I put on a Kats Radiator Hose heater, really does a nice job, simple and I have warm air much more quickly in the cab. However now my Grid Heater does not come on and I think it should when it is 10 degrees, misfires a few times when first started. If I don't plug in the Coolant heater the Grid Heater comes on, no misfires. In my diesel truck I am installing a manual push button for the glow plugs but looking at the wiring diagram the Roxor seems far more complex and I don't want to mess with the ECU. Guess the Diesel Freaks tune will do the job I am looking for. Good Info, thanks.