When it comes to climbers, you never prune them until AFTER their first flush of blooms in the spring. Then you remove ONLY the dead or diseased wood. The reason is that the blooms for the next season will come from the wood created this year. If you prune it now, you will be removing the canes that it will bloom on next year, and I doubt you want that. If, in the fall, the plant gets "leggy," that is throws lots of long scraggly canes, you may cut it back 1/3 to make it more manageable, BUT don't prune it as such. Wait until after that first flush in the spring.

Roseman
Your advice is mainly for once blooming climbers that bloom on year old wood. Modern climbers, Autumn Sunset included, bloom on new wood. Modern climbers I had to severely prune this year have bloomed well on new wood.

Having said all that, I agree that pruning climbers should not be done until after the first bloom, except for obviously dead or damaged canes.
The best bloom is usually the first one and the more canes kept on the bush, the more blooms. After the first bloom new growth will provide additional canes for more blooms.
Regarding removing old non-productive canes. I watch for signs of decreased flower production and old looking bark on a cane. When this occurs, I cut the cane back to promote new growth from the base. An older non-productive bush can often be rejuvinated by removing 1/3 of the biggest canes each year for three years. After that, keep an eye on it and remove only those not producing many flowers.
Normally, in cold growing zones winter dieback will take care of this problem except on the hardiest roses. If a cane is removed after the first bloom, it gives the new growth all season to harden off before winter. Done now any new growth may be killed this winter.
Depending on where you live in Washington, your winters can vary from severe to moderate. Except for making a climber manageable, do your pruning in the spring after it blooms.

The advice to remove some of the old canes is generally applicable to climbers 5 or more years old.

Thank you all for your great advice! I never thought I'd be so attached to a plant, but I really love these Autumn Sunsets. They climb a trellis that frame the entrance to our front porch. If you're interested, I have pictures on our website. (I'm not sure how to post pictures here)

www.genericnewsletter.citymaker.com

Go to "Family Blog" and "Entry Garden Done" (last 2 photos) and a few entries later, "Abby's Doll Party" (1st picture show the rose in full bloom behind the partygoers!)

Thank you, Eileen

I had that one on a trellis until I recently moved and I never did anything but deadhead it.
It got to be a monster but I love the cottage garden look so it was just perfect.
Just my opinion, but I wouldn't prune it down to 4 feet.
I love that Rose and I can't wait to grow it again.
I'm starting over and that one will be in the ground next Spring.
Chuck