E30 m20 alternator charging issues.

[323e30 0]

back when I went to australia for a few months my father decided to play with my race car and fit a smaller japanese alternator so save weight, Had basically the same connections etc but it was never run with it as there was never a bracket made, Anyway I put back in a factory Alternator to get it running again

Puts out no charge at all,

Changed battery three times and have also changed the alternator twice (complete alternators),

Have checked all power cables and earths and they are connetcted correctly, Also made jumper earth and power leads to eliminate it completely as the fault. (also checked engine earth strap and rocker cover strap)

From what ive read the blue wire should only be for the cluster to say its charging, I do not get the red battery light on the dash at all. not even when the blue wire is connected to earth or when the key is first clicked on .

Anyone have any ideas what else could be wrong or where to look?

Do the clusters have any control over the alternator?

sick of seeing the car sitting in the garage and not too sure where to look next for faults.

[hotwire 352]

Blown charge warning light bulb??

To charge - the alternator needs:

Main battery feed

Earth - thru engine

Warning light connected to D+ on alt.

Light must come on with key on & obviously goes out when alt is charging. It relies on current draw of light with key on to "excite" the alternator on start up.

Generally a Bosch alt will self excite without a light but only with high initial revs - 3 -4k

[323e30 0]

Blown charge warning light bulb??

To charge - the alternator needs:

Main battery feed

Earth - thru engine

Warning light connected to D+ on alt.

Light must come on with key on & obviously goes out when alt is charging. It relies on current draw of light with key on to "excite" the alternator on start up.

Generally a Bosch alt will self excite without a light but only with high initial revs - 3 -4k

I checked the bulb and its fine but it doesnt come on when the ignition is switched, do you think the cluster unit could have anything to do with it?

Theres def earthing through the engine, even when i put a jumper lead from alternator housing to earth direct theres still the issue.

[hotwire 352]

I don't doubt the earth - wouldn't crank properly without.

Touch the blue W/L wire at the alternator to earth - should light the bulb. If it does - crook alt. If not - check wiring:-

Check the cluster - W/L needs ign supply to one side of bulb & other side comes out in a plug to the the blue wire leading to the alt. Earth that wire behind the dash & check for light - if not - problem inside. If it goes - problem in wire between dash & alt.

Never seen an internal fault in cluster to cause this scenario

[pureboiracer 0]

i had this problem with my racecar, The power supply wire into the cluster had no power so i just spliced it into an ign power wire, no more problems since. um i cant remember what the power wire is but the wire between the alt and cluster is blue, pin #17 i think, check that for continuity to the end of it at the altinator.

[323e30 0]

I don't doubt the earth - wouldn't crank properly without.

Touch the blue W/L wire at the alternator to earth - should light the bulb. If it does - crook alt. If not - check wiring:-

Check the cluster - W/L needs ign supply to one side of bulb & other side comes out in a plug to the the blue wire leading to the alt. Earth that wire behind the dash & check for light - if not - problem inside. If it goes - problem in wire between dash & alt.

Never seen an internal fault in cluster to cause this scenario

Yeah when I short the blue wire to earth the light does Not come on tried that earlier today. will check the wiring and try changing cluster ill post an update after

is the blue wire some kind of switching wire aswel as a warning Light?

[323e30 0]

Can i do anything to trick the alternator so its on all the time?

[pureboiracer 0]

Can i do anything to trick the alternator so its on all the time?

um im not too sure, try running an accessory wire to the blue wire, if yhe light doesnt come on when you short the blue wire make sure you have power into it, if you have a haynes book look at the cluster wiring diagram and you can work out what wire is meant to be the power wire.

[323e30 0]

um im not too sure, try running an accessory wire to the blue wire, if yhe light doesnt come on when you short the blue wire make sure you have power into it, if you have a haynes book look at the cluster wiring diagram and you can work out what wire is meant to be the power wire.

Yeah i figured i could try putting voltage on it but not sure if it needs a resistance or not, Cant find much info on google either, What do people with race cars do when they remove there cluster?

[Nobimmer 694]

Mine has no cluster either mike, haven't had any problems... yet.

[323e30 0]

Facelifts dont have the same issue only the 87 and older ones do. Ive even tried running a 5watt resisitor (5.8ohm) from the ignition to the exciter connection to imitate the cluster and the bulb , (with two diff alternators and 2 diff batterys) with still no love.

Really getting sick of it, any auto sparky pros out there want a cash job?

[hotwire 352]

As I said - E30 alt requires to operate:

It is a simplistic system:-

-Main battery supply

-Main earth (alt Body)

-W/light to excite (blue wire) Come on with ign & off when started & charging

If no light when earthing blue wire at alt - check at bulb holder in cluster - probe each side of holder with test light - look for 12v on one side & if bulb is good- probing other side will make w/l glow, if not - check bulb holder contacts.

Will have nothing to do with battery & as I said - with no w/l - alt (if good) will still excite with high revs

[323e30 0]

Yeah might just be having bad luck having a few dead alts in a row just strange as they were off good running engines, Everything tests fine, continuity from alt casing back to main earth is good less than 1ohm , get 11volts on exciter, (no bulb working) but only get the same 11volts on the output connection on the alternator (testing directly on terminal thread) have tried reving at 3000 but still looses charge and batt is def good as each time i jump start it it charges of the other car.

will try another alt tomorrow :s

[hotwire 352]

May have two problems - w/light circuit & alt

May need to rev beyond 3G for alt to self excite but if it is good it will self excite.

11 volts on w/light wire -disconnected from alt?? Makes no sense as if bulb is not working -blue wire should be open circuit.

Check warning light as I described earlier, if ok at dash - check dash plug & also at firewall plug.

[323e30 0]

replaced the alternator this morning and now its a runner, used a 90A facelift alternator rather than the 80A pfl one, pretty sure now that the last two alternators were just faulty. getting a good 13.6v

Still dont get the warning light on dash but that doesnt bother me.

[hotwire 352]

replaced the alternator this morning and now its a runner, used a 90A facelift alternator rather than the 80A pfl one, pretty sure now that the last two alternators were just faulty. getting a good 13.6v

Still dont get the warning light on dash but that doesnt bother me.

Good that you've sorted but strange that you had two crook alts that were suposidly good.

You should also trace & diagnose/fix the W/light circuit -it aint rocket science - no offence

[323e30 0]

Good that you've sorted but strange that you had two crook alts that were suposidly good.

You should also trace & diagnose/fix the W/light circuit -it aint rocket science - no offence

haha yeah I know I was seriously pulling my hair out because it was such a simple circuit, i have a feeling the cluster is no good, just being lazy because its fitted into a custom alloy dash so its a real pain to get in and out now.

Just stocked it good to drive finally.