Instrument cluster light bulbs

[Synesthesia]

Which/What light bulb is for the battery/alternator in the instrument cluster? My lightbulb went out and i want to purchase the correct light bulb.

Thank you in advance.

[shogun]

as usual we need built year and month, as there were 3 different clusters installed over the production period. on my built year/month the battery bulb in the instrument cluster has 1.2W. 12V.
grey back plate http://bmwe32.masscom.net/sean750/da...usterBulbs.htm
white, here you can see that besides each bulb it is written on it for what it is http://bmwe32.masscom.net/billrickar...eringwheel.htm
use the ETK with your VIN and then you know exactly what you need to buy.
Maybe it is even not a bulb problem, but the wiring, on my M70 the alternator exciter wires comes up on left side engine bay with 2 more wires from engine oil level sensor and it is plugged in next to battery + post here http://bmwe32.masscom.net/sean750/sp...gConnector.jpg these thin cables sometimes break.
But even if the light in the cluster for the battery is bad, the alternator should work! Because there is a resistor https://www.bimmerforums.com/forum/s...light-resistor
info received from E32Fan: If the Alternator's field terminal goes open, then no current can flow through the idiot light lamp. The wiring diagram (Page 1230-00, -01) shows a resistor in parallel with the lamp at X16 pins 7 and 5, meaning that an open filament will not stop the field current. BMW engineers were not content to allow a blown idiot light filament to stop Alternator startup.

On my old grey backplate cluster the exciter wire is on plug X16 yellow, pin 5, blue wire, actually that is all the same on all clusters = grey, white, blue.
Is the blue cable connected correct to the alternator? See wiring diagram for your built year/model.

or you might visit one of the German car specialists in Hawaii for checking, they do not only service Porsche https://hi.pca.org/newsletter%20arch...001%20Aug.html
Maybe your alternator is not properly installed/connected wires, I remember you mentioned that you changed the alternator. See wiring diagrams https://shark.armchair.mb.ca/~dave/BMW/e32/
Cactuar made a good video, E32 735iL Remanufactured Bosch Alternator Installation https://www.youtube.com/watch?v=r5iBMJxACTs see from minute 2

[Synesthesia]

Wow. Thank you so much for the awesome information. The alternator was installed properly. However, when the car was running, there was no charge going to the battery. We made a direct connection from the alternator to the positive post in the engine compartment, and the battery finally read 14.1 volts. We noticed that the battery light did not light on when we turned the car on. So now the hunt begins. I hired a BMW certified technician to do the work. Thank you again.

[Synesthesia]

I have a '91 735iL, vin last digits is DC28991. Produced March of 1991. I checked that other member's post regarding his/her 535 battery problem. Shogun mentioned to check the instrument cluster bulb first. So am I wrong to not check the "exciter light" first? The last time I ran the car, it was at night. I turned on the headlights, then everything went dim. The battery light came on. Now, after a new battery and checking that the alternator (that was previously installed [OEM Bosch tag]) IS good, that battery light does not turn on at all.

[shogun]

in general it is designed that the battery/exciter light must be on when you switch ignition on and then go off when engine is running and the alternator is producing enough volts. The bulb is also a good indicator for other voltage problems of the alternator when the light is always dimming. Most older cars have a problem that the alternator does not work when the idiot light is not working, that is the reason I posted this back in 2009 https://www.bimmerforums.com/forum/s...rk-what-breaks
Then in 2015 in this thread it was found out that there is a resistor on the E32 charging/exciter system https://www.bimmerforums.com/forum/s...light-resistor and it was mentioned: "If the Alternator's field terminal goes open, then no current can flow through the idiot light lamp. The wiring diagram (Page 1230-00, -01) shows a resistor in parallel with the lamp at X16 pins 7 and 5, meaning that an open filament will not stop the field current" so basically on the E32 based on that statement in 2015 the system should work w/o working bulb. I have never tested it, so I cannot confirm this, but if I were you, I would fix the battery/exciter light that it works correct.

here is the wiring diagram for your March 1991 built 735iL https://shark.armchair.mb.ca/~dave/BMW/e32/e32_91.pdf check in section charging system 1230-....

[E32FAN]

in general it is designed that the battery/exciter light must be on when you switch ignition on and then go off when engine is running and the alternator is producing enough volts. The bulb is also a good indicator for other voltage problems of the alternator when the light is always dimming. Most older cars have a problem that the alternator does not work when the idiot light is not working, that is the reason I posted this back in 2009 https://www.bimmerforums.com/forum/s...rk-what-breaks
Then in 2015 in this thread it was found out that there is a resistor on the E32 charging/exciter system https://www.bimmerforums.com/forum/s...light-resistor and it was mentioned: "If the Alternator's field terminal goes open, then no current can flow through the idiot light lamp. The wiring diagram (Page 1230-00, -01) shows a resistor in parallel with the lamp at X16 pins 7 and 5, meaning that an open filament will not stop the field current" so basically on the E32 based on that statement in 2015 the system should work w/o working bulb. I have never tested it, so I cannot confirm this, but if I were you, I would fix the battery/exciter light that it works correct.

here is the wiring diagram for your March 1991 built 735iL https://shark.armchair.mb.ca/~dave/BMW/e32/e32_91.pdf check in section charging system 1230-....

Page 1230-01 shows the D100 Diagnostic Connector Pin 12. The pin numbers are molded into the connector, and you can see the X6002 pin numbering on Page 8500-16.

This is the D+ wire, the alternator Field coil. Current flowing into D+ excites the alternator to start generating voltage when spinning.

With ignition in Run (not start) the battery indicator should be lit. Measure the voltage at pin 12 - it should be less than 2 volts, say. When you Start the engine, pin 12 should rise to 13V and the indicator will be dark.

If the voltage at pin 12 is 12V in Run (engine stopped) then you can jumper pin 12 to GND and see the indicator light up. This would point to a wiring fault at D+, or a bad alternator.

So pin 12 gives us lots of clues, and it is very convenient to access

[Synesthesia]

IMG_6456.jpgThank you ALL for your help. Hwewwwww hopefully it's all finished. The problem with the alternator not charging the battery when running has been "temporarily" solved. There was a faulty wire somewhere in the dash. Even if this "garage queen" e32, with only 60K miles, the wires do get old and disintegrate. Just crossing my fingers now, hopefully I can just get this car's annual safety inspection. Then back to the garage. One advice I can learn from all this is to make sure your e32's battery is charged and in working order. Our e32's behave weird if its battery is not in good working order. Shogun and 32Fan thank you for the links and the advice. I will tackle the maintenance work when I can fit it between my family responsibilities. Aloha and Mahalo to you ALL.IMG_6457.jpg