QuestionHeadlights pop up but will not turn on. However, they will work on occasion. Sun-roof won't retract most of the time. Electric windows will not open/close on occasion.
Any ideas?
Tom Nelson
AnswerHi Tom,
I'm going to suggest we deal with these problems in two steps. The first will be the grounding problem and the second will be the relay/control problem (which can get a bit complex).
So, let's first start with the headlights (of the three they are the simplest).
Find the three wires powering up the left headlight (should be yellow, white and brown). Note: these wire colors I'm mentioning are for a '84 944, which is the only wiring diagram available to me...but they should be the same as the 928...but if not... you're looking for the two colored wires that end at the plug-in for the headlight prongs. The third wire, which will be brown (ground) will be right there too.
There are two steps to take at each headlight:
1. Trace the brown wire so you can see both ends. Remove each end, one at a time, and clean the terminal end and its mounting surface so the corrosion, dirt, crud, and/or rust is completely gone... and the connection can be reattached in all its gleaming glory. At the other end, you will likely find a "glob" of brown wires (glob is the technical term for a wad of wires resembling tangled spaghetti). Clean your headlight ground wires, and while you're there it would be wise to renew all those brown wire connections and their mating surfaces. Globs of wires just love to be clean and their terminal ends love to be gleaming.
Get out your multimeter...what you'll be checking for here is continuity. So here's the test: put one probe end of your mutlimeter on the negative (ground) terminal of the battery and the other probe end in the newly refreshed ends of the brown wires...one end at a time. In each case the multimeter should "buzz" or even better: give you a .000 readng. A good multimeter will start with a 1.000 reading with the probes not touching anything, and will go to .000 when the probes touch each other or you have perfect continuity through a wire...which is your goal.
2. Turn on the headlights and by now the left headlight will be shining brightly. Right? No? OK, so the ground may not have been the problem. If not, set the multimeter to 0-20 DC volts, so you can test to see if the headlights are receiving 12 volts when they should be. Touch one probe end to the connecting point of the yellow wire and its headlight prong and touch the other probe end to a good gound. How fortunate for you, the brown wire glob is a very good ground now that you've cleaned it it and reattached it, so it's a perfect place for your probe end. The reading should be 12 volts (or actually very near the reading when you measure across the two battery terminals themselves. Battery voltage should be about 12.8.) If you don't get voltage, or very little voltage check the connection of the white wire at the other headlight prong. The reason you have both the white and the yellow wires at the headlight is to powerup the headlight itself, or the high beam, depending on the position of the high beam selector. For this test one oof the colored wires should have 12 volts.
That's enough for one session. I'd appreciate it if you could write back to me when you've completed these steps, Use the follow-up question feature of All-experts. Please let me know what results you had. What's working, what's not...what each test revealed, etc. Then, if you're willing, we can tackle the sunroof.
Looking forward to hearing your headlight success story....,,,,,,
Dave
