ss10V8, like 20Blazer00 said, your heater core is a full flow item so the fact that one side is cold and the other is hot seems to indicate that there is blockage in your heater core. If your heater core was functioning properly, coolant would flow from one side to the other and there would only be a very slight temperature difference.

medic195, I would flush the entire cooling system instead of just the heater core. There are basically two ways you can flush your system. The first way is to open the drain plug in the bottom of the radiator and sticking a garden hose on the top and allowing water to flow throught the system. Start the truck and turn the heat on full blast to flush the heater core. Do this until you have nice clean water coming out of the drain plug. If the buildup is really bad, then you'll have to disconnect the heater core hoses and flush those directly. This method works pretty good but does not completely clean a very contaminated system. I've heard people having better success with a reverse flush. This would entail purchasing a kit that has the neccesary fittings or fabricating one so you can flush the system through the radiator hose.

I would also buy a new radiator cap after the flush as the stock ones are notorious for allowing air in the system. If you are still running dexcool, air is your enemy.

 

I have a similar problem with my Ā“99 LT 4wd with automatic climate control - only that I cant shut the heat off ! This happened suddenly from one day to the other.
Checked the controls yesterday, direction flaps seems to work, air is coming out where itĀ“s supposed to, the fan is working at all speeds. The weird thing is that when I turn the heat control from cold to hot and back to cold something goes on with the vacuum and relocates the air flow?? Any ideas? Could it be the heat control **** itself that needs replacing or...? I also checked all fuses - nothing wrong there either. No traces of transm. oil in the vacuum line to the actuator behind the glove comp. It was the easiest one to check, outside in the dark vinter evening

Another thing, I have the 236 transfer caseas far as I know (4 button AWD) and when checking the vacuum hosesI couldnĀ“t find the three prong connector (as shown in other threads) by the shift motor orany valve contact? I only saw one hose and no valve...? I think that that hose is the same one that comes up along with the transmission dipstick and has a spongy thing mounted on the end. Is this right or have I missed something...?

 

I'm having kind of the same problem. The heat keeps cycling from cold to hot. When I turn the key on I can hear something switching under dash, it sounds like a door is moving also. It keeps moving about every 10 seconds and it doesn't matter what I have the fan or temp **** set to, it won't stop unless I turn the key off.

I removed the control module (the automatic climate control in the dash with the 3 ***** on it) and it stops completely which obviously the hvac doesn't work anymore. This module has also been replaced last year whenever it continuosly keep blowing hot air. Do you think that it has gone bad again? Where can I get one? How much does it cost? I will try to find the receipt.

 

Hi

I have notice something. The heat work only when i'm driving on the highway. So when i decelerate the heat stop.

Get back to me.

Thanks

 

tidoux01, when you turn the fan on full blast, can you feel air (hot or cold) blowing through the vents when you are not moving? Almost sounds like your blower motor is not turning on. If you are driving on the highway, you will still feel heat coming out of the vents with a non functional blower motor because air is being forced into the HVAC system. If that is the case, check the fuses for your blower motor.

If infact your blower motor is working, check if you can control the vents. I had a friend that had air blowing out of all the vents regradless of what setting was turned on the ****. His problem was caused by a vacuum leak on one of the hoses that controled the vents. It could be possible that the dampers on yours are jammed, although I think by default they are supposed to be all open.

 

i have a 2000 Blazer LS. I've changed the thermostat, had no heat after that, so i flushed the heater core and i got my heat back. my radiator had a leak so i replaced it. lost my heat again. flushed the heater core and got my heat back. my intake manifold was leaking, so i put a new gasket in that. ive done an intake manifold gasket on an S10 truck with the same motor as mine. everytime i did something with the cooling system, ive flushed the heater core. air gets in the system pretty easily. youll see two heater hoses going into the fire wall, closer to the drivers side. disconnect them and run a hose through one side and let it come out of the other side. youll probably see dirty water come out. wait until its clean and reconnect the lines. you guys may have a different problem but its worth a try.

 

I just did a coolant change.. they flushed the system but did not take the hoses off the firewall leading to the heatercore.. if I disconnect these, will I loose alot of coolant or?

 

You will lose some coolant but not much. Just use a hose with a little pressure but not too much pressure. Just a regular hose that you connect to your house or whatever. One hose is coming from the water pump, disonnect it from the water pump, and disconnect the second hose from the fire wall for easier access, run the water through the hose from the water pump. and i think i said the hoses were on the driver side of the firewall but that was my mistake they should be on the passenger side of the firewall. After you do that, and you have your hoses reconnected, start your truck and turn the heat on. Top off coolant.

 

Your the man..

 

Did it work?