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Thank you, I will look into that

It could be a "chattering" relay on the furnace control board.  If you disconnect the G wire from the furnace does this still happen?

If so I would look at replacing the control board, and explain to the client that likely a dirty filter caused the furnace to cycle on limit and that eventually wore out the old relay due to all the excessive starting and stopping.

Good morning,
I was recently called to diagnose an older Carrier furnace that was short cycling, I found the cause to be a dirty filter and replaced it. I checked everything else and performed maintenance on it and all seemed good to go.
I got a call back and the furnace is working but after it's satisfied on heating, the blower will disengage and immediately turn back on for a second, tested everything I felt might be the problem and all looks good but it's still happening.
Any suggestions on what it might be are appreciated.

thanks!  I will definitely try that.  seems I blew the fuse in the 155MAX and will try again once I source a new one.

Gemini chatbot suggested this is the wiring:

Color Function Terminal #
RED 12V Power 3
ORANGE ON (Control Signal) 2
GREEN LOW (Low Speed) 1
YELLOW HI (High Speed) 6
BLACK COMMON 10

and suggested I jumper red to orange, and then connect acc+ to orange, and ACC- to either green (for low speed) or yellow (for high speed).

I'll report back on which wiring yields the correct result in case others are curious.  I'll make sure I have a few fuses just in case!

I couldn't even see the terminals in the above picture, so thank you for listing them!

I would jumper BLK and RED on the HRV, and if the HRV starts those are the 2 wires to connect to the Ecobee ACC terminals.  The other wires would not be needed.

See the wiring diagram below.  The Ecobee would be considered a toggle switch (dry contacts)

Quote from: Admin on October 21, 2025, 08:27:56 PMYou need to follow the mecanical timer wiring.  See the attached picture.  Install a jumper between ON and RED.  Then wire the Ecobee ACC wires to HI and ON.  The HRV will run in high speed when it's turned on.  You could also use low speed instead.  Just connect the ACC wire to LOW instead of HI.  The Ecobee can only control one speed and not both.

hey there, sorry to jump on a thread that isn't mine but I have the exact same issue and am not sure that the response answers the question.   Like the OP I have a 5 terminal block on the outside of my 155MAX that runs up to a controller with dehumidistat dial next to my thermostat.   the 5 wires are labeled "BLK, RED, ORG, GRN, YLW".  in my existing setup the orange terminal is not connected, the other 4 wires run upstairs.

in your response you have a 10-terminal block which I'm guessing is from newer HRVs?  I definitely don't have that on mine and I'm guessing OP doesn't either as my situation matches his pictures.

Given that there is no ON or HIGH or LOW or any of that.. is there a known solution for which two of those color coded wires from the 155MAX become ACC+ and ACC-?

Hello all, I just joined this group because my heat went out last night and its 15 degrees here.  I woke up this morning freezing and discovered the thermostat read 55 degrees.  I checked the breaker and it was kicked, so I reset it and turned on the heat again at the thermostat.  It paused a second, which is usual, then acted like it was going to start, then CLICK, the breaker tripped again.  I tried this several times and did the same.  My outside unit had ice caked on the grill on top, which protected the big fan motor on top, so I cleared the ice.  I also noticed there was ice below the fan inside the unit. My question is, can the interior blower motor actually freeze up while it's running?  During this cold spell it has been running constantly.  And I don't think it's a capacitor since it tried to start...if the capacitor blew it wouldn't have the power to try to start, is this correct?  Any advice is much appreciated.  Thanks!   

Download the TSSA Media Release - Here

QuoteToronto, ON, January 29, 2026 — Red Cap Propane has been fined $45,000, plus 25% victim surcharge, by the Ontario Court of Justice after being found guilty of a fuel safety violation under the Technical Standards and Safety Act, 2000.

In February 2024, an explosion occurred at a residence in Cambridge, Ontario, which was serviced by Red Cap Propane. The home has since been deemed uninhabitable and was recommended to be demolished.

TSSA's investigation determined that the incident was caused by a faulty connection from the home's propane tank to its furnace, which allowed significant amounts of propane to build up underground.

The homeowner had previously raised concerns about unusually high propane consumption even during summer, with the furnace being the only propane powered appliance on the property. In July 2021, Red Cap Propane conducted an inspection in response to the customer's request and relocated the propane tank on the property. The company dispatched a subcontracted senior gas fitter in November 2022 to conduct a pressure test. The subcontractor, however, incorrectly determined that no leak was present. TSSA's investigation found that issues with the connection between the tank and the gas pipeline contributed to the leak and the subsequent explosion.

TSSA also discovered that the gas regulator from the site had been removed by an employee of Red Cap Propane, contrary to the Technical Standards and Safety Act, 2000, which prohibits interference with a gas incident scene until TSSA releases it.

Owen Kennedy, TSSA's Director of Fuel Safety Program, said, "Ontario families count on fuel contractors to meet regulatory requirements and keep them safe. When it comes to fuel safety, there can be no compromise. Equipment must be installed, inspected, and tested with care and professionalism, because even a single oversight can have serious consequences for life and property.

This case also reinforces a key legal requirement that all equipment involved in an incident is evidence and must not be removed until TSSA has released the site. Preserving the integrity of that evidence is essential, not only as a legal obligation, but also to ensure that our investigation can accurately determine the cause of incident, responsibilities of the parties involved, and prevent future incidents."

I would expect the pressure switch or even rollout switch to open before the primary limit, if in fact the inducer motor is the problem.

I would check second stage gas pressure and temperature rise.  It sounds like the motor will need to be replaced.