We have a 1997 Chevy Suburban. During the winter we were in Utah and our front blower motor started shrieking like a banshee, so we replaced it (it was very, very cold outside so not blowing hot was a problem. Also it was a cold job replacing it).

However, after we replaced it it seems as though the fan has two speeds: High, and off. Specifically it doesn't matter where on the dial we turn it, if it's not at high it's not blowing.

Why would it be doing that, and how can I fix it? The motor that I bought is a "premium quality blower motor" by Murray climate control. Model PM149, I think?