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Originally Posted by dannmarr
Why is the "alternator upgrade" wrongly recommended? All it's doing is adding
an additional path for the amperage to flow, correct?  |
The Alternator “upgrade ?" Modifications.
Look for the cause rather than by passing a fault. Making modifications is not the way to fix “ crap connections “ in the charging system.
If you are running a special alternator capable of delivering increased current you are in a different ball park, but you should think very seriously about the need to incorporate suitable fuse link close to the battery connection.
It must be appreciated that the alternator wiring mod as originally suggested by passes all alternator over current protection as has been incorporated in the original set up for very good reason. There has been a thread where this factor appears to have caused alternator damage.
In the event of a front end prang and a short circuit at the alternator you could end up with an engine compartment fire as this circuit is capable of passing a very high fault current. If your insurer’s assessors are on the ball you will be out of luck in a big way should you make an insurance claim.
Provided the original alternator wiring, grounds included and all connections are in good original condition there should be no problem. If a problem does exist and the original wiring or connections are suspect, it is a simple matter to locate exactly where there is resistance in the circuit, including the ground points, which could be dropping the output voltage from the alternator.
Connecting a volt meter across a resistance/conductor measures the voltage dropped as current passes through the resistance/conductor, as well as the associated connections, if the test probes are in contact with the first point in the circuit, e.g. the terminal bolt, screw, battery post ot whatever. With the suspect circuit under full load, a volt meter test probe against each end of the suspect wire or connection will record any voltage drop. After the first check with the meter set at the circuit voltage, as a matter of meter safety, the lowest range available can be selected.
There can be 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 small voltage drop will not effect the as designed alternator output voltage, as the electronic regulator senses battery voltage directly via a separate pilot wire. It could be that Subaru designers had this in mind, as it is hard to accept that they were trying to save on a few strands of copper or were ignorant in respect of basic Ohm's law.
The often reported simultaneous illumination of several trouble lights is due failure of diodes in the alternator. As a result an alternating current is superimposed on line and this bypasses blocking diodes in the circuit to the trouble lights thus energising them.
I have checked the original alternator wiring on my car and these figures can be taken as typical and indicative. Measurements were taken, using two high class digital instruments in parallel, as confirmation of the accuracy of calibration.
1. Voltage dropped alternator + to battery + with 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 circuits can be summarised 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 seven 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.
Take it or leave it, I have no further comment. I am trying to be helpful rather than controversial.