How do you know the amount of ohms a blower motor is suppose to have when the manufactor doesn't put it on the nameplate of the motor ?
is there like a rule of thumb for the ohms on the motors ?
Like there is for a 3 phase motor, I know that the ohms should be all equal or close to equal for the ohm test for each line
and for a perment split motors its R-C should be low, S-C should be second highest, R-S should be the highest and that R-C & S-C should add up to R-S
I m still newbie to the hvac industry, and trying to learn about troubleshooting
I've used that method to test the windings on a compressor. I wouldn't worry about doing that on a PSC motor. Test your capacitor if there is one. Measure your Amps while the motor is running. Spin the blower wheel with your hand when the power is off. You'll know when the bearings are beginning to sieze up, and listen to the motor during startup. You can usually predict when a motor is about to fail.
If you're working on a 12 year old + furnace, and you're doing a maintenance, just advise the client the motor may fail. Offer them the repair to be proactive, or if they decide to risk it and wait for failure they won't have hurt feelings when it does. The 12 yr old PSC motors that are run continuously, sometimes may fail shortly after a service call, when you remove them to wash out the blower assembly. The windings are so hot and old that when they finally cool they crack, or begin to wear.
Thx for the advice
A few guys at the supply shop say if your doing regular maintaince they told me to its a good idea to take the ohms on motors when their new and write them down on the unit inner door. Most of them agreed that when a motor starts to age, its could go anytime.