The following is the procedure for replacing the HVAC blower motor in a 1974-1978 Chrysler full sized car. Some of these steps are also required to replace the power antenna. The same steps are to be followed if the car has the ATC or the non-ATC HVAC system.
Skill level: Advanced/professional
Special tools & materials recommended:
15' cargo strap, with rubber-coated hooks
6' cargo strap
antenna nut spanner
12-14 ga. Electrical splices and splicing tool
Squirrel cage fan wheel
Turn the steering wheel all of the way to the right. Fully lower the power antenna.
Have a helper lift up the right front corner of the hood. Unhook the hood spring from the bracket. The hood will need to be held up so that the end of the spring is above the bracket. A stick is not recommended. I hook a cargo strap inside the trunk and to the front of the hood, in a place where it can't slip. (see my engine replacement pictures). If outside, a 6' cargo strap should be hooked to hold the hood down, so that there is tension on both straps. This keeps the wind from blowing the hood loose from the strap that is holding it up.
Remove the metal bracket that holds the hood hinge ramp. There are three bolts going into the top of the fender, and two nuts going into the firewall.
Now you have access to the blower motor. Remove the three nuts and the special washers holding the motor in, and the rubber blast tube.
Take as many bolts as necessary out of the fenderwelt (Chrysler calls it a splash shield) as is necessary for clearance to do the next steps.
Remove the power antenna. There is a nut at the top, and a single bolt in the bracket at the bottom. It may be easier to slide out after you accomplish the next step.
There is a metal bracket that runs from the fender to the bottom of the firewall. Remove the top two bolts, which go up into the fender from underneath. Remove the lower bolt which goes from left to right. If you don't see it, the head may be covered with body glaze. There is one more bolt at the bottom, going into the firewall. Loosen this bolt, but you don't need to remove it.
Slide the blower motor out. The fan wheel is almost impossible to remove in one piece, which is why a new one is recommended.
Remove the rubber gasket from the blower motor base. Clean it, and secure it to the new blower motor with a few dabs of weatherstrip adhesive. Use just enough to keep it from sliding around, so that you can still remove the gasket and reuse it later. Put the blast tube into the motor.
Install the new fan wheel and the clamp that holds it on.
Feel around and clear any debris out of the blower case, and slide the new motor into place. It can only go in one way.
Reinstall the special washers with the conical side inward. This centers the motor. Install the nuts. Slide the blast tube onto the nipple.
The power antenna may be a pain to get back in. The special washer on top of the fender will only go in if you have the antenna rotated to the correct position. There is also a star lockwasher on the antenna shaft which must be rotated to the correct position, where one of the star points has been pushed in so that the washer's tab can go in.
Cut the connector from the old blower motor and splice it onto the new one. Observe the correct polarity...black goes to black.
Reinstall the brackets, let the hood down, and put the bolts back into the splash shield.