Battery

[Guest firenzaman]

Very recently my pug 205 gti as some how got slower at starting (well actually its just the sound of the starter motor) It still starts but just turns over slower and I have lost confidence and expect it to let me down soon. It sometimes clicks whilst turning over like when the battery is getting very flat. I have had a new battery and alternator in the last 6 months. I used my multimeter across the battery terminals and got 13v at rest which went upto over 14v when the engine was running. Once the engine was stopped the battery went down to 13v but kept going down by.01v every 20 secs is this normal ? Have I got a problem and if so what with. I removed the main HT lead and span the engine over on the starter without it firing and it span quite freeley and with speed so I don't think it's the starter motor.

[ablister 31]

sounds like you have a battery drain somewhere in the cars' electric system. If you connect your multimeter in series on the battery and set it to amps then watch the readings. If you remove fuses to each circuit in turn, you'll know roughly where the drain is coming from as the amps will drop when the fuse is removed.

[jim21070 2]

From your description I'm assuming it is always slow to crank however soon after it has been stopped. This does not immediately suggest a slow drain problem. The battery could be the problem but it's really quite new so I doubt it.

 

Sounds more like either an earthing problem or bad connections to me. It could be the starter motor itself. Do check the connections from the battery to the starter solenoid, both positive and earth, especially the earth where it connects to the gearbox. These connections are often corroded. Also, the positive battery connector has the cable crimped in as standard and this often corrodes badly over the years and fails. This corrosion can be internal and not immediately seen. A new connector is the answer.

 

What you see with the battery voltage is pretty normal. It will fall down in small steps when off charge and will often sit around 12.5V even though theroy says it should be higher. You have proved the alternator is putting out the right charging voltage. The acid test is to put a meter across the battery when cranking and then across the starter solenoid. It should not drop below about 10 - 11V. If you see a marked duifference in measuing across the battery to that seen across the starter itself, you have a large voltage drop occurring between the battery and motor that indicates a high resistance between the two. Another good test is to see by how much the headlamps dim when cranking. If they really dim down badly, this again suggests bad connections or a starter motor that is really badly worn; a really worn starter will take a great deal more current than one in good condition.

[Guest firenzaman]

From your description I'm assuming it is always slow to crank however soon after it has been stopped. This does not immediately suggest a slow drain problem. The battery could be the problem but it's really quite new so I doubt it.

 

Sounds more like either an earthing problem or bad connections to me. It could be the starter motor itself. Do check the connections from the battery to the starter solenoid, both positive and earth, especially the earth where it connects to the gearbox. These connections are often corroded. Also, the positive battery connector has the cable crimped in as standard and this often corrodes badly over the years and fails. This corrosion can be internal and not immediately seen. A new connector is the answer.

 

What you see with the battery voltage is pretty normal. It will fall down in small steps when off charge and will often sit around 12.5V even though theroy says it should be higher. You have proved the alternator is putting out the right charging voltage. The acid test is to put a meter across the battery when cranking and then across the starter solenoid. It should not drop below about 10 - 11V. If you see a marked duifference in measuing across the battery to that seen across the starter itself, you have a large voltage drop occurring between the battery and motor that indicates a high resistance between the two. Another good test is to see by how much the headlamps dim when cranking. If they really dim down badly, this again suggests bad connections or a starter motor that is really badly worn; a really worn starter will take a great deal more current than one in good condition.

Thanks for all that didnot realise that a worn starter motor would take more current than a new one so if your starters on the way out it will put strain on battery and charging system eventually. I will do all the above checks luckily I bought a newly refurbed starter of ebay a while ago when I had alternator/battery probs. So this hindsight may come in handy for once. Only paid a tenner and its here in my garage so aint got to go and fetch one.