Alternator/battery

[Guest Andy Mack]

Hi,

 

Well my car broke down yestarday. The AA man says its the alternator and the battery is goosed. BUT i got a jump start and drove home fine. Then when i got home i turned the car off and then back on to see if it would start and it fired up fine. The AA man said that the battery was gone, and the alternator wasnt charging at a normal rate, it was fluctuating.

 

Also it seemed to work after bashing it with something, and then not work if you bashed it again. Could it be some loose connection from the alternator that is cutting off all the electricity to the car?

 

Also it did this 1 time before but seemed to fix it self and i drive home fine. But when it does it there is a funny clicking sound(like click click click click really fast and constant) but once the battery is working or whatever is wrong with it, the clicking stops. What could that be?

 

Thanks

 

Andy Mack

[Anthony 1,003]

The AA and RAC have a bit of a reputation for trying to sell people batteries when they aren't really needed (if you believe the scaremongering TV programs anyway), so just because he said the batteries knackered doesn't mean it is. Plus I'd personally be suprised if both the battery *and* alternator were knackered.

 

Also, when you say it works/doesn't work when you hit it - what are you hitting, and does the engine cut out and not start? A faulty alternator will just not charge the battery - if the battery still has enough juice to turn the starter over then it will still have enough juice to run the engine electronics/ignition.

 

The easiest way to check if the alternator is working is to check the voltage across the battery terminals with the engine running - should be ~14.5 volts. Also, the battery warning light on the dash should come on if the alternator's kaputt.

[RichF 1 2 Cars]

Although not really the answer to your question, there was a program on TV a while ago (Watchdog perhaps) that did a feature on breakdown companies trying to scam customers particularly by trying to sell them batteries.

 

You can check the alternator yourself as per the Haynes manual, something like this (from memory) :

 

1. Put a voltmeter across the battery and start the car

2. Bring the revs up until the voltmeter shows a constant value, somewhere around 12/13 volts.

3. Whilst keeping the engine at constant revs switch on loads of electrical stuff, e.g. lights, rear demister, heater blower etc. The volts across the battery should remain constant.

Edited January 23, 2004 by RichF

[Guest Andy Mack]

he hooked it up and the voltage across the batter was fluctuating from 13~to sometimes 14. never 14.5 though.

 

I was bashing the alternator and it worked.

 

It just seems strange that i could be driving and then the thing dies, but when i can drive home and it will start fine when im at the house. Could it just be an intermitten fault of the alternator telling me its about the die?

 

Edit - He didnt actually try to sell me one, he just said it was knackered. Although he did say he was ment to.

Edited January 23, 2004 by Andy Mack

[Guest Andy Mack]

1. Put a voltmeter across the battery and start the car

2. Bring the revs up until the voltmeter shows a constant value, somewhere around 12/13 volts.

3. Whilst keeping the engine at constant revs switch on loads of electrical stuff, e.g. lights, rear demister, heater blower etc. The volts across the battery should remain constant.

Ok i started it up and measure the volts. It fluxuated from 12 to 13 and 14. It didnt really remain constant.

 

So then i turned on the lights, fan and heated rear window. Then it sat at a constant 14.50.

 

Does that mean the alternator is fine?

 

If it does would it just be a faulty connection between the battery and alternator? Or could it be that its telling me its on the way out?

 

Cheers

 

Andy Mack

[RichF 1 2 Cars]

You need to really get the volts reading constant before you start upping the electrical load, otherwise seeing a fluctuation is difficult.

 

Did you keep the revs constant and keep them constant throughout the test ? (I don't mean at tickover speed, something like 2500 rpm)

 

(You either need an assistant or a brick on the accelerator etc.)

Edited January 23, 2004 by RichF

[Guest steveo]

I agree with the others that you shoudl not believe the AA or RAC about the battery/alternator as they all have quotas/targets that they have to meet on selling these items.

 

Here is what you should do. Get a volt meter, start the car and switch the headlights on, the volts reading should be at a steady 14v to 14.5v. Try this again and add in the heater blowing on full......the volts should be steady again. The volts reading you are getting with the lights off is correct and all is ok.

 

My advise is don't start bashing the alternator as the RAC/AA bloke advised. This will nacker it up.

 

You could check ouy the wire and remove any corrosion on the connectors as well.

[Guest sillypugger]

looks like your regulator is knackered mate, which means a new alternator.

 

your voltage should sit higher (if not the same) with nothing switched on and when you apply load (switch stuff on) the voltage will drop a bit but should go back up when you increase the engine revs to about 2000rpm.

 

if it falls below 13.5V AT ANY TIME (except with engine not running) your alternator is knackered.

 

you should also get a stable reading.

