GMC Repair: heater, heater hose line, radiater

Question
i have a 92 gmc full size truck and the heater is warm but even on high the cab is not very warm . we put in a new thermostat ,theres preston in the radiater and  I dont know why it wont get warm enough to be on low or even med.

Answer
Hello nancy

This could be a bad valve in the heater hose line if yours as one some did some did not .
If it does open it up maybe stuck.

If not then have the heater core checked could be pluged.

Good luck to u hun and u have a pretty name pete