(Truck Info and Situation) Well winter has finally come here to the interior of Alaska. I recently bought a 2002 Cummins quad cab (sig has the details) and this is my first winter up here with it. Last winter I drove around in a 12V extenda cab, it would warm up AND retain the heat just fine. This week we have been dipping down into the -20 temps, and I'm starting to find out just how cold my cab is. First thing I did was change to a 190 T-stat, which kinda helped. Second I threw a piece of cardboard in between the radiator and intercooler. Finally, I activated the 3cyl. high idle to help it warm up in the morning (fully winterized and plugged in, starts like a champ).

(Actual Problem) But I still can't get the cab as warm as I want it, no matter how long I drive. The temp is up to 190 after about 5 min of driving, and I have the blower on full, but the air coming out just isn't as warm as I think it should be I changed my coolant to a 70-30 mix (good to about -70). And when I drained the old stuff it looked really really clean, so I don't really think the heater core could be clogged up. Did these trucks just not have powerful blower motors or big heater cores? Any tricks or upgrades that I could do to get my truck to blow warmer air?

 

Blend door might be hung up and the cores get full of crap that comes in through the cowl, you might have to pull the heater box and clean it. Have fun with that, dash has to come out.

 

the evap core typically gets plugged up full of crap. the heater cores are usually always clean because all of the dirt from the outside has to go through the evap core before it can reach the heater core.

anyway if you want hotter air out of the heater core, you can either turn it on floor heat only which won't run the a/c compressor to dehumidify. or you can change your tstat again to a 200* tstat for a 6.7L cummins. it will fit the 5.9L as they did not change the tstat size at all. it just opens at a warmer temp.

plenty of guys in cold climates such as yourself have changed to the 200* tstat to help the heater core in heating the air coming from the hvac. be surprised what an extra 10* can do...