Hi there,

 

Had a problem with a flat battery the other day, jumped it and then got Hicas & ABS lights flashing. So decided to charge battery up fully and after charging, it was reading a little over 12 volts, put in the Z and then car started fine, did a test once engine started and volts where showing at 14.42, but after revving the car it showed no volt increase and after a couple of minutes running, the volts were slowly decreasing.

 

Is the Alternator faulty which it sounds like?

 

Cheers

Alternatively, the battery might not be able to hold charge, either or.

does sound like it , another test to do ,

visual ,,is to turn on main lights and rev engine if no increase in brightness would also show your alternator not charging ,

 

,check all earth conections as well, and conections to alternator , its worth a clean up and a look , could save you a few pounds,

I dont have a battery tester, any other way of finding if battery is faulty, apart from taking it back to Halfords who I got it from, its still under warrranty with about a year and a half left on it?

I dont have a battery tester, any other way of finding if battery is faulty, apart from taking it back to Halfords who I got it from, its still under warrranty with about a year and a half left on it?

 

If you dont use the car as a daily driver you could charge it, leave it sitting for a week then re check, a bit crude i know but would give you an idea.

may be im wrong , but if it increased to 14.4 , with engine running that is correct ,

 

i would suspect the battery , a dont see why halfords wouldnt help you im positive most batterys now days come with 2 yr warranty

yep, if your alternator was knacked, you wouldnt see 14.4 volts. sounds like the battery is on its way out. A 12v battery should be around 12.5 volts ( if not a bit more) anyway as the idea is that they should drop to 12v under load.

Cheers guys, I will probably take the battery back to Halfords and get them to test it, as you said, it wouldn't increase to 14.4 volts if the Alternator was faulty.

also make sure you got the correct battery as these cars take an awful lot to crank over from cold and if not used for a long run wont recharge the battery properly ideally 15/20 miles driving to keep charge topped up more at night if lights used HTH

Well I got the battery tested at Halfords and its fine, in fact turns out that the Alternator is pumping out too much power, and this is why my ABS & HICAS lights are still coming on, so looks like I gotta replace it.

One for sale here http://www.300zx.co.uk/forums/showthread.php?t=63632

 

But why would your volts decrease if the alternator was pumping out to much power.

*****cks to halfrauds, alternators either work or they dont. Usually the brushes wear out, meaning you wont get your 14.v volts, (which you are), or a diode dies in the bridge rectifier meaning you dont get 14.4 volts ( which you are).

 

14.4 volts is not too much power. With the batter disconnected what voltage are you getting, ideally it should be over 12 volts.

 

This may be stupid but have you checked your fluid levels?

Well first the guy at Halfords told me that the battery was fine and was giving out 12.9 volts when disconnected and said that it wasn't dropping power. When I told him that it was giving out 14.42 volts when engine running and then slowly dropping after a few minutes, he said that the alternator was at fault because it should hold a steady charge all the time and not drop.

 

I cant check the fluid levels because its a sealed battery and I cant get the top off without forcing it, but not sure what this would do to it.

 

I put the battery back on, started the car up but the Hicas & ABS lights are still coming on, and the car jumps when you drive it, so I quickly turned around and parked it back up again.

when the alternator is charging it should charge above 12v.

mine when charging reaches 14.5 volts so sounds like alternator is fine

You said you tested the battery yourself and only got just over 12v, the guy at halfords is claiming nearly 13, sounds like he doesnt want to give you a new battery.

 

You said that when the car was running your voltage was 14.4 volts but this slowly dropped off, what did it drop off to?

Yeah my battery test before running it on the car was 12.42 volts, when running the engine it went to 14.42 volts and then every 30 seconds or so, was dropping down to 14.32, 14.22 etc etc, to which point after a few minutes I turned it off.

hmm 12.4 doesnt sound too bad in all honesty , like i said a decent battery should be around 12.5, so .1v is niether here nor there so you battery may indeed be ok. I wouldnt worry about the slight drop off in volts either, from what youd said i thought it was dropping off rigth down to 12 volts or something quite quickly.

Hmm strage one, get someone on here to check their for you and see if the voltage drops off, if it doesnt then i dont really know, maybe the voltage regulator in the alternator is duff, but i would have thought if it was then you would either be getting either no volts or maybe crazy volts, ie over 15.

 

have you searched for info on flashing abs lights, is there an error code for this?

Don't believe these high street "specialists" - I took my battery to one to be tested and they said it was fine. But having got similar symptoms as you I took it to a proper auto electrician who confirmed that the battery was indeed fooked. (still had short term voltage capacity but little current capacity)

Are you able to "borrow" a battery to confirm?? Or put yours in another car??

Whether the battery or alternator is causing the problem, I believe the battery is not 100%. It feels light on water and the indicator which should be green is now dark as in nothing showing. Halfords said that it needs topping up but the level is ok though and only worry if it goes white, so maybe there is a temporary problem with the battery I dont know, its just so weird.

 

My other car is the wife's nissan sunny 1.4, but I dont know what my battery would do as its more powerful.

 

I'll have to ask around and borrow another battery from one of my mates I think to make sure.

Just a quick update and to thank everybody for their help, the problem turned out to be an earthing issue, so thankfully nothing major just annoying, but thanks to everyone for their advice though.