Only have heat when engine accelerates, flushed heatercore, water is running . on 1996 Dodge Ram Van 1500

Flushed heatercore, changed control valve, water is flowing thru heatercore very clean , no sign of coolant thou.

Had new radiator installed last yr. due to a leak when i opened the rad cap. i didn`t see coolant there should be visable coolant at the top right?
Heater hose is hot the other not as equally hot.
Please help!

Asked by for the 1996 Dodge Ram Van 1500
I took a 1999 heater vent apart last week and there are put together in pieces and each connected piece has a seal.. the seal was rotted away in most places so you can buy seals for it or do it yourself and use caulk or pieces of reinforced rubber pieces to seal those spaces where the air is escaping.. just for the record.. i used clear metal roofing caulk to seal it but had to leave it sit for 10 to 12 hours so the caulking would dry...