Vacuum leak in dash controls and the engine is working to hard to hold the heat control shut.
daytime running light module under drivers side dash
Under the dash. Supposed to be. It could be under the hood.
Bad brake light switch, it's on top of the brake pedal under the dash.
under the driver side dash
possible rollover senser under dash!
under the dash behind the glove compartment. the entire dash needs to come out to remove it
No Relay, Just A fuse located on the drivers side dash when you open the door. It is under DLR (Day time running lights) silver finned box under dash, right side of sterring column
check fuses under dash drivers side and under hood drivers side
Be sure the battery connections are clean and tight.
Does air come out at defrost vents? Defrost is the default position. Check for a vacuum leak either under the hood or under the dash Check the operation of the vacuum actuated motors under the dash Check the operation of the selector switch
bad heater core under dash
I believe it is under the dash on the pass side of van. If your daytime lights go on and off when driving it you better get it change >mine went out the security light came on and would not start.