17 replies to this topic

[MuppetDonkey]

So I've started looking into why my battery is constantly going flat, tested the alternator (at the battery end) and it was running at 15.8V at idle. 

 

From this I am working on the following assumptions:

 

1: I need a new regulator for the alternator

2: My lovely new battery is probably fried as I took it out for a GOOD run this week.

3: I'm quite lucky it wasn't a lot worse

 

I have two questions: 

 

- is it worth trying to source and replace the regulator or is it a new alternator job? If the former does anyone have any pointers? there's some kak on ebay that I don't really trust, but I can't really find anything in the normal places.

 

- is the battery salvageable? It has only had one run, but it was quite a long one

 

It's a '99 Cooper with 65A alternator.

 

Thanks

:)

[smurfomatic]

Had a similar problem a couple of years back, relatively new alternator (bought because the old one had a broken mounting) cooked the battery. Fortunately the battery was still under a 5 year warranty - so carried it the half mile or so to Halfords, got a replacement, re-fitted the old alternator and got going again! 

 

I would personally suggest a new alternator and certainly would check the battery and expect to replace that too.

[Spider]

I would also suggest checking all the Earths.

[johnR]

There was a company selling alternator re-furb kits on Ebay - Gold Lion auto electrics. A complete kit for £15, bearings, rectifier, brushes etc. great company to deal with and much cheaper than replacing the entire unit. 

[MuppetDonkey]

Annoyingly this was my suspicion.  just a bit of wishful thinking I guess :)

 

 

Had a similar problem a couple of years back, relatively new alternator (bought because the old one had a broken mounting) cooked the battery. Fortunately the battery was still under a 5 year warranty - so carried it the half mile or so to Halfords, got a replacement, re-fitted the old alternator and got going again! 

 

I would personally suggest a new alternator and certainly would check the battery and expect to replace that too.

[panky]

Just did a quick search, stupid cheap

 

https://www.ebay.co....3.c100033.m2042

 

I've just changed the alternator on my Commer camper, might try one of these to re-furb the old knackered on.

[MuppetDonkey]

Thanks  - this is what I was originally intending to do today - it's just finished a major resto with a mix of new and used parts, so I thought a few bad earths could be the issue as the battery was charging but would only turn over a couple of times before crapping out.

 

I was just testing the alternator as a formality, didn't for a minute think it would be the problem.

 

It's my own fault for taxing it this month!!! :)

 

I would also suggest checking all the Earths.

[monkey]

I had this problem a few weeks back, voltage was all over the place from 11.6 up to 15.9v, I first noticed when driving at night the lights went SUPER bright lol, anyway for speed I brought this...
https://rover.ebay.c...tm/292773240532

Super quick delivery and it’s working a treat, kept the only one to refurb at my leisure

[tiger99]

I strongly recommend checking the calibration of your voltmeter before jumping to any conclusions about the alternator. There was a case on the forum several years ago where the meter being used was probably well out. It is rather common with the cheap, nasty stuff (and some stuff that pretends to be of good quality, and is priced accordingly) that floods the market nowadays.

 

I have found that a brand new Duracell (not applicable to any other brand) AA battery measures 1.65V at 20 deg C. A stack of 10 in series (stick them in a suitable tube) should measure 16.5V if your meter is ok.

[Aroutin]

Control your plus cable connections for oxidation.
What wil also cause an higher charging voltage.

[KernowCooper]

Just to add a point the excess voltage would start to boil off the electrolite and when this get lower than the plates then thats where the damage is done not directly by voltage alone, so sort out the alternator. if your batteries one of the newer sealed type your snookered, if you have access to the cells then have a look at the level. Some sealed batteries have a press in cover you can remove for a look

[MuppetDonkey]

So after checking everything I can think of, I found a few questionable connections but my main fault seems to have been quite a rare one ......

 

..... a faulty multimeter!!

 

Out of curiosity I tested the other cars, apparently either both had the exact same fault or my multimeter was over reading.  Borrowed my Dad's and you could see the difference.  So I've bought a maintenance charger (which I should have bought anyway) and am letting it charge slowly, that seems to have sorted it - it's able to start multiple times at least.  When its had a few days on charge, I'm going to leave it off charge for a couple of days then see if it starts, just to be sure.

[phillrulz]

So after checking everything I can think of, I found a few questionable connections but my main fault seems to have been quite a rare one ......

 

..... a faulty multimeter!!

 

Out of curiosity I tested the other cars, apparently either both had the exact same fault or my multimeter was over reading.  Borrowed my Dad's and you could see the difference.  So I've bought a maintenance charger (which I should have bought anyway) and am letting it charge slowly, that seems to have sorted it - it's able to start multiple times at least.  When its had a few days on charge, I'm going to leave it off charge for a couple of days then see if it starts, just to be sure.

 

Thats why in industry a multimeter isnt a legally or health and safety approved instrument to check for dead. We have to use a set voltage indicators. 

[KernowCooper]

One of the reasons why I did this post here "Recommend me a multimeter"    http://www.theminifo...e-a-multimeter/

[monkey]

One of the reasons why I did this post here "Recommend me a multimeter" http://www.theminifo...e-a-multimeter/

Sorry to hijack but...
Do you still recommend the same one? The leads on my cheap multimeter need replacing and I don’t know wether to buy new leads or replace the whole tester