Ford Focus battery warning light
Variant: 1.8 TDDI Ghia Diesel
Model Year: 1999
Categories:
Running Rough, Starting & Power Loss
When I start the engine the battery warning light goes off temporarily and then comes back on. I measured the alternator output voltage at the battery and read 16.5V which according to the haynes manual is too high and tells you to change the voltage regulator. This seemed to make sense because I am able sometimes to get the battery light to go off by turning on my lights and heated windscreens which presumably brings the voltage down. I wasn't able to get hold of a new regulator so I replaced the whole alternator, the voltage is now correct but the fault light is still there and I can't get my windscreen heating to turn on. I've had a look at the wiring while I was replacing it and couldn't find anything obviously wrong. I've had it suggested to me that the high voltage could have cooked the battery but if that were so I would have thought I would have trouble starting the car, I'm not sure but I wouldn't have thought an unserviceable battery would be able to bring the battery warning light on with the engine running.
Could anyone either explain to me how the battery can be responsible, or give me an idea what else it might be.
Could anyone either explain to me how the battery can be responsible, or give me an idea what else it might be.
Posted: Dec 13, 2011 (13 years ago)
If the heater motor is your problem , it could be the heater resistor .
"Focus battery light problem .
This is the correct test method for the alternator on this car.
Check the condition of the alternator 3-pin connector and surrounding alternator regulator area. If there is any damage, replace the alternator and/or the wiring loom.
5. Commence the charging system diagnostics program. If the alternator fails with an indictment code then replace it and re-test the system. If the alternator fails without an indictment code, go to the next step.
7. Voltage comparison test with 3-pin connector connected.
- Switch on dipped headlights and heated rear window, and run the engine at idle.
- Watch for 20 secs then record the voltage output across the battery terminals.
- If the output is not between 12.5 and 15.5 V, and /or is unsteady (ie. varies by +/- 0.2V) replace the alternator and re-test the charging system.
- Switch off the headlights, heated rear window and engine, and proceed to the next step if the output is steady and within range.
8. Make sure the ignition is off, then disconnect the alternator 3-pin connector and be certain that it is held in a safe position.
- Run the engine at idle, switch on the dipped headlights and heated rear window.
- Check that the output is steady by observing for 20 secs, then record the voltage output across the battery terminals. Switch the engine off.
- If this output is the same as the one from the previous test then the alternator is running in default mode and needs to be replaced. Re-test the charging system.
- Go to the next step if the output is different.
9.Ignition off load test. Re-connect the 3-pin connector, with the ignition off.
- Measure the vehicle key off current load between the battery ground cable and the battery negative terminal using an ammeter.
- The alternator is ok if the current is below 2 Amps.
- If not, disconnect the alternator battery positive connection and re-measure the vehicle key off load.
- If the current dips below 2 Amps, replace the alternator and re-test the charging system.
You can buy the wiring harness from a dealer. Then you can see what you have to do. Bad/broken wiring is a very common problem on these. Follow the wiring from the 3 wire plug on the alternator back and usually about 8" - 12" there is a broken wire. Uncover the plastic covering to inspect it. "
"Focus battery light problem .
This is the correct test method for the alternator on this car.
Check the condition of the alternator 3-pin connector and surrounding alternator regulator area. If there is any damage, replace the alternator and/or the wiring loom.
5. Commence the charging system diagnostics program. If the alternator fails with an indictment code then replace it and re-test the system. If the alternator fails without an indictment code, go to the next step.
7. Voltage comparison test with 3-pin connector connected.
- Switch on dipped headlights and heated rear window, and run the engine at idle.
- Watch for 20 secs then record the voltage output across the battery terminals.
- If the output is not between 12.5 and 15.5 V, and /or is unsteady (ie. varies by +/- 0.2V) replace the alternator and re-test the charging system.
- Switch off the headlights, heated rear window and engine, and proceed to the next step if the output is steady and within range.
8. Make sure the ignition is off, then disconnect the alternator 3-pin connector and be certain that it is held in a safe position.
- Run the engine at idle, switch on the dipped headlights and heated rear window.
- Check that the output is steady by observing for 20 secs, then record the voltage output across the battery terminals. Switch the engine off.
- If this output is the same as the one from the previous test then the alternator is running in default mode and needs to be replaced. Re-test the charging system.
- Go to the next step if the output is different.
9.Ignition off load test. Re-connect the 3-pin connector, with the ignition off.
- Measure the vehicle key off current load between the battery ground cable and the battery negative terminal using an ammeter.
- The alternator is ok if the current is below 2 Amps.
- If not, disconnect the alternator battery positive connection and re-measure the vehicle key off load.
- If the current dips below 2 Amps, replace the alternator and re-test the charging system.
You can buy the wiring harness from a dealer. Then you can see what you have to do. Bad/broken wiring is a very common problem on these. Follow the wiring from the 3 wire plug on the alternator back and usually about 8" - 12" there is a broken wire. Uncover the plastic covering to inspect it. "
Posted Dec 13, 2011 (13 years ago)
Have you had a look at this similar problem:
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Posted Aug 22, 2012 (12 years ago)
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