Vauxhall. New battery and altenator fitted but battery still goes flat. Why?

Question

My vauxhall battery discharges in about 2 weeks. I had a reconditioned altenator and a new battery fitted, (and a new cambelt). It worked fine for a while, but now the battery goes flat 2 weeks or so after I recharge it. Any advice would be greatly appreciated. Thanks.

The car is diesel.

The car starts OK for a week or two, then the battery goes flat again.

Answer 1

Something must be draining the battery - it's mostly likely to be either and aftermarket alarm or stereo system, but could be just about anything in the car. you need to take it to a mechanic who specialises in electronics I'm afraid (or try un-installing your stereo or having your alarm looked at by who ever fitted it)

Answer 2

I'm a little unclear on how it is you know the Alternator is good, but lets assume it is. It's really not that hard to find a drain. The required tool is pretty cheap and the basic techniques are actually pretty simple, although it can be a little time consuming. Most cars have some items that take a little electricity while the car is turned off. But not enough to drain the battery unless it sits for a long time. You will need to buy a 12 volt test light. You can find these at any Auto parts store for about $5-$10. Start by dis-connecting the Battery Negative cable, and connect the test light between the cable end and the battery post. It should light because of those items that are always on. Remove the fuses for those items, usually the Radio, (the clock and station memory) the ECM, BCM and, Alarm, etc., if so equipped. Make sure you know where to put the fuses back in when you're done. Then start to remove the other fuses. When the light goes out, you have found the circuit that your drain is coming from. That will narrow it down quite a bit. There are usually multiple things on the same circuit, so you may have to unplug some individual items to find the particular thing. A wiring diagram helps here, to know what's on that circuit. Ask at the library for a book with these. Once you find the offending circuit, just put that fuse back in, and start unplugging things on that circuit, until it goes out again. That's your drain. One time I found that it was the cigarette lighter receptacle had a bunch of crud in it, so that it was as if it was always on!

Answer 3

Confirm you are saying the car is left idle for two weeks, i.e. not started? If this is the case its probably down to a permanent load like the immobiliser (may be expected, depending on the draw).
If the car runs for 2 weeks and the battery goes flat then its because its not charging. You mention the cam-belt (not relevant to this) but is the fan-belt okay (very relevant).... Do you have a battery warning light on? I assume the voltage regulator was replaced with the alternator?
If the car was running off the battery it probably wouldn't run for 2 hours never mind 2 weeks so you need to find out why the battery isn't charging. Could be wiring, poor connection, regulator (unlikely), fuse, relay or the battery itself. I suspect, without seeing the car, that you have a blown in-line fuse or failed relay. Engine fuses and relays are under the bonnet. The fuse/relay box lid normally identifies what each fuse/relay is for, have a look.

Answer 4

You can easily measure the "parasitic" current draw in amperes that your car uses when it's parked. After it has been parked for an hour or so, simply touch the test leads of a Digital Multi-Meter (DMM available at Sears, $15) between one disconnected battery cable and the battery terminal it was disconnected from. The DMM should be set to the 10 ampere scale. Make sure all the courtesy lights and other auxiliary electrical are turned off in the car. The DMM should read less than 1/4 ampere (250 milliamperes). If not, begin removing and replacing each fuse until you find the fuse circuit that's causing the excessive parasitic current draw from the battery. Then locate the problem connection in that circuit.

Answer 5

There must be a discharge. What I mean by that is something in the car is drawing battery power when the car is switched off. Take it back to whoever fitted alternator,hopefully he is an auto electrician,and ask him to check how much draw is on battery when car is switched off. The clock ifyou have one always draws a very small amount which wont account for battery going flat.Check yourself that all the interior lights switch off when closing doors,including the boot and under bonnet if one is fitted

Answer 6

I had a Vectra that went flat in 2 weeks if it wasn't being used. The immobiliser/alarm took quite a high current. I used to disconnect the battery if I wasn't planning on using the car for some time. The downside to this was that I had to re-code the radio every time and reset the clock.

Answer 7

try taking it somewhere to be tested. with the car running and the battery hooked up your alternater should be pushing around 14 to 15 volts. if its less than that you may have gotten a bad alternator. but since its staying charged for 2 weeks you may have a problem somewhere else - like a slow voltage leak - if you have an aftermarket stereo - check all the wires and make sure its hooked up right. driving also plays a factor here - if your not driving it regularly, batteries tend to lose charge especially in cold weather.

Answer 8

There is obviously a drain on the battery but finding it is not always that easy

First place to look at is the boot or tailgate interior lamp. They have been known to remain on and when closed you can't see it

Failing that I think you might be taking it in for a check

Good luck

Answer 9

get an auto electrition to check output from altenator and peform discharge test on battery if all ok use clip on ampmeter on battery lead to confirm drain on battery them locate fault (yes new parts can be faulty it happens all the time) is battery correct hd type for diesel?

Answer 10

make sure battery leads are connected proper to their terminals if so try a new altenator also try running car with no heaters on to give battery full charge but sounds to me like its the altenator.good luck.