Alternator died!

[lee]

you're welcome and for what it's worth, I agree with you on the lights. I doubt the wire change will do much if the system is clean, etc. I have done the mod, but that was because I was introducing a couple of audio amplifiers (at full tilt a 60 amp draw is possible for brief periods) and wished to make sure the system could handle the draw.

Perhaps I owe you an apology - I said earlier I didn't know what system the UK was using - if I could just learn to look a little closer at the location......Sorry (just another dumb American)

[Trevor]

Greetings Joe/Lee,

Just looked in here in the hope of finding something with shall I say " a little depth to it ".

Lee you are spot on with your comments. As a matter of interest here is an extract from one of my previous posts.

Quote : -

I have made measurements as follows using two high class digital instruments in parallel as a check on accuracy of calibration.

1. Voltage dropped alternator + to battery + . Dead flat battery and all lights and accessories drawing current, engine at 4500 rpm. --- 0.5 volts.

2. As above but with a fully charged battery (measured at 12.6 volts no load), --- 0.4 volts.

3. As 2, but with only engine electrics drawing current. -- 0.2 volts

4. As 1 above, but alternator frame to battery negative --- 0.13 volts

5. As 2 above, but alternator frame to battery negative --- 0.11 volts

6. As 3 above, but alternator frame to battery negative --- 0.08 volts

From the above the total voltage drop in the alternator to battery circuit can be summarized as ---

a, Conditions as 1 above, --- 0.63 volts

b. Conditions as 2 above, --- 0.51 volts

c. Conditions as 3 above, --- o.28 volts

Charging current based on the above can be calculated as follows ---

a. 0.63v / 0,008 = 78 Amps

b. 0.51v / 0,008 = 63 Amps

c. 0.28v / 0.008 = 35 Amps

I regard the above measurements as indicating that the charging system on my car i.e. OEM is working perfectly and this is born out by two trouble free years in my hands plus no indication of any repairs while in the hands of Japanese owners. It goes without saying that I will not be messing with it. If I do have trouble in the future I will be looking for the cause rather than by passing a fault. This is not the way to fix Ò crap connections Ò in the charging system.

There is an advantage in having a small resistance between the alternator and the battery as this can be a form of over current protection for the alternator. What is more any such small voltage drop will not effect the alternator output voltage as the electronic regulator senses battery voltage directly via a separate pilot wire.

My typing is too slow and arduous to explain this in detail but it is in fact illustrated within the above figures. It could be that Subaru designers had this in mind as I can not accept that they were trying to save on a few strands of copper or were ignorant in respect of basic Ohm's law.
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Joe, note that my measujrements as above confirm those put forward by Lee.

I would say forget the so called " alternator mod " and check for possible resistance in the loom to your lights. Check the voltage close to the bulbs and compare with that at the battery so as to establish possible voltage drop in the wiring and switch gear. This a likely fault if you do have a fault.

An accurate instrument is not essential as you are interested only in a comparison and a drop in voltage and not absolute figures. Stick a thin needle or pin through the insulated wire close to the lamp to take a reading. Measure comparing several earth points including direct to the battery as the return circuit could very well be faulty.

Best of luck and good wishes, Trevor *<)

[svxistentialist]

Originally posted by lee
you're welcome and for what it's worth, I agree with you on the lights. I doubt the wire change will do much if the system is clean, etc. I have done the mod, but that was because I was introducing a couple of audio amplifiers (at full tilt a 60 amp draw is possible for brief periods) and wished to make sure the system could handle the draw.

Perhaps I owe you an apology - I said earlier I didn't know what system the UK was using - if I could just learn to look a little closer at the location......Sorry (just another dumb American)

Dumb American? I don't think so!

Thanks Lee, and thanks Trevor.

No need to apologise Lee, what you said was correct, as backed up by Trevor's test figures.

Like Phil, my charging and starting circuits work like a dream, so I don't need or feel the need to tweak them.

Against that, the light output is only good enough for a 70-80 mph car, not nearly good enough for a 140 mph motor [not that I would be driving that fast on public highways ]

The real solution as I said before would be to change to glass headlights and uprate the bulbs. I would be very slow to go off-standard with bulbs while using the plastic lenses. When the lights are on, there is serious heat radiating through them, just feel the lenses. I have cleaned the outside of the lenses a fair few times with aggressive and fine polishes. It works, and it helps. However, I have not done the dismantling to clean the inner surface, primarily because the outer one degrades so soon. It would be a waste of effort. Glass is the way to go.

Thanks again for the advice.

Joe