Clogged heater or just not hot enough?

My car is a southern car, it has the tow package and a low temp thermostat in it.

The engine barely gets warm even on long drives, probably because of the tow package engine fan, and the radiator with fan, and the low temp thermostat.

I drove it for an hour last week and it got about 1/3 the way up the temp dial, put the fan on heat and nothing.

Not even warmish air.

So you think the heater core is clogged? What's an easy way to flush it?

I would say the heater core is plugged, very common. Feel the both hoses going to the heater. Both should be hot. If one is cold, it's plugged. I would disconnect the hoses at the plastic "T" and the reducing valve. Get a hose adapter so you can connect the garden hose to the heater hoses......and then reverse the hose to flush both ways.

Tom

Although I'd agree a plugged core is the most likely culprit, another possibility is that the cable connected to the temperature lever isn't throwing far enough. It operates the "mix" door inside the heater to regulate the temperature via diversion of the air flow though the heated core.

It's relatively easy to check.

 Dave,

I went to the local parts shop and they have nos ac delco heater cores for the car for $60, he had two and said he'd give me both of them for $80. This is a cop shop with a good amount of 9c1 parts left.

Should I snap those up? Will they last in storage or will the aluminum get bad after a while?

I believe the cores are brass (99.99% chance). If you keep them dry, they should last forever. Check the cores for leaks, and if they do leak, you can resolder them if they are brass. To check for leaks, hold one line closed with your finger or thumb, and blow into the other. If it does not hold pressure, putting water in it will show exactly where the leak is. To solder it get some resin flux, and some plumbers solder. A propane torch will get it hot enough. Do not use acid flux under any circumstances. If it is aluminum, there is aluminum solder with special flux in it. The propane torch is sufficient for either metal. The aluminum dissipates heat faster than the brass, so be careful if it is aluminum, because you can unsolder the good parts.
 
You did not state if you have manual or automatic climate control. The automatic climate control uses vacuum to move the diverters.