Electrical devices not working properly

86 911 · 86 911's Garage

Here is the main problem I've been having:
I was out driving yesterday, parked the car in a parking lot, came back to start it up, and it wouldn't start. I checked the battery and found that the Power cable had come loose and was off. I put the cable back on, drove home slowly, and and tightened the power cable up (note: I did not take the Ground cable off at all). After the Power cable was on tight, the car started fine, but I have to wait about 2-5 minutes before these devices come on:
1) CD Player/Radio
2) Headlights (parking lights come on instantly)
3) Radar Detector (plugged into cigarette plug)
4) Instrument panel lights will not come on at all*

*blinkers will work, warning lights work, but only the lights in the instruments won't work.

Also, the battery is about a year old, and the alternator was tested about a year ago and is in great shape. All fuses look good. The car is a 1976 911 with completely redone wiring (wiring diagrams probably won't help). What could be causing this problem?

Thanks.

911pcars · 01-07-2006, 02:31 PM

Running the engine w/o the battery cable connected can spell doom for the alternator. Check the battery voltage with a voltmeter with the engine running, then let us know.

Not sure why the accessories are working on a delay basis. It's probably related to the above.

Sherwood

86 911 · 86 911's Garage

Okay, here are the results:
Without the car running: 14-15 volts
With the car running: 17 volts.

When the car is started, there is no drawback in voltage.

I should add that everything works fine with the key turned to the position before "start", but when the car is finally started, the above devices mentioned do not work until later.

svandamme · svandamme's Garage

14-15 volts engine not running is impressive
17 volts engine running is just as impressive

if anything , both values would usually be 12 volts or less for non running
and maybe 13 volts for running , and even that would be optimistic

it's a 12 volts system .... 17 is waaaaaay out there

syncroid · 01-07-2006, 03:51 PM

Your alternator has said good bye. Normal running voltage is between 13.25 - 14.25 volts. The static (non-running voltage should not be more then about 12.5 volts.

86 911 · 86 911's Garage

That's interesting. The car has been running off of 14-17 volts since I got the car a year ago. As I recall, I don't think it's a 911 alternator, but I could be wrong. Here is what more diagnosing shows:

If the key is in the "run" position (the position closest to the starting position) everything will turn on, but sometimes intermittantly turn off and then on again.

Could a loose wire be causing this?

rotorhead · 01-07-2006, 04:26 PM

Sounds like your Voltage Regulator is bad. It is only a $20 part. If the VR goes then the voltage output of the alternator increases, this can lead to strange electrical problems.

911pcars · 01-07-2006, 04:57 PM

Nominal storage battery voltage at rest (no load) should be in the area of 12-13 volts. Are you sure your voltmeter is accurate?

Nominal charge voltage while engine is running is around 14 volts.

Assuming the voltmeter is reading +3 volts high, the system seems normal. If the voltmeter is accurate, the charging system is allowing the alternator to create too much voltage. Have it checked out.

As to your second issue; delayed activation of accessories - got me. I'd like to know what's going on too. Sorry I can't offer any help here.

Sherwood

AtomicDog · 01-07-2006, 05:10 PM

86 911,

syncroid is correct.

I was chasing down some strange behavior on my '86 and noted 12.4 volts with the car off, and over 15 volts with the car idling. I think the Bentley manual lists 14.6 volts as the high end of the band with the car at 2000 rpm. Needless to say, I didn't even bother going to 2K with an idle voltage of 15.6.

When I took my alternator to a well respected electrical shop, they informed me that the alternator could not be economically rebuilt, as the stator was toast.

How are your fuses and bulbs?

Pray that your fan shroud is in good condition when you do the alternator replacement. Mine was well cracked in several locations... The repair is still in progress, and I'm doing some "improvements" on the replacement shroud to improve the airflow - hours of Dremel work. I hope to have some pictures when I'm done.

Good luck.

Chris

86 911 · 86 911's Garage

The fuses and the bulbs look good. Is the voltage regulator the half cigarette box shaped thing on the back inner panel of the engine bay?

AtomicDog · 01-07-2006, 08:25 PM

Nope, internal regulator. It's the large black wart that requires the cutout on the air deflector on the back of the alternator.

Chris

86 911 · 86 911's Garage

I got the job done. It was only that the wires going out of the ignition switch near the steering column were fried together and shorting out. I put some insulator tape around a few of the wires and they are great now. I also got a chance to fix and solder some other loose connections under the light switch. It was a mess down there. The P.O. only twisted the wires together to act as a "connection". lol.