Alternator

[Ethos 0]

Ok,

 

Since when the car was hot it was stalling alot, i've got a trusty multimeter and done some testing...

 

When the car is off; 12.63

When the car has turned on; 14.37

 

Now... when I left the car running for about 20 minutes the voltage slowly got less and less until it got to 13.30 when it started dipping from 13.30 to 12.80 and eventually stalled.

 

So, alternator is fried yes?

 

Steve has given me two to try so I might do the same test when I fit another one so I don't flatten the battery!!

 

Just want to check before I change it over (never changed one before).

[large 33]

I don't think the voltage should drop off after 20 min. Are there things comming on like the engine fan?

[Ethos 0]

I don't think the voltage should drop off after 20 min. Are there things comming on like the engine fan?

 

Sorry, I completly forgot to put... I turned it on- checked the voltage then turned everything electrical on. Lights, heater, back light, fog light.... I'm pretty sure the fan didn't start.

[large 33]

So the car was running with every thing turned on and the volt meter was on 12.8v.

[Ethos 0]

So the car was running with every thing turned on and the volt meter was on 12.8v.

 

It kept dropping until it got to 13.30, then the revs dopped (went to do 12.8volts) then would rise to 13.30 again, then to 12.8v. The revs were climbing then dropping all the way to stalling

[Roman 0]

hello

i hawe some prob in the past and you must check two thing's first(diode plate)one or more diode is i short cut this is hard to measure in it because you get false reading.prob No2 is

brushes(but rare) not drop voltage. if you see headlight blinking when you drive 20-30 min

then sure failure in diode plate

[Ethos 0]

hello

i hawe some prob in the past and you must check two thing's first(diode plate)one or more diode is i short cut this is hard to measure in it because you get false reading.prob No2 is

brushes(but rare) not drop voltage. if you see headlight blinking when you drive 20-30 min

then sure failure in diode plate

 

Can anyone explain this a bit more, sorry I don't quite understand

 

I haven't noticed the headlight blinking at 20-30 minutes but engine goes to stall when at idle after this time.

[Roman 0]

ok i try but my english is bit rusty... you must took apart alternator. diode plate is first thing

you see plastic cap on side you must remove and desolder 3 vire and unscrew 4 bolt

easyest fix is buy new diode plate i thin its not problem to get is valeo part

[Roman 0]

oh and voltage on good altenator is betwen 13.8V 14.6V measured with new diode plate

(this is what i read on my alternator)

[KRISKARRERA 2 1 Cars]

But what is the problem here? The engine's stalling right, so how did you get to thinking it was alternator causing this?

[saveloy 8]

It certainly sounds like an alternator issue. Battery voltage is OK. So it sounds like something within the unit is breaking down.

 

But what is the problem here? The engine's stalling right, so how did you get to thinking it was alternator causing this?

 

Given the revelatory guise of another of your posts, do you think Scarlett would appreciate other types of mechanical devices?

[KRISKARRERA 2 1 Cars]

Well apparently she does have a few toys . Not that she needs them.

 

I'd certainly like to know what's up with my alternator. Switch on the indicators and you can see the headlights dim as they flash on and off. And it's supposed to be 70 amp.

[Ethos 0]

But what is the problem here? The engine's stalling right, so how did you get to thinking it was alternator causing this?

 

Because over 20 mins the voltage dropped over 1 volt, and when it did the engine started struggling? To me that's pretty much perfect evidence?!!!!!

[Ethos 0]

Because over 20 mins the voltage dropped over 1 volt, and when it did the engine started struggling? To me that's pretty much perfect evidence?!!!!!

 

Ok, well i've changed the alternator.... same thing The other alternator might not be 100% but it's doing exactly the same thing.

 

Back to the drawing board.

 

Maybe a bad earth somewhere or something?

 

It's when I turn on the light and the heaters or anything else.

 

What a pain!

 

...on a plus side I changed the alternator without much trouble! Pretty chuffed with that

[ablister 31]

have you checked the cable from alternator to battery + terminal. Check the readings by connecting your meter to output connection on alternator then checking reading at battery +, should be no more than 0.5v difference between readings.

