My blower will not go on the highest setting so I can't get maximum heat. Every thing else works but that setting. Any suggestions?

 

More details needed before I can help you with this. These vans are pretty much all wired the same but sometimes the options make a difference.

What is the year, model, trim package, and does it have an auto mode?

 

I have a 2005 dodge grand caravan. I have automatic controls and no options for rear

 

Was the van converted/modified and the rear options deleted? I’m only finding wiring diagrams that include rear controls as well. In theory it shouldn’t matter but I was just curious.

There’s a few possibilities for what’s causing the problem. Instead of being controlled by a typical resistor, the blower speed is controlled by a solid state resistor (blower control module as Dodge calls it) with the speed selection just being an input from the HVAC module. First you need to narrow down what’s happening when high is selected.

Start by unplugging the blower motor. Hook up a test light in place of the blower. With the key on, cycle the speed control through its different positions. If you start at off/low and work your way up, the test light should steadily get brighter. When you select high, does the light go off?