PD150 Oil cooler & Frost Heater

I've had a frost heater for 3 years on the car, works like a charm. I upgraded to the PD150 oil cooler and now the frost heater doesn't warm the engine. Has anyone else had this problem with this combo? The heater is warming the coolant line.

The PD150 oil cooler has the in and out pointed up vertically (stock ones are horizontal), so i don't think the heated fluid is going down into the cooler, then up to the rest of the engine?

i used a frost heater + pd150 oil cooler in two of my cars and worked fine. i've since removed the frost heater, and i can't remember exactly how i plumbed it, but i never had an issue with it not heating the engine.. pretty sure you want the outlet of the frost heater going up to the upper radiator hose. the return comes from the oil cooler, iirc.