I have had two instances where charging failed yet there was no warning on the dash. First was a Kangoo whose alternator failed when the bearing broke up and took out the rectifier and then yesterday on my pug 206 the fan belt snapped, first indication was the lost of steering. On neither did a warning light come on, on older cars the ignition warning light would come on if charging was lost, why this change?
AJH
I have occasionally seen failure of the warning bulb, the alternator cannot start charging without the bulb at low speed, but will kick in when revved enough, so you may get away with no warning light for some time. (same thing for broken warning light lead, or corrosion on its connection. AFAIK all cars/vans do have charge warning lights as standard. certainly the kangoo and the 206 has one, but both are controlled by extra nodules rather than direct off the alternator as in the past.
There can be certain alternator problems where it ceases to give any meaningful charge, but the warning light doesn't come on. But its drive belt failing isn't one of them. Are you sure it was the same belt driving the alternator as steering?
Drivers do not check for lights that don't come on, these days a plethora of lights self check, and one or two missing is not obvious. In the old days of just two lights it was easier to spot a missing one. I come across about two cars a year with a defunct oil warning light, yet the owner has not noticed and is surprised when I fix it and tell them. I look for it after changing the oil, just to make sure all is circulating before checking the level again. My first check on a suspected non charging car is the warning light situation, then the belt, then I get the meter out. Most often nowadays it is a battery fault rather than a charging fault.
All true. But if the warning bulb had blown, be obvious when you switch on?
The days when a diesel would get you home without any battery power whatsoever have long gone.
Six months ago I started my Focus 1.8 TDCI and there was a squeal, like a slipping belt, which then stopped. The charge warning light was off. As I was 120 miles from home and driving from a hotel to a vendor's and had no tools with me, I thought that I would wait 'til I got home.
I drove 10 miles, parked up for the day and then set off for home. I got less than 10 miles, only for every warning light on the dash to illuminate and the power-steering to stop working. Luckily I was close enough to an emergency layby to get off the road.
It turned out to be simply a lack of drive to the alternator. The belt drives a pulley, which drives a shaft, which drives the alternator via a clutch. The clutch had failed, so the alternator was turning, but slipping badly. That must have generated enough to prevent the light coming on, but nowhere near enough to keep the battery charged (the car keeps the glow-plugs powered for emissions purposes and uses a 1kW electric heater to speed up warming the engine from cold).
SteveW
Yes the same belt. The battery light came on when ignition was switched on along with the engine management light and both extinguished when the engine started.
If I had been traveling on a motorway I would not have notice3d anything amiss as the steering was the o9nly warning. On this engine (common with ford fiesta) the water pump is driven off the cam belt so the engine doesn't overheat .
As it has happened with two different vehicles now I suspect the battery symbol is sensed off of battery voltage rather than whether the alternator voltage has exceeded battery voltage which is all the old ignition warning light used to do.
AJH
Are you sure it wasn't the rev counter, on diesels the alternator is (was) often the only convenient feed to run a rev counter from.
I had an alternator fail on a 2000 Alfa 156 diesel. Until the battery died the only evidence anything was wrong was that the speedometer didn't work.
Old battery warning light fed the rotor field coil a limited current to get it started. That produced a magnetic field which produced output from the stator at idle speed. A separate rectifier fed some of that to the voltage regulator which then fed the rotor field coil. When field coil voltage rises it reduces the current flow though the bulb, so it goes out.
No, it really was the speedo, because I remember trying to work out my speed from the rev counter.
It's a common rail diesel and it gets the revs from the ECU. Speed is worked out as an average of the individual wheel speeds via the ABS/stability control computer.
Series 1 Landy? :-)
I was thinking Commer van, the one with the front wheels inset.
And where the same dash is fitted to a range of cars some lights don't come on because the feature is not fitted to that model.
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