Alternator Load Dump
I have a pushbutton/lever type of 140 amp circuit breaker on my 120 amps alternator to house battery feed. Not Bussman or Bluseas brand = Mistake. After less than 5 minutes of 70 to 90 amp...
Forum Discussion
I got the term 'load dump' from MexicoWanderer.
He also basically walked me through this voltage regulator modification.
What I would do differently, well I would not order the 10 ohm 50 watt resistor and pay nearly 30$ for it, when a 50 watt 10 ohm resistor can be had for under 5$. The resistance of the 'field replacement module' was an unknown at the time however. This tricks the ECM into believeing that it is still hooked to the alternator, and into not flashing the check engine light.
I'd likely order a 10 ohm 100 watt resistor instead of the 50 for a fraction of the price I did pay. I added heatsinking to the 50 watt and all appears well a year later. It does get hot and manupulating voltage does change the ampoerage passing through the resistor, though I have not done the full battery of tests at different outputs, just put my clampmeter over a wire and dialed voltage up and down.
Function wise, There is some voltage sag as the wiring/connectors heat up. I took power for the A terminal( always on) from the alternator + stud, which then goes to circuit breaker then battery switch via doubled 6awg, then 2awg to battery terminal. Ideally this A terminal wire would be 12AWG right to battery terminal.
This doubled 6awg is an old set of jumper cables. I will replace this with 2 or 1 AWG at some point, and then the voltage sag should be less.
Before the possibility of tricking the engine computer with the resistor, I was considering influencing voltage with a DC to DC booster, but was not quite sure it would not cause the VR in the ECM to fry. I was trying to determine when and why the VR was choosing the voltages it did, as it occassionally would rocket back to 14.9v for no discernable reason.
I was always extremely irritated when the ECM's VR would choose 14.9 or 14.7 of a battery already fully charged, and than choose 13.7 on one still far from fully charged.
Now of course I choose voltage. With the dashboard digital Ammeter now reading amps into battery I basically choose 14.7v, until I know for sure the battery is full. In daytime, I can lower voltage to below my solar float setpoint of 13.6v, and the alternator amperage can goto zero as the solar provides the 8.2 amps required to run engine at idle or the 12.2 amps at 2000 rpm.
I will adjust voltage slightly for battery temperature too.
The turns counter is not really so helpful as 14.7v when battery is depleted is not the same as when it is full, but perhaps thicker copper will narrow the gap. This appears to stretch a bit more than when first installed too, so I rarely ever look to see what the turns counter reads. I'd have no issues with a non turns counting 10 turn potentiometer.
With voltmeters right next to ammeter and potentiometer, it is so easy to adjust I am not worried about the turns counter not being exact or repeatable at different amperage outputs.
50 amps max at hot idle is a factor the voltage regulator cant overcome when the loads are 60 amps. I usually can crank up the voltage at hot idle and get it to the higher voltage( field current goes way up and so did VR temperature before fan), but then when I accellerate voltage will jump well past 14.7v, and more than 30 seconds of 14.7v+ when the ECM would have chosen 13.7v fires off the check engine light and goes into limp home mode where MPG suffers until I reset the ECM by removing power. The CEL will go out on its own if I lower voltage and restart engine, but the limp home sensor settings stay active until ECM is reset.
When my 140 amp breaker tripped at sub 110 amps, It was not my first thought, and I kind of assumed the VR itself was somehow responsible, or had lost power. I drove several miles with headlights on and a battery depleted well below 50% and voltage 11.9v or so.
The I terminal is for the switched ignition 12v, and I found a wire under the dash which becomes live only after engine start. I thought this might have blown an OEM fuse so I checked those first.
But this wire also powers the fan I have attached to the heatsink on the VR, and this was still turning on after starting engine. I then probed the A terminal and found no voltage, then scolded myself for not immediately checking the 140 amp breaker.
My 14 awg fusible link on my OEm cabling was installed by an auto electric shop, whom I assume had no 10AWG fusible link, back in 2005 or so. Back then my 40/90 alternator failed and I replaced it with a 50/120, and did not charge my batteries before starting engine. The original needle ammeter went higher than I ever had seen before, and then went neutral. I was unaware of the fusible link's failure, but the Sparkies zeroed in on it immediately.
Strangely the original 10AWG link did not blow as designed, and still tested fine , with no load.
I've been meaning to properly replace it, but with the parallel circuit it has not been an issue since.
I did use 14 or 12AWG wire to the I terminal of the voltage regulator, but this wire carries so little current this was several degrees of overkill.
So overall I love the modification, and it is working quite well, even with the voltage sag at high amperages. It can be improved with thicker copper.
As for tricking an internally regulated alternator, I do not know how one bypasses the internal VR and wires up an external VR like the transpo540HD in its place.
Tricking the ECM and installing the 540HD on an externally regulated alternator is likely cakework in comparison to modifying an internally regulted alternator for external regulation.
