Hi all, the latest entertaining little problem from the A2 is this:
- barely enough charge in battery to start the car from cold, a couple of very short journeys leave it completely drained
- sluggish turning over, sometimes fails to start first/second time
- EML comes and goes, VCDS-Lite returns this
17588 - Linear O2 Sensor; Pump Current: Short to Plus
P1180 - 35-10 - - - Intermittent
(clearly this is a secondary symptom though, caused by voltage dipping during cranking)
- FM radio reception poor when rear screen heater is ON
This last one made me think it's the main earth point for the starter motor behind passenger headlight, as it was one of the gremlins that went away after cleaning this earth point up a couple of years ago. I repeated the procedure but that wasn't it.
Some more info:
- the battery is only a couple of years old but was a cheap brand (Platin)
- after charging the battery with a mains charger (charging voltage is 14.1V), the engine cranks vigorously and starts first time, everything is back to normal for a couple of days
- with the engine running, alternator output is 14.26V wrt battery -VE terminal, but at battery +VE terminals I measure 14.05V (expect these should be the same?)
- voltage drop between alternator +VE terminal and battery +VE terminal (engine running) is 0.11V (measured at another time from above)
- voltage between starter motor earth point and battery -VE terminal (engine running) is 0.005V
- I have ruled out the battery fuse at +VE terminal, just a few mV is dropped across this
- In ny wife's Mazda, the voltage at alternator and at battery is the same at 14.5V. The battery in the Mazda is a stop-start type though.
Is it normal to drop 0.1-0.2V between alternator +VE and battery +VE terminal, can anyone comment? Am I looking at a poor connection somewhere between the alternator and the battery, or is it more likely the battery is shot, or the alternator needs seeing to? The alternator was replaced 4 years ago with some after-market type, not OEM type.
- barely enough charge in battery to start the car from cold, a couple of very short journeys leave it completely drained
- sluggish turning over, sometimes fails to start first/second time
- EML comes and goes, VCDS-Lite returns this
17588 - Linear O2 Sensor; Pump Current: Short to Plus
P1180 - 35-10 - - - Intermittent
(clearly this is a secondary symptom though, caused by voltage dipping during cranking)
- FM radio reception poor when rear screen heater is ON
This last one made me think it's the main earth point for the starter motor behind passenger headlight, as it was one of the gremlins that went away after cleaning this earth point up a couple of years ago. I repeated the procedure but that wasn't it.
Some more info:
- the battery is only a couple of years old but was a cheap brand (Platin)
- after charging the battery with a mains charger (charging voltage is 14.1V), the engine cranks vigorously and starts first time, everything is back to normal for a couple of days
- with the engine running, alternator output is 14.26V wrt battery -VE terminal, but at battery +VE terminals I measure 14.05V (expect these should be the same?)
- voltage drop between alternator +VE terminal and battery +VE terminal (engine running) is 0.11V (measured at another time from above)
- voltage between starter motor earth point and battery -VE terminal (engine running) is 0.005V
- I have ruled out the battery fuse at +VE terminal, just a few mV is dropped across this
- In ny wife's Mazda, the voltage at alternator and at battery is the same at 14.5V. The battery in the Mazda is a stop-start type though.
Is it normal to drop 0.1-0.2V between alternator +VE and battery +VE terminal, can anyone comment? Am I looking at a poor connection somewhere between the alternator and the battery, or is it more likely the battery is shot, or the alternator needs seeing to? The alternator was replaced 4 years ago with some after-market type, not OEM type.