Heater Blower works intermitently

I need some help.I have a 1990 Pontiac Bonneville SSE With all the electronic stuff.The question i have is what would make the heater turn on and off when it feels like it.I will start the car one time it will work for a while then the next time it will not work at all....If someone could help it would make my day... :) Thanks

I had a similar problem on my '96 Bonny.
The blower motor would come on or go off or work slower than it should. I originally thought it was an electronic control problem because of the failure mode but I was urged to check the blower more thoroughly. When I removed the old blower, I jumpered power directly to it and it worked fine until I moved it around, then it stopped until I jiggled it again. I replaced it and the new one works perfectly.

I am having the same problem with my heater on my 95 Bonneville. Haven't had a chance to replace the fan. What I do when the fan is not working, I raise the hood and tap the motor with a stick and the fan comes on. real Hi-tech. the motor goes for about $ 55.00. I am waiting until warmer weather to replace the fan. The fan motor seems to work when the temp is 45 degress or above.

Thanks alot it was the blower motor.I picked it up from AutoZone for $28.99 Thanks for all the help

Thanks alot it was the blower motor.I picked it up from AutoZone for $28.99 Thanks for all the help

- did you replace the motor from underneath the hood on the firewall ? I need to replace mine too, but thought I would have to take the dash off. Does it remove and install easily ? thanks.

The blower motor is removed/installed from under the hood at the firewall. There's one electrical connector and about 5-6 small screws. Sometimes it takes a little fussing to get it out from between the blower box and valve cover but it does come out without removing any other parts.

I had same 96 Bonne SE intermittent heater/ac blower motor problem 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's the weird thing--several pix I have seen in AF of Bonne firewalls show 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!

Update -- Used the old rubber gasket and got thicker washers so I could use the old screws. Worked great so far!!