Low amount of heat from upper vents

Ok, I searched (maybe not carefully enough) and couldn't find anything like this here. I have heat no question, but even on full blast it only trickles from the upper vents. Now, on the other hand turn on the A/C and it pours out. I can hear the vents moving and the blower is blowing, naturally. I'm guesssing the heater core is ok, 'cause I have heat. Any ideas?:banghead: BTW, the car is the 99 Lumina 9c3 police package.

I can tell you that certain model cars are designed to "damper" the heat when air is asked for at the vents- Most designers avoid putting full heat in people's faces- to avoid that complaint-- likewise the systems are designed not to put full a/c cold on the defrost (windshield)- I know for a fact the later model U-vans have damper doors to restrict the flow of heat out the vents when on full hot- the actuators actually throw a secondary door to restrict the air flow out the vents when in full hot mode--I have had folks complain about this- and there is a TSB on it in the U-vans (Montanna, Silhouette, Venture) to disable the secondary door- if they complain. It is pretty simple- most folks want heat at their feet, and cool air in their faces- not heat in their faces. I once worked on a ladies car who wanted full a/c cold air to come out the defrost- but there was a whistling noise-turned out to be the secondary air dampner door at the defrost- You can look at your actuators and see if your vehicle has a secondary door- It will have two arms on it- and the TSB said to simply disconnect one of the arms....

I can tell you that certain model cars are designed to "damper" the heat when air is asked for at the vents- Most designers avoid putting full heat in people's faces- to avoid that complaint-- likewise the systems are designed not to put full a/c cold on the defrost (windshield)- I know for a fact the later model U-vans have damper doors to restrict the flow of heat out the vents when on full hot- the actuators actually throw a secondary door to restrict the air flow out the vents when in full hot mode--I have had folks complain about this- and there is a TSB on it in the U-vans (Montanna, Silhouette, Venture) to disable the secondary door- if they complain. It is pretty simple- most folks want heat at their feet, and cool air in their faces- not heat in their faces. I once worked on a ladies car who wanted full a/c cold air to come out the defrost- but there was a whistling noise-turned out to be the secondary air dampner door at the defrost- You can look at your actuators and see if your vehicle has a secondary door- It will have two arms on it- and the TSB said to simply disconnect one of the arms....

The mystery whistling noise! I hear like a whistling when the face vents are on, but I hear that noise while the a/c is on too, but the a/c pours forth like no tommorow. The noise is on and off, no vacum leaks detected.

Feel both heater hoses and make sure they are hot. A partially plugged heater core will cause this problem. If one hose is a lot hotter than the other one this is your problem. Otherwise check for a broken blend door a common problem on some vehicles.

Generally, that is correct. However, there will be a noticeable difference in the temperature of the coolant hoses for an idling engine when ambient temperatures are lower and the heater blower is moving a relatively large volume of air.

Mornings here have been between 5-10ºF in the past several days, and if the weather in the Bronx is similar, a difference in hose temperatures should be expected unless the blower is off or the engine RPM is well above idle.

check vacuum line going to vac resivoir. (it may be by the battery) if vac line has hole or is broken the air flow will come out vent/ac ducts cause n ot enough vacuum is reaching switches to move doors to direct air flow to defrost ducts. had same problem on corsica & lumina