Review on Zerostart 3308003 Circulation Diameter Approved by Patrick Reid

I installed this on my 2009 Isuzu NRR Rollback and am reasonably happy. It is simply installed in the heating hose line. However, I only gave it 3 stars because it doesn't work too well on the coldest days. It circulates a small amount of water and keeps the engine warm, but usually not enough to move the temp gauge. This creates a slight build-up of heat in the cab, but this is slowly dissipated when the truck is in operation. I think it's better than no water heater/circulator at all.