Alternator issue
Discussion
I have a 2004 Ford with a 1.4 petrol duratec engine.
The car failed to start a few weeks ago which I put down to the battery being flat through lack of use. I took the battery out and charged overnight and the charger indicated the battery was OK. Refitted the battery the next morning and the car started fine. I drove for about an hour and stopped to do some shopping. The car refused to start on my return. I used a jump starter and drove the car back home with the battery light and ABS light on. Measuring across the battery terminals with engine running the voltage was under 10v.
Assuming that the alternator had gone, I got a cheap Lucas reman and fitted to the car. The car started fine but the battery light came on again. Voltage while running was 15.5V. I did a bit of searching and read about the smart charging system on the car. I unplugged the 3 pin plug on the alternator which I was led to believe would make the alternator default to 13.5v - 14v. It didn't and continued to output 15.5V.
At that point AI told me it was likely that the new alternator was faulty. So I fitted a more expensive Bosch one.
Unfortunately it's doing the same thing (actually 16.5V when 3 pin plug in, 15.5V when out).
Multimeter from casing of alternator to terminal shows 15.5V.
I'm loathe to believe that this alternator is also faulty, so before deciding, is there anything else I can check?
The car failed to start a few weeks ago which I put down to the battery being flat through lack of use. I took the battery out and charged overnight and the charger indicated the battery was OK. Refitted the battery the next morning and the car started fine. I drove for about an hour and stopped to do some shopping. The car refused to start on my return. I used a jump starter and drove the car back home with the battery light and ABS light on. Measuring across the battery terminals with engine running the voltage was under 10v.
Assuming that the alternator had gone, I got a cheap Lucas reman and fitted to the car. The car started fine but the battery light came on again. Voltage while running was 15.5V. I did a bit of searching and read about the smart charging system on the car. I unplugged the 3 pin plug on the alternator which I was led to believe would make the alternator default to 13.5v - 14v. It didn't and continued to output 15.5V.
At that point AI told me it was likely that the new alternator was faulty. So I fitted a more expensive Bosch one.
Unfortunately it's doing the same thing (actually 16.5V when 3 pin plug in, 15.5V when out).
Multimeter from casing of alternator to terminal shows 15.5V.
I'm loathe to believe that this alternator is also faulty, so before deciding, is there anything else I can check?
You don’t state what car but if it’s a fiesta they can sometimes suffer from a broken alternator control wire up by the bulkhead. Quickest test would be to start the car and measure the voltage to ground on the control wire at the alternator end with the alternator unplugged. If there’s nothing there then you need to trace the loom back.
LordLoveLength said:
You don t state what car but if it s a fiesta they can sometimes suffer from a broken alternator control wire up by the bulkhead. Quickest test would be to start the car and measure the voltage to ground on the control wire at the alternator end with the alternator unplugged. If there s nothing there then you need to trace the loom back.
The control wire is 0V. I'll check the fuse and if not, the wire.The bit I'm confused about is the fact the alternator puts out 15.5V when the plug is disconnected. Should it not default to around 13.5 ?
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