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Gary, Chevy Technician
Category: Chevy
Satisfied Customers: 17157
Experience:  15 years GM master tech
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My 2003 s10 PU heater is not working. Changed bad thermostat

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My 2003 s10 PU heater is not working. Changed bad thermostat but still not working. When I turn the temp control knob it does not feel like it is moving anything. Could the actuators be the problem?
JA: Sometimes things that you think will be really complicated end up being easy to fix with a Chevy. The Chevy Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so he can help you best.
Customer: A few months ago the heater would not work. I noticed the coolant was low, subsequently found leak. I added coolant and the heater worked. Eventually the leak, inport manifold gasket was replaced along with the thermostat and serpentine belt. Now the engine is running at the right temp but the heater only blows cold air.
JA: Leaks can get messy. The Chevy Mechanic will know what to do. Are you hoping to fix this yourself?
Customer: Yes. I thought I would start with simple like the blend door actuator.
JA: Great! What have you tried so far?
Customer: Nothing yet
JA: Is there anything else important you think the Chevy Mechanic should know about your Chevy?
Customer: Every now and then I think I hear a hissing sound like an air bleed but it only lasts for a second.
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Chevy Mechanic about your situation and then connect you two.

what size engine is in this truck ?

the blower motor is working fine on all speeds ?

when the engine is warn feeling both heater hoses are both very hot ?

Customer: replied 1 year ago.
4.3 L V6
Blower works at all speeds
Haven't checked the heater hoses.
Customer: replied 1 year ago.
I am warming up engine now to check hoses

also when the truck is running and the engine is warm if you listen close when you turn it from hot to cold do you hear any doors move or even feel the air change at all in temp ?

Customer: replied 1 year ago.
The hose on the left (passenger side) is hot. Hose on right is lukewarm. With fan blowing on high (number 4) I can hear and feel the vents open and close from defrost to feet to upper body and so on. Also noted that when I turn the temp control (not Automatic) from cold to hot the extreme cold blows harder than the warm to hot settting. Still no change in temp though.

ok most of these types of issues are restricted heater codes

remove both heater hoses and with a garden hose back flush the heater core side to side with the hose nozzle good until clear water is seen passing though bot flush ways

put the hoses back on and see if the heat comes back

the odds are it will as these heater cores had an issue of them plugging up

Customer: replied 1 year ago.
I do this without removing the core? The water does not leak into the cockpit?

yes right under the hood at the fire wall

Customer: replied 1 year ago.
Excellent! Thank you.


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