Weird Charging Issue

[jlevie]

If tthe alternator is spinning fast enough, it may self excite, Otherwise it needs power to the exciter via the battery lamp. Start trouble shooting that circuit.

[spencer087]

is there a way to bypass he battery lamp? Like take wire a and splice to wire b to skip the bulb? The bulb is good but for some reason it isn't lighting up.

[spencer087]

or which wire on the alternator is the exciter wire??? Maybe ill work from there backwards

[jlevie]

The small wire to the alternator is the exciter.

[Ryann]

or which wire on the alternator is the exciter wire??? Maybe ill work from there backwards

Now you're thinkin'.

[spencer087]

I only see 2 connections to the alternator? One black one red with a smaller red wire going to it but uses the same connector as big red wire

[spencer087]

OK a discovery has been made!!! my old instrument cluster is a VDO P/N 1 377 313. THe temp sensor, odometer, and backlights dont work on it so i bought a used one which is a
MOTOMETER P/N 1 377 313
I bought based on part number.
My battery light on the old (VDO) cluster is a tiny light bulb labeled 12v 3w only
New cluster is a larger light bulb also labeled 12v 3w only
New cluster= everything works but car does not charge.
Old cluster= all sorts of issues but CAR CHARGES CORRECTLY and BAT LIGHT WORKS PROPERLY (on when key on off after start)

SO new question. WTF is with the same P/N cluster but one will not excite the alternator and one will???? How do i get my new cluster to excite the alternator properly???

[spencer087]

Both printed circuits terminate the light bulb to the same pins on the blue harness...
SO here's a test i ran.
took the small light bulb from old cluster and soldered it into the new cluster which normally has the larger light bulb.

Success!!!! (kinda)

After starting the vehivle the Battery light stays lit and voltage at the exciter is 1.6V until i move the throttle to 1000 RPM.

Then the bulb goes out and voltage at the exciter is 13.7 V.... Perfect!!!

Which also means i spent $190 on an alternator i didnt need. Awsome.

[bmwguy325is]

SO new question. WTF is with the same P/N cluster but one will not excite the alternator and one will???? How do i get my new cluster to excite the alternator properly???

Id say bad board in the cluster that doesnt let it charge. Try a third cluster they seem to be pretty cheap.

[spencer087]

FIXED!!!!

I took the smaller light bulb from the old cluster and soldered it into the new cluster that uses the bigger bulb and it works!!!

I guessing that the littler bulb had a different resistance thatn the bigger bulb which was throiwng the computer and wasnt allowing it to charge for some reason???

Anyways it works now and that makes me hapy!!!

I also fixed the ABS and BRake Lining lights. (Removed the bulbs and then made sure nothing jacked up by doing that LOL

[Ryann]

^Awesome man! Nice work.