Hi I have a 2000 jeep cherokee and when its cold out and I start the jeep if I turn the heater on to past 1 a loud squeling sound comes from the pullys or belt and it gets louder with higher rpms if I don't shut the heat off while it's doing this a check gauge light come on and the gas, battery,oil pressure, and temp gauge stop working but the rpm gauge and speedometer still work and idk what could be wrong

 

Check the age of the belt. Look for cracks and make sure it's tight and not loose. As for your gauges not working, it's prob an electrical short somewhere.

 

Might be the bearings in you tensioner or idler pully. i would use WD-40 or PB as a temporary fix. just my opinion.