Heater not hot

number of possibilites for no heat.

1. Your engine thermostat is broken and stuck in the on possistion. In the winter months, if its stuck in the open posistion, the vehicle may never get warm enough for the heater to blow hot air (i had this problem once, 13 degrees outside and even tho we had been driving for an hour, not a single bit of warm air... fixed instantly with new thermostat) this is a cheap repair

2. you have a clogged/broken or something has happened to your heater core, it is located in the dash somewhere and hot coolant flows into it. This is not terribly expensive, but labor cost may be a bit high, sometimes there not easy to get to

3. and least likely is that your heater door wont open. Does your a/c still work fine? if yes, if you leave the ac on, and turn it from cold to hot, does it stay exactly same temp or cold? or slightly warmer? if it stays the exact same tempature of cold and you cant tell that anytinh has changed, the door that closes the ac and opens to heater could be stuck/broken, etc. or the cable or electric wire controlling it could be bad..

that concludes 3 reasons you could be without heat, as far as your electrical goes, I would make sure all your fuses are in good, otherwise, who knows, electrical in cars is a whole nother ball game

Sounds like it is low on Antifreeze or the thermostat is hanging up. This would account for the lack of heat, which should be felt in the water lines coming out of the heater core.

Both water hoses should be equally hot if the heater is on full blast. But there is a radiator cooling fan for the engine and it is to some degree responsibile for cooling the water. But even at 180, you would have heat.

Last, as this is 13 years old, check for collapsing main radiator hoses.

160 degrees should be hot enough to get some heat.
You could check the engine temp with a scanner to confirm.
I would double check the blend doors, and the temp of the coolant in and out of the heater core. I use an inferred temp gun.

Hi John,
Your right with your diagnostics, you have a blend door problem. If your switching to cool air and it is still hot then you also have a heat exchange unit fault, this is the component that changes the water flow from hot to cool by shutting off. If it is not operating correctly this will give you constant hot air no matter where you temperature switch is positioned.
As for the warm air while the engine is cold, sounds like the blend door is still open to atmosphere tempreture and if it is hot outside will pull that hot air into the inside of the vehicle.
Have the heat exchange valve checked, and the only way the check blend door operation is to remove the wiring from the blend doors and have the circuit tested. If the circuit is ok then the blend doors will need to be replaced.
Hope this helps

if you have 20 degrees difference that is quite a bit of a difference.i would say that the heater core is plugging up,remember the fan blowing air across the core is cooling the temp more and with a 20 degree difference its alot.you can try to run CLR through it a couple of times to see if it will help flush out more dirt.sometimes flushing just doesn`t do it.

check the coolant hoses going into the heater core. they are the hoses running through the firewall under the hood. if they are both hot, you way have a heater core blockage. a heater core flush should solve this. if it does, you should follow up with a complete cooling system flush.

that year / series of GM sonoma and s-10 where famous for having clogged heater cores - is temp of hoses going in and out the same ? if not try to flush out ther core, if they are, ck to see if the hot water valve is woking, and finally operation of the doors inside the heater box itself

try changing the thermostat if thats not it check and see if you have water leaking in the passenger side floor board if so then you need a new heater core

set temp to max 32degrees will turn on the a\c
2. check the fuse for cruise

switch prolly not bad but you might wanna look into your heater control valve. valve not closing and letting the hot coolant fill your heat exchanger rather than recycling it back to the cooling system. The heat is over powering your a/c system and you're only getting a bit of cooling when you have the a/c on max. try it out