Moved into a new (to us) home this summer with 2 split systems. One is a couple of years old and the other is the original system(22yr old Carrier).

The old Carrier system has an inducer motor that is going bad and a couple of times the furnace has failed to ignite causing a couple of pretty cold nights as this system serves the master bedroom.

My question is this: If the furnace is operating and the inducer motor quits, will the furnace shut itself off automatically? Obviously worried about CO not being vented in this instance. We do have new CO detectors and none have ever alarmed. Just want to be able to sleep with some peace of mind that we will wake up in the morning.

TIA

A typical furnace has a sensor that looks for negative pressure that the draft inducer motor creates. That sensor is an interlock for the gas valve and ignitor sequence. I believe it should also shut it down if it loses negative pressure. I'd fix it, but I wouldn't worry too much about CO, especially if your CO detectors in the house are working.

Have you tried cleaning the flame sensor ?

22 years is getting up there in age for burners.
Have you had them professionally inspected for cracking?

I'm having this issue as well on a Frigidaire furnace. From what I can tell, it's probably the flame sensor. I'm going to have someone come out Friday to poke around at it and hope that fixes it.

I've had service guys out and the inducer motor is their diagnosis. Was just worried about running the system while we wait for the part.

Yes. There is a proving switch for the inducer motor. If the switch is stuck the heater won't come on, if the fan fails mid operation the switch opens and shuts the heater. It's a little black pressure switch with a hose that goes to the heat exchanger to verify negative pressure. If the draft motor fails while running and the pressure switch doesn't open there are limit switches mounted that should trip due to the exhaust gasses adding heat to the system. If that doesn't work I wish you the best.
Overall it's a fail safe design that's been tested and proven for over thirty years. The quality of pressure switches leaves a lot to be desired for in the new ones for sure.
Always good to check you CO detectors for their expiration date as well as batteries.