1999 ECSB Silverado Z-71 ..

5.3l

Getting no heat inside the cab.


Suspect its the thermostat.. The lower Radiator hose
is cool to the touch, whereas the upper rad hose and the hoses to the heater core are warm..

sound right?

Swapped out the control unit that controls the fan speed/ac temp setting with a good one, no change.

Thanks for any input..

is the heater/blower fan working?

Yep..

The blower fan runs at all speeds, the AC works great, no heat.

What temp does the truck run at??

Put another jacket on and dropped a hot pocket in your pants!

Truck runs at normal, does not heat up.

Suspect thermostat has stuck open.

If its runs ok, and it doesnt heat up then Id say your right, get a thermostat for it

Even with a stuck open tstat, its going to warm up. It may not get HOT, but it will be warm. What temp does the truck run at? If the gauge shows near 200, its not your tstat.

Yea, I agree with what BigTex said. You also mentioned that both heater hoses were hot...that would dictate that your heater control valve is working. May have a stuck blend door or siezed blend door actuator.

Has the cooling system been work on lately, you could have an air lock. And is the coolant low at all.