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Good afternoon, here is the information you requested:
The Electronic Voltage Regulator (EVR) is not a separate component. It is actually a voltage regulating circuit located within the Powertrain Control Module (PCM....engine computer) 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.
That doesnt say to much accept just confuses the situation further. The way it should be checked is using a multimeter, check the voltage reading at the battery while the engine is running. You should show around 13.5 volts or higher. If this checks okay then you need to hook up a scanner and access the engine controller and see what the charging voltage is at the controller. If this is okay and varified to be very close to the readings taken at the battery then you need to start checking at the instrument cluster. You can access the cluster as well with the correct scanner and may be able to see what the information from the engine controller is so as to varify that the reads are the same. This would let us know where the problem may be such as cluster showing the 13.5 battery reading from the engine controller when accessed with the scanner and the guage still not working. That would point to a bad cluster. I assume you have no other problems except for the guage reading? If you have issue such as the battery going dead and the reading at the battery while running not being correct then the issue will be else where.
If it reads 13.2volts while running at the battery then the actually charging system is working correctly. If it reads 13.2 at the battery but nothing inside on the guage as you described then the issue is most like a guage issue which would need to be checked further to see if the controller or guage is the issue. Some cluster had a self test feature that you could try to see if all guages worked. It just depends on the year and make of vehicle. What you could try is with the key off, hold down the trip reset button on cluster and keep holding it and then turn the key on to the run postion (not start position) and then once the lights start coming on...release the trip button and watch to see if all the guages start to move and go thru the self test.
no cold air blowing out when ac is on but low pressure