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Ironmike, Ford Technician
Category: Ford
Satisfied Customers: 3377
Experience:  30 years ASE Master tech L1 . Ford master
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i have a ford focus 2001 batterie light on, new alternator

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i have a ford focus 2001 batterie light on, new alternator and batterie light still on, voltage output at batterie is 13,9 volt. what could it be


Check the one wire connector(small red) at the back of the alternator. I had one that gave me a hard time and the wire was hanging on by a thread, fixed the wire and done.

good luck

Customer: replied 6 years ago.
i did check red wire and i still have the same problem, the light goes on after 1-2 min of running do you have something else that could help me out
The alternator is comtrolled by the pcm(computer) you will have to scan the computer to see what is happening. Light could be on because of a bad diode and you are getting back feed. Other than that the pcm might be the issue. I would want to see the car on a ford scanner.
Customer: replied 6 years ago.
could this affect the idle on the car because since the new are on the car when it comes at idle it dies but you heve no problem restsrting and when i do check the voltage at the output i still have 139 to 14 volt ouput

if the pcm is the trouble it could be. need to check for codes

Customer: replied 6 years ago.
no trouble code, could it be that cam sensor has failed and its just a bad coincidence of a ford, because when driving the car on the highway it goes very good even if the light of the battery is on
it could charge and still have an issue and set no code like i said. If there is back feed or a pcm issue. If you have or had a bad cam sensor it would set a code. Let me do some more research.
Customer: replied 6 years ago.
ok i will wait for an answer and i do appreciate your help this bizarre problem

here is the system description. This problem we have is related to the idle.Have youn checked the battery to see if it has a dead cell and that it can hold a load?

The Powertrain Control Module (PCM) -Controlled charging system (Figure 142) provides many additional benefits over the current Integral Generator Regulator system. The first benefit is improved battery life. In an integral generator regulator system, the regulator set point is established by a temperature sensor in the regulator which estimates battery temperature. Field data has shown this approach lacks accuracy. With a PCM-controlled generator, the regulator voltage set point is determined by the PCM and communicated to the regulator via the generator communication line. The PCM will use a calibratable algorithm to estimate battery temperature. Improving battery temperature estimates will reduce battery damage caused by over- and undercharging.

The second benefit is improved engine performance. Whenever the PCM senses a Wide-Open Throttle (WOT) condition, the PCM will momentarily lower the regulator voltage set point. This reduces the torque load of the generator on the engine and improves acceleration. The PCM has a calibratable time limit on this reduced voltage feature. This is to prevent the generator output from being cut back for an extended WOT period, which could cause battery discharge.

The third benefit is improved idle stability. In response to the PCM's generator communication signal, the regulator uses a generator monitor signal to provide feedback to the PCM. The generator monitor signal provides the PCM with charging system information. Specifically, it lets the PCM know when the charging system receives a transient electrical load which would normally affect idle stability. Because the PCM can anticipate additional loads, actions can be taken to minimize idle sag. The PCM can choose to either reduce the regulator set point or increase engine idle speed, both of which are calibratable features. In order to establish whether the regulator is accurately maintaining the desired voltage set point, the regulator uses a charging system voltage line to sense battery voltage at the rear power distribution box.

The fourth benefit is reduced cranking efforts. The PCM can reduce the mechanical load on the starter by initially commanding a low voltage set point. This may improve start times.

If the PCM detects a charging system error, it will broadcast a low voltage telltale (ON) command which tells the cluster to light the charge indicator. The charge indicator will be illuminated it the PCM fails to see a signal on the generator monitor line for a time period greater than 500 milliseconds . This telltale command will also be used to indicate over-voltage conditions detected by the PCM controlled generator.

Each time the ignition switch is cycled to the run position, the cluster will initiate a bulb check by illuminating the charge indicator. It is the PCM's responsibility to issue a low voltage telltale (OFF) command if the charging system is functioning properly. This message should be sent during Network Initialization in the voluntary phase (250 milliseconds to 450 milliseconds after the ignition switch is cycled to the run position). If a low voltage telltale (OFF) command is not received by the cluster, the cluster will continue to light the charge light indefinitely.

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Customer: replied 6 years ago.

when I ll get the problem solved, I will let you know so this could help others like me

thanks again

we have to have a wire or connection issue that is throwing the ecu off. You have to check the wires going to the alternator and to the ecu and the other power wire to the fuse, ohm them out. This issue is also on the diesel version.
A2 - A5

A5 - A7
Customer: replied 6 years ago.

yesterday i did put a new alternator on and it solved all the problems on the car . i told myself i will get bthe battery light repatr at first then i will look for the other problems but iy did solved all the rest. i really think that when a diode is burnt in the alternator it will affect the pcm itself. I know its weird but now the car works like a charm

thanks for the help you gave me.



and good holiday season fr

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