No heat

[Wimpy]

I have an 03 S10 that the heat will not work in. The air conditioning works just fine but if you turn it to heat it just blows cold air. I have replaced the heater core, the thermostat (twice). Just had a new water pump and a new radiator put on. Anyone have any ideas what would cause this?

[wtnhunt]

First thought would have been the heater core, really not much else I would think could be the culprit other than maybe a bad switch. Heater cores are a bit of a pita to get to on an S-10 if I remember right, at least the 90's models were anyway. Had to replace one on a 93 when we had a cold spell where temps were not getting above 20 during daytime, of course that was before I had my garage.

[Shaun_300]

Does the air temperature change at all when you turn the dial to heat? Turn the air flow to face with the A/C off and go from fully cold to fully hot. If it doesn't change at all it could be the HVAC control head itself, could be a temperature door actuator, or the wiring to it.

How long ago did you change the heater core? The S10s are horrible for them clogging up. Especially if the coolant hasn't been flushed in a long time. Let the truck warm up and feel your two heater hoses under the hood, they're the ones going to the firewall. If one is hot and one is cold the heater core is plugged. If they're both hot the heater core isn't plugged. And it's more than likely one of the two I said at first.

[LETMGROW]

Check the vacuum supply to and from the heater control

Lynn

[Cybertech_hound819]

i did this to my 98 s-10 where you two hoses go into the fire wall full them off and switch them. start the truck let it run for a few second. all it does is revers the way the fluid goes threw and if its pluged it usaly gets it moving again