99 blazer heating problems

I have a 99 blazer that the heat isn't getting hot enough. i have the temp set to max 82, fan max and push the button to circulate in the vehicle. Still it is just enough to take chill off. I have noticed that when i go up hills that the cool air will come out of the vents and then warm air will start to come out when i go down the hill. My husband has flushed the heater core 3 times, he also flushed the radiator,replaced thermostat and water pump. also when i have the control on the feet the air comes out of the defrost. i know there is something wrong with my heat but hubby can't figure it out. I smell anitfreeze in the vehicle, i was told that my intake manifold gasket is bad and asked hubby if that could cause problem with heat but answer was no. so i am asking you guys for some help. I also think there is a problem with the dial controls on the dash.

If losing heat on a pull it points to weak vacuum or vacuum leak or a bad vacuum reserve tank or check valve.
The first thing would be to check for good vacuum from engine to heater controls.
If you can smell anti freeze inside be careful.
It is a health hazard to breath antifreeze fumes.
Check that heater core for leakage.
MT

I know this is a dumb question but I am tired of waiting on my husband to fix this. how do I check the good vacuum from engine to heater controls and check for the heater core leakage?

thanks becky

I know this is a dumb question but I am tired of waiting on my husband to fix this. how do I check the good vacuum from engine to heater controls and check for the heater core leakage?

thanks becky

To check for good vacuum you will need a vacuum gauge and find the main vacuum line that supplies vacuum to the heater controls.
It should have 18-20 lbs of vacuum on it from engine.
Some place between the engine and heater controls there is a check valve and most of the time a small reserve vacuum tank.
The reserve tank holds a vacuum supply check valve keeps vacuum on the heater control even when the engine is under load or no vacuum.
Look and listen for vacuum leaks and bad vacuum hoses/lines.

On heater core leakage look for coolant on the bottom of heater core housing and for windshield fog up and also a sweet smell from heater is a good indication of a leak.

Let us know how the vacuum test/check goes.
There is also a recalibrating procedure on it.
With ign off pull RDO/BATT fuse for a minute and put it back in and turn ign on and it should go threw the recalibrate procedure.

I have somewhat the same problem on my '99 burb.
You can just barely get it warm when freezing outside.
In addition it blows hot air to the passenger's foot side but cold on the driver's side.

I also noticed that the aircopump is activated when the control is turned to windshield/feet. You can even feel a slight "klick" inside the switch when turned right beyond that position (contact?)
Is this normal? Even when the temp. control is set to max heat...

I will try the recalibrate procedure MT-2500 suggested first.
A few months ago the battery went dead, maybe that caused the problem?

I have never had any problems with the heat in my 99 blazer but i have a friend who has a 1997 jimmy and had a ton of heating problems this winter. he kept changing his thermostat but the problem would only be temporarily fixed. he finally changed his intake manifold gasket and now the heat is fixed. it's an expensive job but it worked. i'm not sure how much he paid, i think it was somewhere between $200-$300.