Alternator/Charging issues

[redcar]

Hello all, after some help please regarding my e30 with m52 2.8 which has never had history of battery or charging issues and has run well for past few years.

Some background info:
- Alternator doesn't appear to be charging the battery.
- Battery has gone flat.
- Car starts when jump started but splutters and turns off when jumper cables are removed.
- All lights apart from the oil pressure light are illuminated on the instrument cluster when the engine is running/ignition on.

I have tested voltages i'm getting 10.9V at the big alternator stud and 0.9V at the little stud on the alternator (this is with engine running)

Would just like to confirm that it's the alternator which has gone bad before I potentially waste money on a new one.

Thank you in advance.

[Brianmoooore]

Check for a voltage between a clean, unpainted part of the alternator body and a good body earth, with the engine running, before finally condemning the alternator. I've told a little story on here before, where £400 had been spent on parts for a non charging problem (huge battery and alternator on an industrial vehicle), and although a new alternator had cured the problem, simply removing and replacing the original would have done the same hing, since the problem was corrosion between the aluminium and steel parts of the mountings.
If no voltage is found, then the chances are that the alternator has failed, but it's more than likely that the problem is just the regulator/brush pack, which is easily changed, probably without even removing the alternator from the car.

[redcar]

Hi Brian,

There is no voltage between the alternator and car body with engine running.
The voltage on little stud on alternator is now 5V whereas it was 1V before.
I did charge the battery up so perhaps this is the reason?

Ok will get a new alternator as this one whines a lot anyway.

Thank you for your help.

[milescook]

If your battery light comes on (which completes the circuit telling the alternator to charge) then it's not the stupid issue I had

[redcar]

Is it possible that the diode pack in my alternator may have failed? How do I test it?

Going to buy the bearings, voltage regulator and brush pack and refurb this alternator.

[redcar]

Bump - Help please, is there any need to change or a way to check the diode packs?

Thank you

[Brianmoooore]

I doubt if the diode pack is your problem.
An oscilloscope monitoring the output from an alternator will easily show up a duff diode, but in the absence of that, then opening the alternator up and checking the diodes individually with a meter switched to the appropriate setting is the way to go.

[DanThe]

Just fit another? They rarely go wrong, ive got a shelf full...

[Duncmasterflex]

If your battery light comes on (which completes the circuit telling the alternator to charge) then it's not the stupid issue I had

I had this issue at about midnight last night after fitting a reconditioned alternator and it still not charging- battery light not on, we took out the bulb and it was OK, but the o/S multiplug when wiggled and held down then put the light on and it charged, my speedo and mpg meter also started working, so the multiplug and clicks are now cable tied together and sitting at a funny angle so it charges until we figure out where the bad connection is! Nightmare

[Brianmoooore]

Plug on the back of the cluster? Soldered joints joining the socket to the PCB can crack if the plug is subject to rough handling. (Usually as a result of someone not working out how the locking mechanism works.)

[redcar]

Is it usual to have a very dimly lit battery warning light on the cluster? Changing my alternator and am experiencing this "issue" when engine is running.

[Brianmoooore]

Is it usual to have a very dimly lit battery warning light on the cluster? Changing my alternator and am experiencing this "issue" when engine is running.

Shouldn't be lit. You need to establish which way around the voltage across it is that is causing it to glow.
Measure the voltage across the bulb, noting which side is positive and which side is negative.

[redcar]

Ok will do, does that mean the alternator won't be working and charging my battery?

[Brianmoooore]

Alternator is working, but it may be overcharging or undercharging the battery, or it may be charging correctly and the fault is elsewhere.
Measure the battery voltage with the engine running and full beam headlamps on as well.

[redcar]

Alternator is working, but it may be overcharging or undercharging the battery, or it may be charging correctly and the fault is elsewhere.
Measure the battery voltage with the engine running and full beam headlamps on as well.

Will do and report back.
Thank you for the help Brian.

[Duncmasterflex]

Plug on the back of the cluster? Soldered joints joining the socket to the PCB can crack if the plug is subject to rough handling. (Usually as a result of someone not working out how the locking mechanism works.)

Thanks Brian, can I take the cluster apart and repair these broken solder joints?
Cheers
Dunc

[Brianmoooore]

Thanks Brian, can I take the cluster apart and repair these broken solder joints?
Cheers
Dunc

Easy job! Pull the coding plug out of the lower right front corner, remove all the screws at the back and prise the two halves apart.
While you're in there, check the soldering of a large resistor near the temperature gauge, which will have always deteriorated if not already attended to. Take out the SI board, put it in the freezer for ten minutes and measure the voltage across each battery, take out the speedo. assembly and check the soldering of the pins that connect it to the main board, and tighten the two small brass nuts on the back of the case.
Last job is to renew any of the bulbs that look blackened with age.

