Furnace Wiring Diagram

Gas furnaces go by era. These range from gas conversions of coal furnaces, gravity furnaces with no motors at all, to sophisticated two-speed gas furnaces with variable speed DC blowers for house air circulation. The furnace I got last year, you "set the motor speed with your iPhone" :-/ Which sucks. As using controller board jumpers is the more intelligent choice.

Motors for circulating warm air through the house, come in one speed and four speed types. the four speed might have five wires. The wires are brought up to the controller board, and the user can move a single jumper, through one of four positions, to set the motor speed. The motor speed is set via a Delta-T measurement. You check the inlet temperature with one thermometer, you check the hot air from the furnace a couple feet on the hot side of the furnace. The plate covering the goods inside the furnace, has a specification printed on it

35C < delta-T < 65C

as you can crack the condenser on a furnace, by using the wrong speed on the circulation motor. The furnaces with single speed motors are generally "iron hulk" condensers and they are less likely to need careful treatment, like the miserable modern furnaces (high efficiency condensing furnaces).

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Let's ask the LLM AI.

Copilot question:

Do you know of a Clare Brothers G126 LB-M gas furnace from Canada ? The owner is looking for a wiring diagram or other information. The company may have been acquired by another heating firm, the Clare Brothers being a small OEM, building furnaces rather than being a major manufacturer like a Goodman.

Copilot answer:

**Direct answer:** The Clare Brothers G126 LB‑M gas furnace is a discontinued Canadian model. Clare Brothers was a small OEM that was eventually acquired by *International Comfort Products (ICP)* in 1999, which itself is part of Carrier/United Technologies. Wiring diagrams for specific Clare models like the G126 LB‑M are not widely available online, but general furnace wiring guides and parts support can still be found through ICP or suppliers such as AMRE Supply.

### Background on Clare Brothers

- **Founded:** Clare Brothers Limited was incorporated in 1903 in Cambridge, Ontario.

- **Products:** They manufactured oil and gas furnaces, boilers, and heating equipment.

- **Acquisition:** In 1999, Clare Brothers was acquired by *International Comfort Products (ICP)*, which is owned by Carrier (United Technologies).

- **After acquisition:** ICP discontinued the Clare brand, but parts and service information are sometimes still available through ICP or third‑party suppliers.

### Wiring Information

- **Model-specific diagrams:** The G126 LB‑M diagram is not directly published online. However, Clare furnaces often used standard wiring layouts similar to other forced‑air gas furnaces of the 1980s–1990s.

- **General resources:** - [Basic gas furnace wiring diagram guide]

explains the control board, ignition, blower motor, and thermostat connections.

- [Step‑by‑step furnace wiring instructions]

provide safe wiring practices for older furnaces.

- Expert Q&A forums (like JustAnswer) have discussions on Clare Brothers wiring, where technicians walk through connections for discontinued models.

### Parts & Support

- **AMRE Supply** and **Temperature Supply** still list replacement parts for Clare furnaces.

- ICP can be contacted directly for legacy documentation or service guidance.

- Common replacement parts include ignitors, blower motors, and Honeywell control modules.

### Practical Notes

- Because Clare Brothers furnaces are long discontinued, **official wiring diagrams may only exist in archived service manuals**.

- If the owner is troubleshooting wiring, it’s best to compare with **generic gas furnace wiring schematics** (thermostat -> control board -> gas valve -> blower motor).

- For safety, wiring repairs should be confirmed against the furnace’s voltage and control specifications, ideally by a licensed HVAC technician.

Would you like me to **track down archived Clare Brothers service manuals** (sometimes available through ICP or collector forums) so you can get the exact G126 LB‑M wiring diagram?

Cites:

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The HVAC industry is a crooked one. If you invite any sort of technician into the house, they will condemn the furnace and red tag it. A red tagged furnace, can even have the gas supply cut off to the house, as the gas supplier does not want condemned equipment connected to the gas network. (You get a fixed number of days to effect a repair and bring the furnace back into safe operation so the tag can be removed.)

As an example, I had a furnace condemned, I asked the fine gentleman to show me a CO reading showing the chamber was cracked and he said "oh, I don't seem to be getting a CO reading here from the side of the machine". The machine went on to heat for *another 20 years* before it actually cracked and set off my CO detector. Given the age of the unit (1990s), that will be a one speed Honeywell gas valve, it could be a spark type ignition (rather than the hot plate type of today), and the motor could be a one speed motor. The wiring in such a case should be pretty ordinary. The motor needs some drops of oil in the two oil ports, once a year. Modern motors don't have oil ports. The 1990s furnaces need little in the way of maintenance, oil the motor, vacuum out the burner assembly to remove crud.

The purpose of having a four speed motor for household air circulation, is for setting the motor speed via four jumpers on the controller board. When the furnace is used for "call-for-heat" as well as "call-for-cool" on whole house air conditioning, there are relays on the controller board, that in effect "sample" the motor speed setting from the "summer" jumpers versus "sample" the motor speed setting from the "winter" jumpers. They could have set the motor speed via wire nuts. The motor in such a case might have five wires or so. Thus, if it's a multi-speed, expect more wires.

A single speed motor, implies chamber temperature is less critical or can be adjusted by using the dampers in the air circulation (plenum) so that the chamber runs warmer or cooler and meets whatever passes for a delta-T measurement. More modern gas furnaces, the cover plate comes off at the bottom, and on the plate it says

35C < delta-T < 65C

And then you select a motor speed, so that the difference across the furnace meets that spec. Usually, only the top two of the motor speeds are used, so you don't really have four adjustments and only two of them are expected to be useful. The summer setting might be "one from top", the winter setting "flat out" subject to verifying delta-t on the cover plate is met.

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You can see here (oh, the comedy), that the four speed motor on this one, only the High and Medium High are wired up! The Medium Low and Low are not wired. You will need a modern browser to get round the cloudflare or other, protections.

The "volt board" lower left, that goes to the five wire cable leading to the thermostat. That's enough wires for "call-for-heat", "call-for-cool", and "circulate" which just moves air through the house without thermal input. For a heating only application, less than five wires are needed to make it work. The "transformer" uses low voltage for "sense" of switch positions on the remote thermostat. There are also thermostats with more than five wires, requiring that you pull another cable to the thing, to fit such a (fancy) thermostat with day-of-week setup. The five wire interface, "power is implicit" in that the thermostat closing a switch triggers the thing and there is no accessory power for the thermostat. If the thermostat is to receive accessory power, that's when a seven or eight wire bundle might be pulled up to the thermostat in the middle of the house.

Paul

Thanks Paul,

My advice was to get someone in but this is his worry

"The HVAC industry is a crooked one. If you invite any sort of technician >into the house, they will condemn the furnace and red tag it. A red tagged >furnace, can even have the gas supply cut off to the house, as the gas >supplier does not want condemned equipment connected to the gas network. >(You get a fixed number of days to effect a repair and bring the >furnace back into safe operation so the tag can be removed.)

It seems there are lot of these old systems in Canada still working after several decades. I manage to help him track down a replacement motor . I looked like the centrifugal switch had failed

He sent me pictures of the name plate and parts; there doesn't seem to be much in it

Cheers

Brian