Sorting a bad battery to engine earth
As your car gets older then we are all likely to suffer from earth problems and particularly the main battery earth as it's very exposed to the weather.
Symptoms might be the car starter turning slower than normal (just like I had) for no real reason. This is where many just dash out and buy a new battery but hold it! Do some checks first, there may be nothing wrong with your battery
VOLTAGE DROP TEST
This is a very quick and simple to do test. With the engine running so it's under normal conditions and feeling the effect of any vibrations, simply check the voltage between the negative battery terminal and a good shiny metal earth on the engine.
Here's the setup and this is showing a good result of 0.02v
Mine was showing over 0.24v to start with and that's not good. This means the alternator is getting a false idea of the battery voltage and the battery will never get a full charge
Ok so we're after the earth point, disconnect the battery of course
and I needed to disconnect the air filter supply tube to gain access.
Here's the battery to engine earth on a 1.6
Ok so after cleaning up the contact points and reconnecting the earth to the engine I decided to check the resistance between the earth lead and an engine earth (note battery earth lead still disconnected here and multimeter is set to measure resistance) and that looked good at 001 ohms
After reconnecting the battery and with the engine running, multimeter set to measure voltage, our voltage drop test now shows we're down to 0.02v, that's more like it
So we now have the strong sounding starter we always had before, battery voltage is restored to normal and it's all cost us nothing. Those are the kind of repairs I like
As your car gets older then we are all likely to suffer from earth problems and particularly the main battery earth as it's very exposed to the weather.
Symptoms might be the car starter turning slower than normal (just like I had) for no real reason. This is where many just dash out and buy a new battery but hold it! Do some checks first, there may be nothing wrong with your battery
VOLTAGE DROP TEST
This is a very quick and simple to do test. With the engine running so it's under normal conditions and feeling the effect of any vibrations, simply check the voltage between the negative battery terminal and a good shiny metal earth on the engine.
Here's the setup and this is showing a good result of 0.02v
Mine was showing over 0.24v to start with and that's not good. This means the alternator is getting a false idea of the battery voltage and the battery will never get a full charge
Ok so we're after the earth point, disconnect the battery of course
and I needed to disconnect the air filter supply tube to gain access.
Here's the battery to engine earth on a 1.6
Ok so after cleaning up the contact points and reconnecting the earth to the engine I decided to check the resistance between the earth lead and an engine earth (note battery earth lead still disconnected here and multimeter is set to measure resistance) and that looked good at 001 ohms
After reconnecting the battery and with the engine running, multimeter set to measure voltage, our voltage drop test now shows we're down to 0.02v, that's more like it
So we now have the strong sounding starter we always had before, battery voltage is restored to normal and it's all cost us nothing. Those are the kind of repairs I like
