RV Repair: What made that noise?, itasca suncruiser, noise question

Question
QUESTION: Hello, I am in a 1995 Itasca Suncruiser which has been parked for some time.  A few minutes ago, I heard a noise I haven't heard before.  It sounded like a motor running and was coming from the kitchen area, around the sink or oven, but I couldn't pinpoint the exact location.  As far as I know, all there is behind that area is the water pump and outlets for grey and black water outside.  It was not the water pump or the driving engine or generator but it was very much an engine or motor like sound.

It stayed on for perhaps two minutes and turned off again.

What might this have been?  I also wonder if it could be related to another unusual sound that has been happening the last couple weeks - a rumbling "boom" that lasts about a second, but seems to be coming more from the back and not the kitchen.  This happens maybe once a day or once every two days.  It's not loud, but it will get your attention.

I hope this is not too confusing.  Thank you.

The motor noise just started again while I was typing this.

ANSWER: sounds like it could be dangerous.  could this be the furnace?  rumbling boom sounds like the sound of a burner in the furnace going bad.  I would have said water pump but you ruled that out.  I am thinking of what turns on and off.  the furnace has a purge motor.  Do you have A/C.  could be A/C coming on but that should be in the roof.  furnace is low.  How about stove exhaust fan?  could this have something to do with the slideout?  

---------- FOLLOW-UP ----------

QUESTION: I hadn't thought of the furnace since it's not used.  There hasn't even been propane in the tank for years*.  I just checked and the heater had somehow been turned on!  I turned it off.  Thank you!

Since I don't use the heater, would the boom still be associated with the furnace?  

*The motor home is parked. I live in it full time and have electricity so I use an electric portable heater

Answer
I thought the rumbling boom was connected with the motor noise.  If so, you may have been hearing the sound of a vent door shutting, or duct work sounds associated with the furnace trying to start.  It could also be noises of mice in the ducts, or something unrelated to the ducts.  I am not sure what is in the rear of your Rv.  Is that a bedroom?  Bathroom?  

Good Luck.