 

Could also be battery too, not holding charge?

[Ethos 0]

have you checked the cable from alternator to battery + terminal. Check the readings by connecting your meter to output connection on alternator then checking reading at battery +, should be no more than 0.5v difference between readings.

 

Could also be battery too, not holding charge?

 

Good thinking actually, I haven't tried reading the V straight from the alternator. Will give that a go tomorrow. The earth cable is very thin, is that normal? I had to recrimp it too...

 

It's a brand new battery and measures 12.6v when the car is off, so should be ok. This is the last "running" problem the car has. So if I can get it sussed I'm going to be chuffed!!

 

Then again, even if the cable is a bit dodgy wouldn't it show up before turning everything on?

Edited November 24, 2007 by Ethos

[saveloy 8]

Here is a suggestion. And this applies to you too Kris. Connect a jump lead from battery negative to body. And then re-check the voltages. Kris, see if you get the flickering then. That will rule out an earth problem.

[KRISKARRERA 2 1 Cars]

To body? The body has paint on it though so it'd hardly gonna be a good conductor. Where else can I use?

[flipperthebushkangaroo 2]

a couple of questions for you,

1. do you get battery light on when engine starts to cut out, or for that matter at all even when ignition first switched on?

2. is the battery actually fully discharging.

 

if diode pack(voltage regulator) is failing expect the battery to fully discharge.

 

if battery warning comes on when ignition on but not as engine fails unlikley to be alternator.(mine ran until battery was fully discharged only missfiring in last couple of seconds)

 

if battery light does not come on at all most likley broken exciter wire (doubles as warning light circuit) it goes through brown mulit plug above gearbox.

 

hope this helps narrow down problem at least

good luck

Roddie

[ablister 31]

To body? The body has paint on it though so it'd hardly gonna be a good conductor. Where else can I use?

 

earth from alternator casing to bettery - connection.

 

Or earth battery - connection to something that is bolted to body eg suspension struts, main earth points, brake m/c etc

[saveloy 8]

earth from alternator casing to bettery - connection.

 

Or earth battery - connection to something that is bolted to body eg suspension struts, main earth points, brake m/c etc

 

Kris, re you so fick as to think I meant you needed to bolt a jump lead to some paint?

You dumb arse. Connect the OTHER end to the suspension turret stud. You know, like bare metal.

[KRISKARRERA 2 1 Cars]

Yeah and I'll kick your arse so hard you'll have to unbutton your collar to s*it

[saveloy 8]

Whilst you are doing that, I will:

diagnose your problem,

attempt a repair,

test said repair,

if it does not work, re-step my actions and ascertain the correct course of action,

make you a cup of tea,

repair your car with time to spare.

And, you'll thank me for it.

 

P.S: thanks for the Scarlett pics, they're grand.

[dani959 0]

You should sort your stalling problem first. If your mixture isn't right you won't get your car to idle properly, it will jump around 500-1500 RPM, and at 500 revs your alternator is not really charging!

 

If it doesn't idle, your alternator voltage obviously starts dropping (not enough revs).

[Rob_the_Sparky 9]

Because over 20 mins the voltage dropped over 1 volt, and when it did the engine started struggling? To me that's pretty much perfect evidence?!!!!!

 

No, that could be meaingless, the alternator power output drops with revs. Below a certain point it can no longer generate enough power to maintain the voltage and it will drop off. Sounds to me like the revs are dropping to a point where the alternator can no longer maintain the voltage. Oh and the rad fan switching in and out can easily stall a car if the idle is already a bit suspect and will certainly drop volts (due to increased power demand). 20 minutes of engine running stationary sounds like enough to bring the fans on. This will increase the load on the engine (via the alternator) hence will reduce the idle speed.

 

Rob

 

P.S. You can also run the engine without the alternator belt. Would tell you if struggling idle is a function of the alternator but that could be due to electrical load rather than a duff alternator.