Alternator idiot light is on
04-23-2019, 07:20 PM
#16
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04-24-2019, 09:08 AM
#17
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Join Date: Dec 2009
Location: Lancashire, England
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Had the same problem, battery light on, would sometimes go dim at higher revs....
Took alternator out and had it tested, the rectifier was diagnosed as the issue and replaced, re-installed it and now working perfectly.
See below
http://911uk.com/viewtopic.php?t=133...14c731511b5337
Trev
Took alternator out and had it tested, the rectifier was diagnosed as the issue and replaced, re-installed it and now working perfectly.
See below
http://911uk.com/viewtopic.php?t=133...14c731511b5337
Trev
04-24-2019, 01:17 PM
#18
Burning Brakes
I have that dash voltmeter and it's terrific.
I added the unit below which allows power to other gadgets- phone charger, Valentine, etc.
A bit cumbersome, but functional, cheap, well made.
I added the unit below which allows power to other gadgets- phone charger, Valentine, etc.
A bit cumbersome, but functional, cheap, well made.
04-24-2019, 03:58 PM
#19
Nordschleife Master
Another Rennlister had a bunch of the little plastic housings, and gave them out a few years ago. got the voltmeter off Amazon. all in all, a pretty simple DIY. maybe a 3 on the 1-0 scale.
04-24-2019, 05:05 PM
#20
7th Gear
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Update to idiot light
Well, all the suggested easy fixes have not resolved the issue of the light. So I have removed the alternator again (not so ugh, found short cuts and was efficient) and had the rectifier checked and was all good. Will re-install and see what happens. When I spoke to the alternator rebuilder, he had me test the blue wire for continuity to the block in the engine and it tested fine. Also, had me connect a voltmeter to the blue wire and then turn the key to on (wrapped the battery/power wire) and had only .5-.7V. He felt it should be in the 2-3V range. Also, if I were to ground the blue wire with the key on, the "idiot" light should come on which it did not. So, back to square one if the light stays on after re-installing I'll keep you all posted and thanks for your help.
04-24-2019, 07:20 PM
#21
Rennlist Member
I guess you want to know if the alternator has failed to charge. If I was down just below 14.0V under the same conditions, then I have a problem like a bad diode in the rectifier pack.
This voltmeter install started back in 2003 when I installed one on my motorcycle.
05-27-2021, 12:17 AM
#22
Rennlist Member
If your car reads between 13.5 and 14.2 volts with the engine running and between 12.5 and 12.8 a few seconds after you turn it off your alternator is most likely working correctly and is most likely wired correctly.
I looked at the wiring diagrams and the wire from the battery light in the dash clock is a shared circuit that goes to the alternator, alarm, abs & central informer controllers so it is not a simple system.
This leads me to the idea of simply disconnecting and reconnecting the battery as it may reboot/reset some internal software switch in one of the controllers related to this circuit.
An idea I had was that the alternator diodes are part of what is called a rectifier bridge circuit where sets of diodes are set up like one-way valves to redirect the alternating current from the alternator rotations to direct current. For example, something called a full wave bridge design using more diodes produces a smoother level of DC current, a half wave bridge design produces what looks like pulsed DC current. Conceivably if one or two of the diodes in the rectifier circuit internal to the alternator are bad creating a pulsed DC condition this may be causing the warning light controller to turn the light on. From the wiring diagram, the alternator has multiple diodes in it that suggest it is designed to produce very quiet electrical power. The good thing is that this condition can be check without removing the alternator as it presents as a noise in the alternator circuit. Any qualified technician should be able to tell you if this theory applies to your car.
A very very long shot is that the solder joints in the clock are known issues in our cars and to pop out the clock and reheat the internal solder joints on the board is relatively easy, I did it at the kitchen table years ago and seem to recall the solder joints to the clock motor need to be released to get the board out. Then make sure the bulb connections are good.
Some folks replace the some of the dash display lights with LED bulbs. These are not resistive loads like the original bulbs and also act as one-way electrical valves, this may be part of the issue if you have replaced any of your display bulbs.
Finally, do you know why the alternator failed in the first place as this root cause may still be present? Have you had any servicing done recently, just before the alternator issue cropped up?
Hope this all sorts out. The upside is you can still drive your car.
Andy
I looked at the wiring diagrams and the wire from the battery light in the dash clock is a shared circuit that goes to the alternator, alarm, abs & central informer controllers so it is not a simple system.
This leads me to the idea of simply disconnecting and reconnecting the battery as it may reboot/reset some internal software switch in one of the controllers related to this circuit.
An idea I had was that the alternator diodes are part of what is called a rectifier bridge circuit where sets of diodes are set up like one-way valves to redirect the alternating current from the alternator rotations to direct current. For example, something called a full wave bridge design using more diodes produces a smoother level of DC current, a half wave bridge design produces what looks like pulsed DC current. Conceivably if one or two of the diodes in the rectifier circuit internal to the alternator are bad creating a pulsed DC condition this may be causing the warning light controller to turn the light on. From the wiring diagram, the alternator has multiple diodes in it that suggest it is designed to produce very quiet electrical power. The good thing is that this condition can be check without removing the alternator as it presents as a noise in the alternator circuit. Any qualified technician should be able to tell you if this theory applies to your car.
A very very long shot is that the solder joints in the clock are known issues in our cars and to pop out the clock and reheat the internal solder joints on the board is relatively easy, I did it at the kitchen table years ago and seem to recall the solder joints to the clock motor need to be released to get the board out. Then make sure the bulb connections are good.
Some folks replace the some of the dash display lights with LED bulbs. These are not resistive loads like the original bulbs and also act as one-way electrical valves, this may be part of the issue if you have replaced any of your display bulbs.
Finally, do you know why the alternator failed in the first place as this root cause may still be present? Have you had any servicing done recently, just before the alternator issue cropped up?
Hope this all sorts out. The upside is you can still drive your car.
Andy
https://rennlist.com/forums/993-foru...itic-draw.html
I'm noticing a wining noise from the engine bay. Thought maybe I just never noticed it before and that it was normal but now thinking maybe could be a blown alternator diode?
05-27-2021, 10:14 AM
#23
Rennlist Member
By the way, a three-phase alternators have 6 power diodes.
