Yes, this usually means the coolant isn't able to make it through the core. Both hoses should be hot (or at least warm).

 

Wedging an aspirin in the thermostat will usually hold it open long enough to purge all air from the system. Gotta agree the first place to start is flushing the heater core.

 

well i just fixed this in my work blazer before i came out to Utah. and thank goodness i did. it was cold in Salt Lake City. anyway, i had the same problem, passenger hose was hot and driver was cold. i took the passenger side hose off the engine and put it in an old milk jug, then i took the driver side hose off the heater core and got a piece of 5/8'' hose. (its what i had laying around) put the 5/8 hose on the heater and blew into it gently. it took a couple of times but then i got some fluid out of the other side into the milk jug. full of all kinds of crap. put it all back together and fill with fluid. works better now, but not as hot as my other blazer. it will need a core soon, but not until it leaks. i was down in -15 and still warm and toasty. hopefully you have the same luck.

 

Yup the left hose is the inlet which will be hot and the right hose is the outlet which will be less hot or even cold when the core is plugged. Best to take both hoses off and flush back and forth until the water is clear. Usually have to do it once a year in my Jimmy.

 

Okay everyone here is an update. I finally had my garden hose not frozen and went ahead to reflush my core. Flushed it until both sides came crystal clear with water. Although I didn't see any gunk or debris come out except the dex coolant, my heater works wonderfully hot like my other blazer. (I own 2 blazers 01 & 04) Thanks everyone for your help and information!

 

Cool man, glad you have heat now. I had to flush mine again last weekend and it works excellent now.

 

Yeah man! A complete system flush in the spring should stop the chunks in clogging the core.