Hi guys, alternator was blowing the 60 amp fuse continuously, after checking all wires and doing the alternator test at the shop the problem was 100% from the voltage regulator at the PCM .
We installed an external regulator on the alternator and everything went fine except the check engine light staying on even after resetting from obd.
Anyone succeed in fixing the check engine light after an external alternator regulator install?
Thank you

 

the voltage regulator should be built in to the alternator... so Im not sure what you bypassed. Also what 60 amp fuse were you blowing. Should have found the exact issue and replaced it to Oem instead of trying to band aid a issue and create more problems.

Go to Auto Zone or another auto parts store and have them scan for the code its throwing then come back to us.

 

The alternator voltage regulator on xj 1994 is built in the computer. The fuse blowing was the alternator one.
When an external alternator regulator installed on the alternator itself it is Normal that the check engine comes on coz the one in the computer is disconnected and no more in use. The computer see this faulty and throw a code.
I searched and read this issue of fuse blowing and this is the best fix I could do. The other fix is to replace the computer. I'm In Beirut Lebanon not in the US

 

My CEL has been on for two years now for a different reason, I ignore it and wait for it to burn out.

 

I can shut it down for good but I won't get warnings if smtng else goes wrong.

 

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 (B+) and
battery temperature (refer to Battery Temperature
Sensor for more information). It then determines a
target charging voltage. If sensed battery voltage is
0.5 volts or lower than the target voltage, the PCM
grounds the field winding until sensed battery voltage is 0.5 volts above target voltage. A circuit in the
PCM cycles the ground side of the generator field up
to 100 times per second (100Hz), but has the capability to ground the field control wire 100% of the time
(full field) to achieve the target voltage. If the charging rate cannot be monitored (limp-in), a duty cycle
of 25% is used by the PCM in order to have some
generator output. Also refer to Charging System
Operation for additional information.


Looks like you have to put up with it or get a new PCM

 

Thanks. I attached an external voltage regulator on the alternator and it worked fine. Now I'm trying to bypass the check engine light. Installing a diode on the pcm alternator wire are it think voltage drawing is done. let's see if it will work.

 

Hello friend do You solve the battery light ?

 

I have a 91 Laredo, started having a voltage drop at about 2100 rpms. I have had both battery and alt problems. Have since replaced both, neither has solved problem need advice on installing external voltage regulator