be in and high energy bills as well.

There are many reasons why the thermostat might not be working properly and you need to check for each of these causes before you can fix the thermostat and have a home that is at the right temperature.

1. Do You have Power?

The first thing to check when you encounter a thermostat that does not work is to check if it has power. Just check that all the wires that connect to the thermostat are fixed properly and tightly. This should restore the power supply to the thermostat and ensure that it works again.

2. Keep is Clean

A thermostat needs to be clean in order to work properly. Unscrew the cover of the thermostat and gently clean the wires inside using a...

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When we bought our boat, we received a lot of material from the former owner which included a list of all gear and equipment aboard (including make, model, size, serial number, year of installation, etc.) This included the length and size of e0ery piece of rope and wire aboard, etc. My idea is to provide blank forms on which to enter this sort of thing. Many people who are showing up in TALIS are new to a cruising boat and need to be shown how to perform periodic inspection and main- tenance of engine and rig, etc. But even old hands need somewhere to record model and serial numbers so that they can easily order parts in a hurry.

The editor suggests you have a section on annual maintenance. Note the things that need to be done as you find them. Check them off and note the date when you do them. Three years from now, you will know what year you did which job!


A boat owner is a...

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