[Duncmasterflex]

Thanks Brian, can I take the cluster apart and repair these broken solder joints?
Cheers
Dunc

Easy job! Pull the coding plug out of the lower right front corner, remove all the screws at the back and prise the two halves apart.
While you're in there, check the soldering of a large resistor near the temperature gauge, which will have always deteriorated if not already attended to. Take out the SI board, put it in the freezer for ten minutes and measure the voltage across each battery, take out the speedo. assembly and check the soldering of the pins that connect it to the main board, and tighten the two small brass nuts on the back of the case.
Last job is to renew any of the bulbs that look blackened with age.

My word! Dunno if that'll be easy for a hamfisted wood butcher like myself, but hey I'll give it a go! ...or maybe give someone more competent
Thanks a lot mate, brilliant

[redcar]

Hello just reporting back on my findings;

Started car at voltage was 13.8V
Over the course of half an hour voltage down to 13V
With headlamps on the voltage went to 12.2V

With a charged battery connected with booster cables I'm getting
13.8v with engine running and 12.5V with engine running and headlights on.

What's the problem and how can I fix it please

Ive changed the alternator and it's from a supposedly working car.

Thank you

[Brianmoooore]

First thing I'd do is fit the charged battery in place of your existing battery, if possible, and voltage test again.
Where, exactly, were the car end of the booster cables connected?

[redcar]

Ok I'll do that but I suspect I'll get the same readings as I did when I had the battery connected with booster cables.

I have the battery in boot relocation and the booster cables were connected to the thick cable in the engine bay which is the dummy positive terminal. Earth was to the point on turret.

What do you suspect the problem is, another duff alternator?

[Brianmoooore]

The readings you were getting with the booster battery were as things should be.

I have the battery in boot relocation

I suspect this will be very relevant to the eventual solution!
If I'd known this earlier, I wouldn't have been so quick to condemn the first alternator, which is probably working fine.

[redcar]

The readings you were getting with the booster battery were as things should be.

I have the battery in boot relocation

I suspect this will be very relevant to the eventual solution!
If I'd known this earlier, I wouldn't have been so quick to condemn the first alternator, which is probably working fine.

Ok, sorry I'm a bit lost now.

What shall I test/do/change and what do you suspect the problem is?

Thank you Brian. Car is doing a trackday next weekend so really need it sorted soon.

[redcar]

With a know, working battery (big 110ah Bosch) in place of my existing battery (odyssey pc680) I'm getting 13.8v at the battery.

With the existing odyssey battery I'm getting 13v.

So has my odyssey pc680 battery had it?

The battery light is still dimly lit with either battery.

[Brianmoooore]

Don't get too excited yet. The battery you have fitted is fully charged, and might yet discharge to match the old battery.
Measure the voltage (if any) between the negative pole of the battery and the earth terminal on the top of the RH front suspension turret, with the engine running and lights on. (Clamp one end of a jump lead onto the turret and connect your meter wire to the other end of the jump lead, so that you can reach the battery pole with the other meter lead.)

[redcar]

Hi Brian. Did what you said an I'm getting 0V between battery negative and suspension turret.

Gave my odyssey battery a charge and recondition and started car just now
Getting 13.2 at battery with engine off. 14V with engine on. 13.9 with engine on and lights on.
These readings are measured from the battery itself which is in the boot.

Battery warning light is still dimly lit.

What's the next step from here

[redcar]

Here's a photo of the dimly light battery warning light.

[redcar]

Hello, any more help with this please or should I just buy a new odyssey battery?

Thank you.

[Brianmoooore]

Your battery in the boot conversion should consist of a negative connection to the battery, with that lead firmly bolted to clean bodywork, and two wires from the positive pole of the battery, running to the engine bay.
What, exactly, have you connected each of those two wires to at the front?

[redcar]

The little wire from the positive pole of battery goes to the engine bay and is connected only to the ECU 12v.
The large wire from the battery is connected to fusebox, engine loom 12v (starter/alternator) and something else I think.

Should I order a new battery as need to use car on weekend and need the parts to arrive in time if i require them.

Thank you.

[DanThe]

Have you pulled the permanent live wires (Red) apart in the loom then? The engine loom live cable feeds the whole of the engine loom minus the coils

[Brianmoooore]

Are you 100% sure that the ECU is connected to the smaller wire, and not the fusebox?
Transposing these wires could conceivably cause what you are getting.

[redcar]

Have you pulled the permanent live wires (Red) apart in the loom then? The engine loom live cable feeds the whole of the engine loom minus the coils

sorry I'm not really sure what you mean. Could you clarify please?

The engine loom is connected to the big dummy positive terminal in the engine bay. The fuse box is also attached to this.

The ecu live is connected to the thinner wire coming from the battery into the engine bay.

[redcar]

Brian, I will double check again when I'm home.
There could be a chance I'm wrong about this.

Am I correct in thinking there should be absolutely no light on that battery warning lamp?

[DanThe]

Would be easier if you posted pictures of your setup

The ECU live wire is part of the whole engine loom permanent live circuit, powers everything except the coils, so if you have the engine loom connected to the large wire from the battery it is wired wrong, you would have to cut the loom apart to do this.

What I think you mean is you have the E36 fusebox and starter power wires connected to the large wire to battery