Battery Light permanently on

[darbon]

Evening peeps.

Got in the car this evening after finishing work, started it up and noticed that the battery light was still on and stayed on for the 38 mile \ 1.5 hour drive home.

Got my DVM out across the battery and was reading 11.9v. Started the engine and it dropped to 11.5v. Put lights, blowers, etc on and got my lad to rev the engine and it dropped to 11.2v and no increase in voltage, as I believe its supposed to be around the 13 to 14v mark??

Question is, do I change the alternator belt (looks a bit shiny but tension and grooves seem ok) or do I go the whole hog and change the alternator? Or am I barking up the wrong tree??

Any suggestions gratefully received!!

Dave

[mickeydunne]

Could just be belt slip.

[petrol-head16v]

Yes you are right mate it should be around 13.2v - 14.5v give and take when running first check to see if your belt is on and turning the alternator if o.k then I would defo go for a new alternator as its not charging the battery, check to see if it drops below 10v when staring (may need two people to check this) if so your battery may need replacing aswell.

[darbon]

Did a check against my lads car (ZR 160) and on his was showing 12.4v off load and 14.1v with engine running and lights on!! Belt on mine is turning the alternator and tension seems fine. Both belts are shiny looking on the outside so I'm convinced its the alternator that's packed up.

Petrol-head -- it does not drop below 11v either on or off load, but not 100% sure about battery as voltage seems to be dropping very slowly off load (i.e when first checked it was reading 11.9v but was dropping and after running the engine for a 5 minutes then switching off, it had dropped to 11.4v.

Next question is what type of alternator will I need to replace it with as there seems to be variations - 65A, 85A. I have an 05 Trophy Se 105.

[petrol-head16v]

Did a check against my lads car (ZR 160) and on his was showing 12.4v off load and 14.1v with engine running and lights on!! Belt on mine is turning the alternator and tension seems fine. Both belts are shiny looking on the outside so I'm convinced its the alternator that's packed up.

Next question is what type of alternator will I need to replace it with as there seems to be variations - 65A, 85A. I have an 05 Trophy Se 105.

There may be a sticker on it saying the amps check this first as some ZR's are different

[Longerz]

defo alternator then do you have air con if so u need the 85amp

[Baldrick56]

I was incredibly lucky with this, had the same issue where light came on, stayed on a while then usually extinguished after driving a bit. Investigated - belt was nice & tight but battery terminals (both) were loose (& I mean flappingly loose). Tightened both & (touch wood) hasn't happened since. Car was in at the Auto-Electricians just over a month ago for electric window motor replacement, I suspect the guy didn't tighten them (at least more than finger tight) then.
Regards, Rob

[Baldrick56]

Update: No I wasn't incredibly lucky The day after I wrote the previous post, I have the same problem with my ZR160. After I fixed the terminals the light went out - for about two days. I reasoned that arcing across the loose terminals had probably done for the rectifier in the Alternator so I ordered a new one. It took two weeks to get here & last weekend I spent most of the day fitting it (there was an issue with the connector which I'll post separately about).
Result is the light's still coming on! (it did go out briefly but soon re-lit itself). Cannot believe there's the same fault in two alternators - where else do I look?
Incidentally with the original alternator & after the light came on my stepson discovered that the car would keep running if you pulled a battery terminal off - with a voltmeter there was about 0.2V more from the Alternator than the battery on its own.
Regards,
Rob