70 year olf natural gas furnace - 100,000 btu won' start - replaced thermocouple - still won't Repair guy suggests pilot safety valve.. Honeywell... ???

[b]My furnace blower motor started to work intermittently recently. If it starts, it would run fine for several hours. But most of the time it could not start right away. The motor is a ECM motor. I tested the low voltage and high voltage to the motor on the control board when the motor was not working. I can measure AC24V and AC110V. So the control board is fine.I took out the motor and also measured the windings, they all measured around 4.9 ohm and open to the chassis(insulation is good) . The motor itself seems fine. The problem is the motor module. [img]https://u.cubeupload.com/policeman0077/4f2Snipaste202211091204.png[/img] I read online some say the thermistor might be the problem. Although I don't think it would be a easy fix like that in my case, because my motor works intermittently. If the in-rush current protection thermistor burnt, the motor shouldn't run. But anyway I gave it a try. The thermistor measured 1.5ohm at around 15-20 degree Celsius which seems fine. Since I already opened motor, I shorted the thermistor with some thick wire and put the motor back. It still work intermittently and most of the time it won't start. Then I contacted a local furnace technician, he gave me a quote of $1030 of the motor plus installation and tax. It’s a really hard pill to swallow considering the motor itself it good, the only broken part is the control module. That’s a little history which leads me here. Now my new plan it convert the original 3-speed ECM motor to a PSC motor. I google a bit, there are a lot of tutorial online showing how to convert a single speed motor but nothing about a 3-speed system. The following a wiring diagram: [img]https://u.cubeupload.com/policeman0077/Snipaste202211091149.png[/img] Does anyone have similar experience know this would work or not? One of my concern is, I don’t know if the control board would send say high speed and fan speed 24vac signal at same time. This might not be a problem for ECM motor because they are all low voltage signals. But for a PSC motor, turning on two 24VAC fan speed control signal means the relays would energized two windings in the motor at same time. I guess it would not be good for the motor.:wall: Here is the specification of the original motor: Brand: Broad Ocean Model: 1185966 Power: 3/4 HP Voltage: 110VAC Current: 8.8A Diameter: 5 5/8 inch Shaft diameter: 1/2 inch Shaft length: 4 inch Mount bolt circle diameter: 10inch(9.5?) [img]https://u.cubeupload.com/policeman0077/Snipaste202211091204.png[/img] [img]https://u.cubeupload.com/policeman0077/945Snipaste202211091204.png[/img] [img]https://u.cubeupload.com/policeman0077/adfSnipaste202211091204.png[/img][img]https://u.cubeupload.com/policeman0077/1f8Snipaste202211091205.png[/img] [img]https://u.cubeupload.com/policeman0077/c84Snipaste202211091205.png[/img] If the wiring diagram above would work I would purchase following motor and mount: This motor has same power, shaft size and diameter. The RPM is also similar. [img]https://u.cubeupload.com/policeman0077/Snipaste202211091217.png[/img] This is the only 4-prong motor mount I could found on Grainger Canada. Anyone know if the mounting bolt circle is 10inch? [img]https://u.cubeupload.com/policeman0077/Snipaste202211091218.png[/img] Thank you for reading through my post and have a good day![/b]