Heater won't stay hot?

MMCK1313

MEMBER
2002 CHEVROLET S-10
6 CYL
4WD
AUTOMATIC
78,000 MILES

I have a 2002 chevy s-10 zr-2. I have a problem with my heater that is driving me crazy. I have changed the thermostat and flushed my cooling system. When I first start it, it seems the heater is working fine. The air is very hot. After it comes up to running temp, the heat slowly turns cold. The selector for my vents is not working correctly. It will not switch between face and feet etc. The water going in is hot, the return is cold. Has anyone heard this problem before? I am at my end and need help.

2 Replies

RASMATAZ

MECHANIC
75,992 POSTS

The water going in is hot, the return is cold.

Look for a heater control valve-check for clogging heater hose/s and heater core.

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Sunday, December 16th, 2007 AT 4:20 PM

KEN L

MASTER CERTIFIED MECHANIC
47,690 POSTS

It sounds like you have two problems, the first is the heater core is clogged I would use a garden hose to help flush it out, next I would make sure the vacuum source under the hood that goes to the fire way and the HVAC system is not broken. Please go over this video it will help;

https://www.youtube.com/watch?v=SNRb6pSwYuU&t

Please go over this guide as well for the broken vacuum line.

https://www.2carpros.com/articles/air-vents-stay-in-the-defrost-position

Please go over these guides and get back to us.