Oldsmobile/Buick Repair: 1996 Buick Roadmaster..poor heating, buick roadmaster wagon, 1996 buick roadmaster

Question
-------------------------Upon further investigation, I note that the heater works well when the blower/fan speed as set at low. If blower/fan speed is increased the air blows cooler. Both heater hoses are warm at driving temp, but upper is warmer than lower. If blend door is the problem, how do you adjust it? Thanks!!!
Followup To
Question -
The heater in my 96 Buick Roadmaster wagon with GM LT-1 engine blows cold...or lukewarm at best. Heating improves at highway speeds, but not much.
Thermostat? Heater core? Blend door? If its a heater core or blend door can I/should I try to repair it myself? Many thanks!
Answer -
hi bob yes if blend door and it probably is you should be able to adjust it .heater core a little more complicated.but if both heater hoses are hot at norm operateing temp has to be controls for heat distribution ty billymac please rate my help

Answer
hi again bob.if blend door is the prob here is what you do start eng get under dash bye heater box move the temp selector from hot to cold watch what happens you will see a door opening and closeing put selector back on hot wait for door to stop now push rod so as to open or shut door the same way the motor is trying to .you will hear a ratcheting noise this is normal this is the only adjustment..but getting back to those heater hoses they should both be 185 degrees when eng is norm.at 185 you can touch the hoses but you will not be able to comfortably hold your hand on them.if one is cooler then the other core is bad .please take a min to rate my help ty billymac