EML does not flag a battery charging fault?

newstemp

Hello,

I am diagnosing a faulty charging system on a 2003 Ford Focus 1.6L Zetec SE. The relatively new battery has gone flat repeatedly, however can be recharged by another car or mains charger to the point of providing car starts again.

After start ~14V shows at the cigarette lighter socket so the alternator is charging the battery. However switching on substantial loads such as the front/rear demisters and the headlights can reduce this voltage to as little as 11V, so the battery is being drained. The car appears to have been discharging the battery when used several times a week in short town trips.

On the three pin alternator connector/harness, the red sense wire shows continuity to the battery terminal. There are also two wires, grey & blue, leading to the engine management module/ECU. I suspect that the alternator voltage regulator is malfunctioning.

I have two questions,

A. Any ideas on why the EML light did not stay on after ignition to register a low battery voltage/charging fault ?

B. Are there any other tests recommended before replacing the alternator or having it reconditioned ?

Thank you.


The alternator label shows,
MS1022118040
A115I-80A
MIC 3.2
24103/1
Q9K3B 98AB10300GK 14V

scannerd

do a diode test with multi meter. At 11v it may not be enough of a discharge to trigger the lamp.

If it is the regulator some can be replaced

enumbers

front heated screen will quite often drop voltage under 12v with other loads on at idle

newstemp

The alternator shows continuity across the main current supply wire to the battery, and the smaller red feedback wire. The internal socket voltage also goes up to ~14V (from ~12V engine off) without large loads indicating charging.

On a Mitsubishi Space Star II the voltage rarely drops below 13.5V and will usually increase to over 14V when large loads are switched on.

The battery has discharged several times, yet charged to over 12.6V out of the car, so correct charging in the car is not happening.

A common new voltage regulator (Manufacturer# 230790) is available for part#s 98AB10300GD/GE/GF/HE/JA/JB on the Ford Focus, and this also appears to be the correct part for the 98AB10300GK.

The Haynes manual even has a section on replacing the regulator and notes that at the time of writing Ford dealers do not supply the regulator as a separate part, so they recommend trying elsewhere. I will probably install a new regulator.

scannerd

Continuity test can be misleading as there is no load, suggest diode test any mutli meter can do, will give you more info on the heath of the alternator. Plenty of guides on youtube.

newstemp

I understand. I am awaiting a new DMM and will test the diodes when it arrives.