alternator changed but battery light still coming on??????

**vectrani** · 23rd June 2018, 12:24

Well guys I'm looking for some help. The vectra decided last month that it was gonna throw the battery light on so long story short I have changed the alternator and battery for a new one. Tho the battery I had to change I only put in at xmas. The mechanic said the battery wasn't holding charge. So I took it down to the motor factors I bought it off (manager is a friend of mine )and they basically done a reset on it and phoned me 2 days later and said the battery is fine. Any way I have been driving the car for the last 3-4 weeks with the new battery and alternator and on monday the battery light came back on!!. I got home and turned the car off and the light went out and stayed out until my commute home on tuesday afternoon. Again I got home and the light stayed off until yesterday afternoon . So I went back to see my mechanic and we put it on his dignostic machine and it said the alternator is doing its job it is charging and the battery has nice bright green light on it. I know the car has a fault in the aircon somewhere and the dpf temp sensor has burnt out as well buy we are scratching our heads to wonder why it keeps throwing the battery light on?? When the light came on yesterday I drove around 12 or more miles in stop start traffic and the car wasn't showing any signs of stopping? The only theroy I have thought about is if the crankshaft pulley is on its way out (no noise from what I can hear)would it be causing the belt to slip intermittently (when I horse the car on) and bringing on the battery light?? Any help is much appreciated guys.

**Woody** · 23rd June 2018, 13:33

Take it to Halfords and get a free independant battery / alternator check done.

**vectrani** · 23rd June 2018, 16:11

Originally Posted by Woody

Take it to Halfords and get a free independant battery / alternator check done.

The battery and alternator where checked and are running 100% so I'm just sitting scratching my head I have ordered a new crankshaft pulley ao will fit it when it arrives

**northpole** · 23rd June 2018, 17:14

Clean the big 3 grounding points on the main ground cable and clean the UEM with am electrical cleaner.... 9 out of 10 times it should be enough to sort out ground problems something that usually shows up like that.

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**Critch** · 23rd June 2018, 18:28

Has your mechanic physically tested battery?

That green light isn’t worth **** in measure that one battery cell.

tested alternator under load?

**vectrani** · 23rd June 2018, 19:10

Originally Posted by Critch

Has your mechanic physically tested battery?

That green light isn’t worth **** in measure that one battery cell.

tested alternator under load?

Yeah he physical cheked it and we used the dignostics on a run in the car and it showed it was charging. I have read in an old post about aftermarket alternators not agreeing with the vectra and it was flagging up faults. I've been out and about in the car today and the light kept coming on buy car still running 100%

**rufuel** · 27th June 2018, 01:33

Any luck yet? I have a kind of similar problem. My alternator light works every morning when I start the engine. It goes on and off as it should be. But that is only time during the day when it works. When I go shopping or what ever, it just stays on even the engine is running. It charges and the voltage is ~14.2, but the alternator light doesn't shut down.

Does someone know how the alternator light works at Vectra c (z22yh)? How does it know when to shut down?

**justin32** · 27th June 2018, 02:26

ive had 5 alternators in 6 years on my Vectra.

**Big Dave** · 27th June 2018, 10:55

Originally Posted by justin32

ive had 5 alternators in 6 years on my Vectra.

Blimey!! My old Vectra was still on the original one at 8 yrs old and 106,000 miles when the car got written off.

**NickT** · 27th June 2018, 11:42

Load test the battery, not physically look at it. A bad cell can still have charge and the alternator part charge it to a point. I've never seen a 'reset' on a battery ffs.

Old school me would put a voltmeter on AC and see if there is any voltage. This would give an indication of a bad dose in the alternator on the 3 phase. This would appear to give a DC charge but not correctly.

If the battery is a traditional wet cell lead acid type I'd use a carbon pile load tester, not a plug in type that just applied a reverse current to get an indication of sulphination of the plates in a cell.

Another thing to note, just because something is new, doesn't mean to say it works. ...