My heater on my 3.1 td grand cherokee jeep has gone cold?

Hi I have a 2002 JGC ltd and it is most likely your dampeners or louvers located behind your temp controls (inside the dash) for driver and passenger sides that control the direction of air flow from air outside in, circulation, heat to windshield, centre and or to floor etc. I had a friend that had heat only to the passenger side and cold air blowing to driver side. He took it in and they replaced stuck dampeners and it was not cheap. Sounds like the tipical problem with heaters.

Jeep Grand Cherokee is notorious for broken blend-air doors. This is the door inside the A/C-heater housing that switches the air from hot to cold. You must remove the dash to repair it.

Try spraying some WD-40 on all of the linkage points - inside out. It's obviously a linkage problem. The cold may very well be a factor.

Check the thermastat or your cooling fan to make sure all is working good. If your engine cant warm up, you will not produce any heat inside the car

It could be the security system or maybe a crank sensor.

hi
the blend doors are located behind the glovebox were you will find the heater box the doors are inside this, to remove the heater box you will have to take out the complete dash. try heatertreater.net they have a diy easy fix solution to replace damaged or broken blend doors, i have fitted a few off these kits all work fine with no problems..
hope this helps

It could be the thermostat or a plugged heater core. Check hoses going in to firewall after the vehicle has reached operating temperature for a drastic change in temperature if one hose is hot and the other cold or just warm your heater core could be plugged and would need to be flushed.

replace the heater resister pack

Change your Thermostat.

Heat adjuster door fix does not have to cost a lot of money. Search for Heater Treater. I lost dual control functionality but it is way better than the $1800 the dealer wanted to charge me.