 

it is pretty common for the battery and alternator to be knackered at the same time. the alternator goes first and due to not being charged up properly (or not at all) the battery then dies. if the battery isn't pretty new then the plates can buckle if it's totally discharged (generally car will just 'conk-out' while driving) and the battery can't be charged anymore.

 

also the battery doesn't supply the car with electricity - the alternator does.

the battery is there purely for starting the car and the alternator charges the battery back up while driving. if your alternator isn't working THEN the battery will be supplying the car and this is why it gets discharged.

[Guest steveo]

Sillypugger, it is NOT common for the battery and alternator to be knackered at the same time, I have NEVER had this nor know of anyone who has.

 

However you are correct in saying that if the alternator dies then the battery will supply the power, then drain, then the car will stop.

 

You will NOT kill the battery, warp the plates etc or what ever you like to call it and you WILL be able to charge it. Just take out the battery and charge it over night or till its full. ONLY if a cell dies will the charge not hold.

Edited January 23, 2004 by steveo

[Guest Andy Mack]

Ok so looks like the Alternator is actually knackered then?

 

I did the test with the car at idle speed(no assistant or brick to be found). So i dont know if it would remain constant if it was at higher revs.

 

But when i turned on the electrics why would it then remain constant(again at idle speed) if it was knackered? Wouldnt it just drop the more load i put it under?

[Guest steveo]

Andy mate, you only are testing the battery voltage with the engine running, lights on dipped and blower on full. If it a contstant voltage then the charge from the alternator is ok. I spent hours on this one till my I eventually spoke to my mate who is a mechanic (and a god on electrics) and he explained it all to me, then showed me.

[Guest Andy Mack]

good cause i was out in my car today for about 45 mins and it seemed to work without any problems.

 

Hopefully it will get me to work tonight without going mad again.

[Guest steveo]

Just check & clean up those wire connectors (removing any corrosion) onto the alternator. Apart from that its will be ok.

[Guest sillypugger]

Sillypugger, it is NOT common for the battery and alternator to be knackered at the same time, I have NEVER had this nor know of anyone who has.   

 

I work in Halfords and see this at least a couple of times a week. Just because you or anyone you know hasn't heard of this doesn't mean that it can't/doesn't happen. This is especially bad in winter which - surprise surprise - is the season we happen to be in.

 

You will NOT kill the battery, warp the plates etc or what ever you like to call it and you WILL be able to charge it.  Just take out the battery and charge it over night or till its full.  ONLY if a cell dies will the charge not hold.

 

You don't know much about batteries do you? What do you think a dead cell is?

 

It is amazing (and sad) at the amount of breakdown 'engineers' who diagnose a flat battery as the cause of a breakdown when actually the alternator has caused the battery to get flat (just because it is classed as a fix and they get out of the rain/wind/snow). Running your car with a dicky alternator WILL kill your battery.

 

Only batteries that have calcium or certain types of silver technology will not buckle the plates. Unless your car is brand new within the last couple of years or you have had your battery replaced with one of these types then it probably has one of the types that can buckle.

[Guest steveo]

Don't know anything!!!! Yeh right. You don't even know what I do for a living buddy. You are the one who works in Halfords which means eff all. Bet you don't even get your hands dirty fixing the engines anyway.

 

Let's not start a slagging match anyway.

 

New battery is different to 'the last couple of years' but I do agree with your comment about getting the latest type. Good point.

[Guest sillypugger]

You are the one who works in Halfords which means eff all.

 

It means i see stuff that you don't even know exists.

 

Bet you don't even get your hands dirty fixing the engines anyway. 

 

Well don't go into Ladbrokes cos you'll be destitute in no time.

 

I don't need to know what you do for a living cos your post at 4:20pm says it all.

 

Finished.

[pug_ham 244 3 Cars]

IMO they can fail at the same time but it is the alternator that causes this to happen.

 

I've had a battery & alternator die at the same time, the battery & alternator were on the car when I bought it, I was leaving work & the car wouldn't even turn over the battery was so low, figured the battery had died through old age so I 'borrowed' one from one of the work cars to get me home.

 

Got home fine with lights etc on but when I came to go to work the following morning I had the same problem so I phoned in to take the day off to sort it. I charged the battery up for a few hours & it worked OK for me to take the car & get it tested.

 

The battery failed the test first & the alternator was charging but not high enough so when driving with the lights etc on the battery was still being drained.

 

Luckily I had an alternator so I swapped that & bought a new battery which fixed the problem.

 

When I went to work & next saw the car I had 'borrowed' the battery from, my old one was still fitted so maybe I picked the wrong car to swap batteries from or the alternator killed it. Although it did need a new battery a few weeks later iirc.

 

Graham.