Jimmy won't heat up?

is the blend door working properly?

yea likly also on that old of a vehicle it is also actuated by vacume i belive make sure you check all vacume connections at firewall also

check hoses at firewall in and out of core are both hot?

That one actually uses a cable to control temp. If both heater hoses are hot, then check the cable. If both hoses are not hot, then you could have a plugged core or engine temp problem.

Is that located behind the glove box?

It's attached to the control head itself. Follow it to the blend door.

I'm confused...where is it?

It's attached to the back of the control that you are trying to control the heat with.

so how do I check if it works properly?

yah behind glove box. if you put it to cold does heat stop coming out? and what did you mean when you said you replaced "climate control"?

I replaced the controls for the heat/air conditioning. The one that controls the temp and fan speed etc...

do you have S10 or full size?

I have a 4 door 4.3l sle

so have you checked blend door travel to see if it's hitting both stops? opening and closing completely?

I'm gonna try it when I get home from work

there could be an obstruction in the exit of the water pump which "powers" the heater core. You said it is a new core. Try flushing the core anyway, in hopes to flush out the pump in the process. I've seen it in a suburban before, different vehicle I know, but same concept. Flush the waterpump by itself if you can.