Alternator not energizing until engine revved.
03-12-2013, 01:34 AM
#16
The alternator warning should be illuminated with the key in the on position and extinguish when the engine is running if the alternator is working. On the early 944 the alternator warning lamp is connected to the alternator field excitation circuit. If the lamp burns out the the. Alternator will not function correctly.
03-12-2013, 09:42 AM
#17
Team Owner
Yep, as I said above that bulb needs 12v on BOTH sides to go off. An LED in there, which is basically a diode that allows voltage to flow one way only, would really mess things up.
For those not to familiar with electronics, you need a voltage difference for a light to come on. Normally we are used to dealing with a difference of 12v on one side of a bulb and ground (0v) on the other. But on charging circuits it is common to have the battery 12v on one side of a warning bulb and the alternator 12v on the other. That is why when the engine (alternator output) is not running the light comes on and goes off as soon as you start the engine. Hope that makes some sense to someone.
For those not to familiar with electronics, you need a voltage difference for a light to come on. Normally we are used to dealing with a difference of 12v on one side of a bulb and ground (0v) on the other. But on charging circuits it is common to have the battery 12v on one side of a warning bulb and the alternator 12v on the other. That is why when the engine (alternator output) is not running the light comes on and goes off as soon as you start the engine. Hope that makes some sense to someone.
03-12-2013, 12:58 PM
#18
Nordschleife Master
actually you do need i diode with your bulb, or use an led. , thast why an led is often used for this. if the alternator voltage is above battery voltage you dont want to forward bias the diode, but if the alternator voltage dropes below battery voltage you want to forward bias the led getting it to light and indicating alternator failure.
05-03-2013, 10:59 PM
#19
Drifting
Thread Starter
Ok guys. Here's the latest: There's a light at the bottom of the voltage meter scale that should (I assume) come on with all the other warning lights when the ignition switch is in Position 2, yet doesn't come on. I took the gauge cluster apart and verified the contacts to around the bulb and verified that the bulb is good. My issue still persists with the alternator not putting out until I "blip" the throttle. I haven't had an opportunity to pull the back off the alternator and check the exciter wire and replace the voltage regulator (WYIT) yet. Too many other "honey do's).
05-04-2013, 05:08 AM
#20
Nordschleife Master
There's a little thin blue wire that is supposed to come off the alternator (IIRC, it is connected to the voltage regulator on the alternator) and go into your fusebox and eventually the dash cluster. Check to ensure that you have connectivity all the way on that little blue wire.
I rewired my racecar and had the same issues as you - the reason was I had the blue wire hooked up wrong.
I rewired my racecar and had the same issues as you - the reason was I had the blue wire hooked up wrong.
05-05-2013, 09:57 PM
#21
Drifting
Thread Starter
There's a little thin blue wire that is supposed to come off the alternator (IIRC, it is connected to the voltage regulator on the alternator) and go into your fusebox and eventually the dash cluster. Check to ensure that you have connectivity all the way on that little blue wire.
I rewired my racecar and had the same issues as you - the reason was I had the blue wire hooked up wrong.
I rewired my racecar and had the same issues as you - the reason was I had the blue wire hooked up wrong.
