new battery-crap start

[Doctor Foster]

Have new good quality battery fitted on van for about 3 months. If I dont use the van for a couple of days and then try to start it struggles to turn over but will then will fire up. First impressions are the battery is flat but its not. This Happens quite often. If I drive the van round the black then try restarting it fires up no problems. Have checked the voltage and all seems ok.

Any ideas??

[CovKid]

First port of call, the starter motor connections. Do you have a stereo thats using battery power to maintain its memory?

[Doctor Foster]

First port of call, the starter motor connections. Do you have a stereo thats using battery power to maintain its memory?

Yes. Stereo is connected to unswitched supply

[Red Westie]

Areas to look at: Battery earth and positive lead connections to the gearbox and starter motor. The solenoid switch wire connection.
If the starter motor is the unsupported type then then bush in the gearbox may have worn oval.
The brushes in the starter motor maybe worn low.
Ignition switch fault...but less likely.

Martin

[Doctor Foster]

Forgot to mention that If I charge the battery up its starts perfectly but once left for a few days, thats when it starts to struggle

[ghost123uk]

Sounds like summat is draining it - as mentioned, modern stereos often do this ( as on our Scirocco )

Do you have a multimeter ?
If so do you know how to safely use it to measure current (amps) ?
(I ask because if you are not sure, you can damage you meter)

If the answer = "Yes", then take off the positive battery lead (engine NOT running of course and ign OFF) put the leads on the heavy red wire and the battery terminal, (red lead to terminal, black to the heavy battery lead) and measure what current reading you get - it should be less that 200mA ideally, even with the radio fully connected (but "off")

If you are not sure about any of the above, best post back and ask for more info as "guessing" is not a good idea when dealing with car batteries !!

With the meter still connected, disconnect the radio and see what it drops to.

If that does not have much effect, go round pulling the fuses, one at a time, until you come across one that causes the current reading to fall noticeably, you have then gone a long way to isolating what is causing the drain.

DO NOT try to start the engine without reconnecting the main battery lead back to the battery (that will blow the meter for sure !!)

If there wasn't much in the way of drain showing, it may be that the battery is faulty and not holding a charge - the supplier should be able to test it (and replace under g/tee if it is faulty)

[Doctor Foster]

I do have a multimeter so will do some checks when I get chance.

Have just been through some receipts and remember that this battery was a warranty replacement for the last one which had problems. Im thinking that maybe something caused the first one to pack up and is now buggering up this one!!

[Doctor Foster]

Had a look at various wiring in the van and discovered the stereo was wired up incorrectly. I have found the user manual and now rewired it as per instructions with one live connected to an unswitched 12v supply and the other connected to a igntion switched 12v supply. (before both stereo wires were connected in the same terminal which was unswitched)

Have also rewired fag lighter and dashboard fan to 12v ignition switched supply

Battery no back on charge so I hope thats cured it.

[Doctor Foster]

Nope still no joy. How long does a battery take to charge?? I gave it a couple of hours but the stable voltage of the battery is 11.5v

12.3 volts when engine ticking over

[Oldiebut goodie]

Both those figures are too low. Charged battery at rest should be around 12.7v, engine running 14+v.
Is your multimeter good?

[Doctor Foster]

Both those figures are too low. Charged battery at rest should be around 12.7v, engine running 14+v.
Is your multimeter good?

Yeah its a fairly decent one. I have put battery back on charge again. Will have another look at readings later tonight.

Any other ideas??

[ghost123uk]

Any other ideas??

Yes, first put your meter onto a modern car and see what readings you get :-

A = Engine off ( As said above, should be close to 12.7 Volts )
B = Engine running ( As said above, should be around 14 Volts )

That way you will be checking your meter is reading right and finding out what readings you should get.

Charge the battery on a home charger (where the reading should be around 14 Volts when the charger is on) - turn charger off and disconnect - leave battery standing for a few hours and measure the voltage - if it is below 12.5 then the battery has had it.

Also sounds like you have either a dodgy meter or a dodgy charging circuit on the van, in view of the low readings you get with the engine running.

[Doctor Foster]

Hmm getting 13.5v when engine running now so I guess thats normal. Gonna see what the battery is reading in the morning

[Doctor Foster]

Ok I checked the readings with my meter this morning. On first turn of the key the starting voltage dropped to 10.5v???

Van fired up and charging voltage was 13.5v so seems that the alternator is doing its job.

Let the van run and turned radio and lights on, the voltage dropped to 12.5v with engine ticking over. voltage rose up to 13. 4v with engine being revved

Could the starter motor be zapping the battery???

[CovKid]

Ok, sounds exactly like the problem I had. Modern stereos seem to demand more power than you think (sometimes ridiculous amounts), even when apparently switched off and it sounds like the unswitched side is the culprit. Mine too would be flat in three days so assuming you have a second or leisure, put the whole thing on the leisure, that way you won't ever have a flat starter and the leisure will soon catch up. I simply have two starter batteries and anything likely to drain starter goes on leisure (or second battery). If you don't have a second battery, its easy enough to add one and all I can say is that it completely solved my problem and why I came up with the voltage meter mod.

Relevant sections are here:

https://club8090.co.uk/wiki/Ca ... it_charger" onclick="window.open(this.href);return false;
https://club8090.co.uk/wiki/VW ... ging_cause" onclick="window.open(this.href);return false;

Good luck. Be very surprised if this didn't solve your problem.

As a footnote, I actually dropped the unswitched that supplies stereo preset memory. That may not suit you, but I never listen to the radio and can live with flicking through tracks if I have to. Cost (including second battery if you get the £55 Exide battery from Euro Car Parts) shouldn't be much more than £70 if you're frugal and hunt for parts, and you'll find it useful anyway as you can sit with stereo on for a couple of hours without having to be pushed or towed.