I had a 96 Bonne SE intermittent heater/ac blower motor and purchased new one for $46, started replacement of my new motor and fan. However, when I took the bad unit out the plastic motor cover (part number 52-468-407) fell apart into about 5 pieces. Here'* the weird thing--several other Bonne firewalls I've seen have the blower motors without a cover..? Is it even necessary to replace the cover or should I just press on without it? I looked the part number up on some GM Parts web sites and ... nothing!