How To Fix a Frozen 740 (1985) Heater Fan Motor


This installment will cover the situation of water seeping into the fan blower motor and freezing the motor shaft, causing the #16 fuse to blow. This happened to my 1985 740 a few weeks ago (March) after I drove the car through a brushless car wash. The next morning the fan didn't work and fuse #16 blew every time I replaced it. I figured there was a good chance that water had entered the motor and froze. After 3 days it wouldn't thaw, even after a 20 minute drives to and from work and after standing all day at -10 degrees Celcius. The same steps can be followed if you must replace the fan motor. (NOTE: This procedure applies to pre-1990 740s and may not apply to newer models)

  • 1. Remove the plastic caps covering the 2 front screws that hold the interior plastic trim strip to the floor. Lift the trim slightly and slide the injector computer panel cover towards you. If it's cold, be careful you don't crack the brittle plastic.

  • 2. Remove the black plastic tray under the glove compartment by sliding it towards you. Slide the Jetronic computer off it's guides, exposing the metal rail. There is no need to disconnect the computer. Unscrew the 3 retaining screws and remove the rail.

  • 3. Peel back the carpet and underpad, exposing the vertical fan blower motor. You will see the attaching screws, the power lead (purple), a ground wire and the hot air hose.

  • 4. The blower fan and squirrel cage assembly unit will now drop into your hands. At this point, I realized that water had accumulated around the motor shaft, preventing it from rotating and causing the #16 fuse to blow. This image shows the heater tube hole and the rusty crud that was trapped inside. Please click here (24K bytes).

  • 5. I had replaced the original Volvo (AC Delco) fan assembly 18 months ago and still had the other fan for comparison. It was now that I realized the replacement fan motor didn't have drainage holes drilled into the bottom fan cover, even though the replacement was AC Delco.

  • 6. After drying the interior and applying power to ensure that there was no permanent damage, I drilled the 2 holes in the bottom cover and an additional hole since my car is parked on an incline. This will allow even rainwater to now properly drain. I sprayed rust proofing paint on the motor cover and prepared to reinstall the motor. To view a picture click here (29K bytes).

  • 7. I applied some silicon sealer to the mating surface and attached the heater tube. Assemble the motor, rails, Jetronic computer and plastic covers in reverse order.

  • 8. Except for the time spent correcting the deficiencies, this job cost no money at all. Even if you must replace the fan motor, you will clearly save 2/3rds of the cost of having the job done by your garage.