Lance neville 8MR external regulation modification
What I really love about the VR modification is I can stop the belt squealing when cold and wet by lowering the voltage, and of course I can now visibly see the difference in amperage the battery accepts at different chosen voltages. 3x more amps at 14.7v vs 13.7v is not insignificant.
He also basically walked me through this voltage regulator modification.
What I would do differently, well I would not order the 10 ohm 50 watt resistor and pay nearly 30$ for it, when a 50 watt 10 ohm resistor can be had for under 5$. The resistance of the 'field replacement module' was an unknown at the time however. This tricks the ECM into believeing that it is still hooked to the alternator, and into not flashing the check engine light.
I'd likely order a 10 ohm 100 watt resistor instead of the 50 for a fraction of the price I did pay. I added heatsinking to the 50 watt and all appears well a year later. It does get hot and manupulating voltage does change the ampoerage passing through the resistor, though I have not done the full battery of tests at different outputs, just put my clampmeter over a wire and dialed voltage up and down.
Function wise, There is some voltage sag as the wiring/connectors heat up. I took power for the A terminal( always on) from the alternator + stud, which then goes to circuit breaker then battery switch via doubled 6awg, then 2awg to battery terminal. Ideally this A terminal wire would be 12AWG right to battery terminal.
This doubled 6awg is an old set of jumper cables. I will replace this with 2 or 1 AWG at some point, and then the voltage sag should be less.
Before the possibility of tricking the engine computer with the resistor, I was considering influencing voltage with a DC to DC booster, but was not quite sure it would not cause the VR in the ECM to fry. I was trying to determine when and why the VR was choosing the voltages it did, as it occassionally would rocket back to 14.9v for no discernable reason.
I was always extremely irritated when the ECM's VR would choose 14.9 or 14.7 of a battery already fully charged, and than choose 13.7 on one still far from fully charged.
Now of course I choose voltage. With the dashboard digital Ammeter now reading amps into battery I basically choose 14.7v, until I know for sure the battery is full. In daytime, I can lower voltage to below my solar float setpoint of 13.6v, and the alternator amperage can goto zero as the solar provides the 8.2 amps required to run engine at idle or the 12.2 amps at 2000 rpm.
I will adjust voltage slightly for battery temperature too.
The turns counter is not really so helpful as 14.7v when battery is depleted is not the same as when it is full, but perhaps thicker copper will narrow the gap. This appears to stretch a bit more than when first installed too, so I rarely ever look to see what the turns counter reads. I'd have no issues with a non turns counting 10 turn potentiometer.
With voltmeters right next to ammeter and potentiometer, it is so easy to adjust I am not worried about the turns counter not being exact or repeatable at different amperage outputs.
50 amps max at hot idle is a factor the voltage regulator cant overcome when the loads are 60 amps. I usually can crank up the voltage at hot idle and get it to the higher voltage( field current goes way up and so did VR temperature before fan), but then when I accellerate voltage will jump well past 14.7v, and more than 30 seconds of 14.7v+ when the ECM would have chosen 13.7v fires off the check engine light and goes into limp home mode where MPG suffers until I reset the ECM by removing power. The CEL will go out on its own if I lower voltage and restart engine, but the limp home sensor settings stay active until ECM is reset.
When my 140 amp breaker tripped at sub 110 amps, It was not my first thought, and I kind of assumed the VR itself was somehow responsible, or had lost power. I drove several miles with headlights on and a battery depleted well below 50% and voltage 11.9v or so.
The I terminal is for the switched ignition 12v, and I found a wire under the dash which becomes live only after engine start. I thought this might have blown an OEM fuse so I checked those first.
But this wire also powers the fan I have attached to the heatsink on the VR, and this was still turning on after starting engine. I then probed the A terminal and found no voltage, then scolded myself for not immediately checking the 140 amp breaker.
My 14 awg fusible link on my OEm cabling was installed by an auto electric shop, whom I assume had no 10AWG fusible link, back in 2005 or so. Back then my 40/90 alternator failed and I replaced it with a 50/120, and did not charge my batteries before starting engine. The original needle ammeter went higher than I ever had seen before, and then went neutral. I was unaware of the fusible link's failure, but the Sparkies zeroed in on it immediately.
Strangely the original 10AWG link did not blow as designed, and still tested fine , with no load.
I've been meaning to properly replace it, but with the parallel circuit it has not been an issue since.
I did use 14 or 12AWG wire to the I terminal of the voltage regulator, but this wire carries so little current this was several degrees of overkill.
So overall I love the modification, and it is working quite well, even with the voltage sag at high amperages. It can be improved with thicker copper.
As for tricking an internally regulated alternator, I do not know how one bypasses the internal VR and wires up an external VR like the transpo540HD in its place.
Tricking the ECM and installing the 540HD on an externally regulated alternator is likely cakework in comparison to modifying an internally regulted alternator for external regulation.
Lance neville 8MR external regulation modification
What I really love about the VR modification is I can stop the belt squealing when cold and wet by lowering the voltage, and of course I can now visibly see the difference in amperage the battery accepts at different chosen voltages. 3x more amps at 14.7v vs 13.7v is not insignificant.
