Stearn, check the link that Ding-a-ling gave you. It is my saga of fixing my dash air. Hopefully it will be of assistance to you. There is another link you will find there to pictures of how mine was set up. Hope this helps you find the problem.
Tom and Barb
'07 Winnebago Voyage 35L
Workhorse W22 chassis FMCA 219315
That is caused by the resistor failing. It is located under the hood on the heater/AC housing. It has a 4 pin connector and is held in place by 2 screws and sealed with silicone. Replace the resistor, and all will be fine.