Just bought a '99 Cherokee and working through its issues. The air blows cold, but there is no heat to be had. Looked at the blender door. I took off the motor for the blender motor and I was able to move it freely by hand. The motor did move (slowly) when I switched the temp from cold to hot, but I replaced the motor anyways because there was some corrosion on the motor spindle and it appeared to move pretty slowly. Despite replacing this motor, it made no difference to the lack of heat. What should I look at next? Water pump seems to be OK because its not overheating. Could it be a blockage to the heater core or is the heater core toast?

 

Reverse flush the heater core. There could be other causes but that fixed the same problem on mine.

 

That was going to be my next step, but every video that I’ve seen has a different method in doing it. Do you have a link on the best method to do the flush?

 

By lack of a better picture, see below.
you'll use the two smaller diameter hoses.

Disconnect both, one from the thermostat housing and the other from the water pump.

Put your garden hose on the one attached to the water pump to 'reverse' flush the heater core. Put the other in a container to collect the crud.

 

+1 give this a shot. And keep flushing for a while. My cooling system was absolutely massacred. The PO did an engine swap and I think the previous motor melted down. Cooling system was absolutely gunked to the max with head gasket sealer and rust. Heater core was completely clogged.

 

With your engine up to temp, you can carefully feel the heater hoses. Both should be hot.

 

You help is much appreciated! I’ve ordered some coolant descaling solution and will try to revive my heater core.

 

Think you'll have more effect from reverse flushing your heater core...

 

I had the same issue, the other posters were 100% correct about reverse flushing, but after that put the lower hose in a pail and raise the other hose and start pouring in CLR till it just starts coming out of the hose in the pail. Raise the hose in the pail to the same height as the one you’re pouring in and fill the heater core with pure CLR and strap them up. Leave it in there over night then back flush it with water again. It will blow heat like new again!!

 

I was finally able to get to this little project yesterday. I bought the $4 plastic flush kit and hooked up the heater core hose to my garden hose and just cracked it enough to get water flowing. First gallon came back really dirty and then v=clogged the heater core despite doing the reverse flush! I was able to get 50cc of radiator cleaner in there and after 10 minutes was able to get flowing again. Took about 8 gallons before it ran clear. Purged the system with 50/50 antifreeze and hooked it back up. Did the trick and now have good hot air coming out of the box. Thanks to everyone for their help!

 

I love a happy ending!! <snif!>