Q — The AC blower motor on my 1980 Carrera has been working very erratic lately. It will work one time when I drive but when I stop the car to go shopping for a while, I come back and it won’t work. If I let it sit for a few days it will work then and then not work. It even went out for a few minutes then came back on while driving. What is your opinion on the problem??? Motor going??? Control Switch?? Ground??? So just where is the motor located??? I assume it is in (what is commonly called) the smugglers box. I have a part # of 901 624 901 00 for the motor. Is this correct??? What is the cost of new motor??? Thanks Gary
A — Intermittent problems are the most challenging and all too often, do-it-yourselfers fire the “parts cannon” in desperation. Don’t do that yet. There are some things you can check and even if they do not cure the problem, consider routine maintenance instead.
First check the fuses, but not to see if one is blown, that would be far too easy and the blower wouldn’t work at all. With a strong light, notice the appearance of discoloration on the fuses and the wiring at the fuse block. Notice the different color of the fuses (which corresponds to their load value) and make yourself a diagram with those colors noted. If you find that some of the fuses have shrunk, you have fallen victim to plastic, third world fuses. The original fuses were ceramic and they do no melt or shrink. F.Y.I. Yellow is 5 amp, white is 8 amp, red is 16 amp, and blue is 25 amp.
Next, disconnect the negative battery cable and inspect the fuse box for integrity of the plastic base and then check all the screws securing the wires to the fuse holders. To check the screws, hold the base of the wire holder with needle nose pliers as you try to loosen then retighten the screws. If power flows through an overheated circuit, the screw might seem tight but be partly seized in place due to the heat generated. Typically, I find some screws loose, most of them tight and occasionally, a heat damaged terminal or fuse box. On many older cars, an auxiliary fuse box contains the AC fuses and I have found these broken.
While you are working on the fuse box, mark then remove the relays and look for melted sockets. These sockets can be purchased from Porsche and although not a simple job, they can be replaced. At a minimum, I suggest that you clean the sockets and fuse box with electrical contact cleaner while protecting the surrounding area. After cleaning, a light coating of Dielectric grease (non conductive) is useful for corrosion protection.
At the battery, there are a number of positive wires and grounds that should be inspected and tidied up. The grounds also warrant a good look. And finally, don’t forget connections under the dash and in the center console where the controls reside. The AC system draws a lot of power and every place where a main wire plugs into a component should be felt and if needed, tested for voltage drop between the battery and that point in the circuit. –MC