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· Registered
6 Posts
Discussion Starter · #1 ·
Hi there People

I have an October 97 Passat 1.8 20v Turbo which I absolutely love.
I am the second owner from new.
A new battery was purchased prior to me buying the car in July 2009

The charging light always goes out straight away and never re-illuminates till the vehicle engine is switched off, even when stationary, and on tick-over the light is not on.

It started off that the battery for some unknown reason began to lose its charge over a short period of time.
I initially thought that it was discharging itself through a various piece of equipment, i.e. heated rear screen etc. etc.
I have checked that all the relevant accessory switches are turned off but it still continues; now here is the problem.
Sometimes I can get in the car two or three days later and it starts straight away, other times it is a matter of two days and it struggles to start.

I feel that this is an intermittent fault, so I have only posed three scenarios
So my questions are as follows;

1.Do I replace the battery ?

a).I don’t really want to do this in case I sell the car.

2.Do I further investigate where this drain is originating from?

b).I am more than capable of tracing a drain to source.

3.Do I purchase a “heavy duty jump starter ?

c).Then if feasible I could take it with me.

· Registered
5,252 Posts
Well, an auto parts store can test your battery for free. It's not perfect, but it should help.

If we assume the battery is good, then you have a parasitic drain. Hook the battery into an ammeter with the ignition off, and assuming you do see a decent drain, start pulling fuses until it stops and work from there.

Until you get this fixed you should probably keep a jump box in the car, but it's not substitute for fixing the issue. Neither the alternator nor battery are really designed for repeated deep-discharge. It'll kill even a good battery relatively quickly (they make deep-cycle batteries, but those aren't used with cars), and it's pretty stressful for the alternator. At the least, you should probably pry the caps off your battery and top off the fluid with distilled water. (Even "maintenance free" batteries can sometimes benefit from maintenance like this.)

· Registered
5,908 Posts
This topic comes up fairly frequently, and causes usually come down to: (a) is the alternator really providing the appropriate charge voltage, or (b) is the battery capacity marginal, or (c) is something drawing current from the battery that shouldn't be. For (a), naturally use a DWM. For (b) use sirwired's suggestion of a battery load test. For (c), use a low-wattage, say 2W or less, 12V light bulb inserted between the battery (-) post and ground cable clamp or battery (+) post and positive cable clamp. Assuming the bulb lights up due to a real parasitic drain, this method has the advantage of not needing to close enough to read numbers on a meter.
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