Block heater-- my dodge has a block heater, I plug my cord in and the next morning when I start the start lights (swiggly line) does not come on and the truck starts easily. Should my cab heat begin blowing warm air immediately?

 

The start light (wigly line) is your glow plugs. How long that stays on is directly related to the temp. of your engine. If you notice it will not stay on long if you start your truck after you shut it off for a short time.

My truck blows very luke warm air soon after start up if its pluged in. Not hot air like when its runnig, but warmer than when not pluged in.

 

Cummins dont have glow plugs. They have an intake grid heater. Heats the air entering the engine right before it goes into the intake. The WTS (wait to start) light doesnt come on because some heat from the truck being plugged in has made its way to the temp sensor and has basically told the computer your truck is warm.

Block heater warms the coolant in the block. Since the grid heater is attached to the intake, which is attached to the head, which has coolant in it, obviously some of that heat will permeate into the intake. Its all good...

 

The WTS (wait to start) light doesnt come on because some heat from the truck being plugged in has made its way to the temp sensor and has basically told the computer your truck is warm.

Without the block heater plugged in the WTS light stays on for a few seconds before I start so how does the sensor sense warmth before the engine even is started to allow it to go off?

 

The grid heater warms the intake and that's how it knows it's warm.