Yeah, trainers suck.
It has been raining torentially here with temps right above freezing so I have been doing some HR based workouts on the trainer like 2x20's.
Its a motivation issue though. I hate being on the trainer so Ill try to ride up to my zone with percieved exertion and then look down at the low HR number and be like are you kidding me?
Just stick with it man and HTFU.
I suggest planning on using the first 20 min to ease into it physically+mentally and to make any adjustments on the resistance 1/4 turn at a time.