Bypassing Voltage Regulator?
01-08-2013, 02:39 PM
#1
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Bypassing Voltage Regulator?
Hi, I have been having an electrical issue with my 99 XJ. I get a reading of 18.25-19v.
Replaced the PCM, Alt. Ground and Pos cables, cleaned all contacts, checked all associated wires and all tested fine.
I cannot think of what else it could be affecting the charging system so I was thinking of just bypassing it altogether and having an alt. output a consistent 14v.
Is this possible? would I just have to install an internally regulated alt.? Or could I attach an external regulator in-between the alt. and batt?
Replaced the PCM, Alt. Ground and Pos cables, cleaned all contacts, checked all associated wires and all tested fine.
I cannot think of what else it could be affecting the charging system so I was thinking of just bypassing it altogether and having an alt. output a consistent 14v.
Is this possible? would I just have to install an internally regulated alt.? Or could I attach an external regulator in-between the alt. and batt?
01-08-2013, 05:04 PM
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Hi, I have been having an electrical issue with my 99 XJ. I get a reading of 18.25-19v.
Replaced the PCM, Alt. Ground and Pos cables, cleaned all contacts, checked all associated wires and all tested fine.
I cannot think of what else it could be affecting the charging system so I was thinking of just bypassing it altogether and having an alt. output a consistent 14v.
Is this possible? would I just have to install an internally regulated alt.? Or could I attach an external regulator in-between the alt. and batt?
Replaced the PCM, Alt. Ground and Pos cables, cleaned all contacts, checked all associated wires and all tested fine.
I cannot think of what else it could be affecting the charging system so I was thinking of just bypassing it altogether and having an alt. output a consistent 14v.
Is this possible? would I just have to install an internally regulated alt.? Or could I attach an external regulator in-between the alt. and batt?
01-08-2013, 05:58 PM
#3
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You replaced the PCM, AND the alternator and it's still 19V? (another guy just posted he was over volting about the same). Like Bob said,,you know you can get a remotely decent DVM at Harbor Freight for $5. I sure don't get that. Wiring connections and grounds are always an issue. Probly much more often the culprit when the problem makes no sense.
I'd hazard a guess the PCM gives the Alt current, or a signal to control the strength of the magnetic field the spinning rotor is making. (that's how it regulates the voltage)
Checking what is in that wire might make sense. Codes? (I guess they read them free at the auto parts).
Also, the speed of the blinker is a last resort voltage "signal" Yours must be flyen!
I'd hazard a guess the PCM gives the Alt current, or a signal to control the strength of the magnetic field the spinning rotor is making. (that's how it regulates the voltage)
Checking what is in that wire might make sense. Codes? (I guess they read them free at the auto parts).
Also, the speed of the blinker is a last resort voltage "signal" Yours must be flyen!
01-08-2013, 06:25 PM
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Hey, Offroad...do you happen to know, does the PCM "provide" field current, or controls something in the Alt. that does it? (in a 99)
I do think at least a few amps are needed in the rotor for the outer stator to make much AC. (then the probably 6 diodes make that into DC)
I do think at least a few amps are needed in the rotor for the outer stator to make much AC. (then the probably 6 diodes make that into DC)
01-08-2013, 06:33 PM
#7
Here ya go....
ELECTRONIC VOLTAGE REGULATOR
DESCRIPTION
The Electronic Voltage Regulator (EVR) is not a
separate component. It is actually a voltage regulating
circuit located within the Powertrain Control
Module (PCM). The EVR is not serviced separately. If
replacement is necessary, the PCM must be replaced.
OPERATION
The amount of DC current produced by the generator
is controlled by EVR circuitry contained within
the PCM. This circuitry is connected in series with
the generators second rotor field terminal and its
ground.
Voltage is regulated by cycling the ground path to
control the strength of the rotor magnetic field. The
EVR circuitry monitors system line voltage and battery
temperature (refer to Battery Temperature Sensor
for more information). It then compensates and
regulates generator current output accordingly. Also
refer to Charging System Operation for additional
information.
DESCRIPTION
The Electronic Voltage Regulator (EVR) is not a
separate component. It is actually a voltage regulating
circuit located within the Powertrain Control
Module (PCM). The EVR is not serviced separately. If
replacement is necessary, the PCM must be replaced.
OPERATION
The amount of DC current produced by the generator
is controlled by EVR circuitry contained within
the PCM. This circuitry is connected in series with
the generators second rotor field terminal and its
ground.
Voltage is regulated by cycling the ground path to
control the strength of the rotor magnetic field. The
EVR circuitry monitors system line voltage and battery
temperature (refer to Battery Temperature Sensor
for more information). It then compensates and
regulates generator current output accordingly. Also
refer to Charging System Operation for additional
information.
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01-08-2013, 11:11 PM
#10
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I'll be dipped. That makes it sound like the PCM is controlling the ground of the field circuit. (same as any old (actual generator), They controlled field strength by varying resistance to ground.)(alternators make AC, which is rectified by the diodes). (and normally the field is energized)
So if the "control" wire from the Alt to the pcm grounded anywhere, voltage would shoot up high.
Yea, maybe both you and that other guy with 19 volts might both apply a meter to the bat, and also make sure the control wire to the Alt. is not grounding.
So if the "control" wire from the Alt to the pcm grounded anywhere, voltage would shoot up high.
Yea, maybe both you and that other guy with 19 volts might both apply a meter to the bat, and also make sure the control wire to the Alt. is not grounding.
Last edited by DFlintstone; 01-10-2013 at 01:31 AM.
01-09-2013, 12:46 AM
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I believe Chrysler EVR modulates the field ground in a PWM type fashion. It's pulsed, wider pulses = higher output voltage. So yeah, if the control line is grounded somewhere the alternator runs flat out.
Last edited by Radi; 01-09-2013 at 12:49 AM.
01-10-2013, 01:47 AM
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Mike, sometimes a wire going around an edge grounds underneath where you can't see. The "loom" might split of wear through. Cruiser has mentioned jiggling wires while monitoring them. I might hook a DVM to the battery and just poke around...idleing, (radio fuse out), and watch. Have a friend watch it while you get in there and move things. See if you can move anything that changes the meter reading.
(I only mention the radio because I fried one once)(was my 12 volt house. 60 waz too much)
(I only mention the radio because I fried one once)(was my 12 volt house. 60 waz too much)
Last edited by DFlintstone; 01-10-2013 at 01:50 AM.
01-10-2013, 02:00 AM
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Oddly enough, I have never seen an ALT actually push over 15volts. I don't see in the posts about using a DMM on the car to see what the battery actually is at. I don't think that alternator even at full bore will push 15 volts, most alternators fry because of AMP's not volts. I would put money on the fact that you might have a bad wire to the gauge or a bad gauge cause I strongly doubt you are running 18-19 volts.
03-01-2019, 04:38 AM
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If you are using a cheap DMM, make sure you use another better one as well... I spent 2 days scratching my head over the 18-19 volt thing, thought my battery was over charging the system. Turned out to be a bad multimeter... the I was on to my short problem again.. sometimes it’s the simple things I guess. Lol just wanted to put that out there for the less experienced folk. Cheers 🍻