Save an alternator? It's fine, problem was + cables high ohm

Xaccers · Unread post by **Xaccers** » 22 Aug 2011, 12:39

Cassy is fitted with a refurbed alternator, it must be about 4 years old now, and quite often the battery light glows dimly, the voltage at the battery on tick over is about 13V
Thing is, sometimes the battery light isn't visible at all.
Like last night, started her up, battery light was glowing, turned headlights on and it didn't make much difference.
On the way home the light wasn't visible, so during the journey the voltage had risen enough.

It's had LHM drip on it from a leaky pump while I tried to find the souce (was the bell end seal) so that's not helped.
She starts fine, so the battery is getting charged, I do quite high mileage throuh work mostly on dual carriageways.

So, what's likely to be up, and can it be repaired or should I plan for a replacement?
How exactly does LHM damage it?

Unread post by **myglaren** » 22 Aug 2011, 13:29

I imagine the first thing the LHM does is to soak into the brushes and gum them up and coat everything in a somewhat resistive layer of gunk that accumulates dust and becomes greasy mud.

I expect a bit of dismantling, a few doses of electrical cleaning spray and a set of new brushes would cure it.

DickieG · Unread post by **DickieG** » 22 Aug 2011, 15:10

Bearing in mind you've had problems causing the light to illuminate, the dash bulb may be blackened causing it to look dim when illuminated. The easiest way to test the alternator is to connect up a voltmeter across the battery and observe the reading which should be around 14v or more with the engine turning over at say 2,000 rpm, then load the alternator with headlights/HRW/heater fan etc where the voltage should still remain around 14v. The cause of the dash light staying on could be due to a poor earth somewhere.

Unread post by **Peter.N.** » 22 Aug 2011, 15:43

The dim glow is cause by the exciter terminal on the alternator being lower in voltage that the battery which possibly suggests that the regulator is faulty. You can buy them quite cheaply from ebay and they are not difficult to fit, certainly cheaper than a new alternator.

Maybe one of these from ebay

Peter

Xaccers · Unread post by **Xaccers** » 22 Aug 2011, 16:06

Richard, battery light comes on fully bright with the ignition first turned on so not blackened, when it's glowing it will brighten in time with the indicators and with the use of the brakes.
Across the battery it's the lower end of 13V@2Krpm, could indeed be a dodgy earth.

So, could be:

1. Dodgy earth/feed
2. Regulator (although the voltage is quite stable, just low)
3. LHM gunk on the bushes

DickieG · Unread post by **DickieG** » 22 Aug 2011, 16:17

The easy way to check for dodgy earths between the alternator, engine, body and battery is to use decent jump leads as a bridge across each item to the negative battery terminal whilst observing a voltmeter.

SaabC5 · Unread post by **SaabC5** » 22 Aug 2011, 16:30

If you need to go the recon route i can recommend this firm

http://www.westlancsautoelectrics.com/

I've used them several times for starters & alternators, their prices include return postage of the old unit and the units they ship out look like new.

citronut · Unread post by **citronut** » 22 Aug 2011, 18:55

i have seen dim glowing charge lamp caused by corosion between the regulator mounting and the body of the alternator,

also the only prob with sticking a new regulator on is if the slip rings have grooves worn in them, the new brush's with the new regulator will not sit corectly/fully against the slip rings,

regards malcolm

Unread post by **xantia_v6** » 22 Aug 2011, 20:04

If your alternator has had LHM through it, you should really wash it out (at least around the brush-gear) with something that dissolves LHM.

Your warning light glow could be caused by high resistance in the cable between the alternator and the battery. You could run the engine from cold for a minute or so, and feel if the connection at the alternator or battery terminal are significantly warm, if so, you have found your problem.

Xaccers · Unread post by **Xaccers** » 22 Aug 2011, 20:24

xantia_v6 wrote:If your alternator has had LHM through it, you should really wash it out (at least around the brush-gear) with something that dissolves LHM.

Your warning light glow could be caused by high resistance in the cable between the alternator and the battery. You could run the engine from cold for a minute or so, and feel if the connection at the alternator or battery terminal are significantly warm, if so, you have found your problem.

Excellent idea!

Xaccers · Unread post by **Xaccers** » 23 Sep 2011, 17:56

The ends of the double cable from the positive terminal were covered in verdi gris, and the positive terminal was rather hot.
Trimmed the ends off and refitted them to the terminal, no more glowing battery light and headlights are even brighter.
Haven't had a chance to actually test the voltage.

So, what can I coat the cable ends in that will protect them from the elements but still conduct electricity?

Unread post by **myglaren** » 23 Sep 2011, 18:28

Vaseline.

Xaccers · Unread post by **Xaccers** » 23 Sep 2011, 20:16

myglaren wrote:Vaseline.

Excellent, Danielle's just said that as Cassy's a girl she can have some of Danielle's pink vaseline...

citronut · Unread post by **citronut** » 24 Sep 2011, 07:45

or you could fabricate a citro blood deflecter from an ice cream tube, to place between the alt and H/P pump, mind you eat the ice cream first, and it has to be a decent cornish variaty

,

also if your clever you could make it so it not only protects the altanator, but collects the citro blood and returns it to the tank

regards malcolm

Unread post by **CitroJim** » 24 Sep 2011, 08:15

Xac wrote:
myglaren wrote:Vaseline.
Excellent, Danielle's just said that as Cassy's a girl she can have some of Danielle's pink vaseline...

I had to make do with Strawberry flavoured lip balm the other day....

Not as good as the pukka stuff