Suspected alternator issue

[Shude]

After my car was rear-ended a couple of months ago I've had an intermittent "battery" warning light appear on the instrument cluster. I initially suspected that the battery was damaged somehow but it's not shown signs of any problem.

The warning light has usually lit up for about 20 seconds at the start of the journey and not come back. It's done that pretty much every day for the last few of weeks, I've not worried about it.

Now it's decided to come on only when doing sustained speeds of around 70-80mph (indicated). My journey to work is about 1/3 (time) motorway so this means that my battery isn't being charged for 1/3 of a journey (that *is* what the warning light means, right?).

It didn't do it today for some reason, at all!

Someone suggested that a belt could be slipping or something but I wouldn't know where to start looking in the engine bay to even find the stupid alternator, let alone visually inspect it for any kind of damage or wear.

Anyone got any clever ideas?

P.S. I'm open to the suggestion that it's temperature-related, I just realised that today was one of the warmest days we've had for a while and my car was rear-ended the week before the first session of frosty-mornings. Maybe the motorway speeds cool something down at the front of the car enough to stop something gripping or change the properties of something?

 

[Satch]

Take a look at this.

http://www.starteralternator.com/alternator_troubleshooting_check.htm

 

[Shude]

Take a look at this.

http://www.starteralternator.com/alternator_troubleshooting_check.htm

Hmm, looks interesting.

The issue with mine is intermittent though, which is why I think it's a bit odd!

Perform ALL of the following tests with the ENGINE RUNNING at 2000 RPM with LIGHTS AND HEATER FAN ON

I can just about manage the heater fan thing these days

measure from the ALTERNATOR CASE to the NEGATIVE BATTERY POST. A reading HIGHER THAN 0.25 VOLTS INDICATES A PROBLEM with the negative battery cable or connections to frame/chassis and engine block.

Isn't that going to require a *long* multimeter cable?

I will see if I can get someone to help me with these tests at the weekend...

 

[guydewdney]

Quote:
measure from the ALTERNATOR CASE to the NEGATIVE BATTERY POST. A reading HIGHER THAN 0.25 VOLTS INDICATES A PROBLEM with the negative battery cable or connections to frame/chassis and engine block.


Isn't that going to require a *long* multimeter cable?

I will see if I can get someone to help me with these tests at the weekend...





you could do the test in two parts - alternator to chassis / engine block. then negative of battery to chassis. if the first is poor then its the alternator to engine block / engine block to chassis earthing strap (quite common on vauxhalls) - the second would indicate battery terminal loose / bad cable to chassis / loose bolt to chassis....

hth

 

[Shude]

you could do the test in two parts - alternator to chassis / engine block. then negative of battery to chassis. if the first is poor then its the alternator to engine block / engine block to chassis earthing strap (quite common on vauxhalls) - the second would indicate battery terminal loose / bad cable to chassis / loose bolt to chassis...

I think the problem only happens at sustained high rpm though, difficult to test stuff at 70mph on the motorway, this is why I was hoping that someone would be able to say "oh yes it's *something* that's not working!" etc . Otherwise everything is working perfectly, so the tests will most likely come back with no problems.

Like I said I will try some stuff out at the weekend, Sunday probably.

 

[Brian WH]

If it only happens at high speed, then my money would be on a loose or slipping belt drive mate.

 

[Dieselman]

If the fault is only present when travelling and not when stationary then suspect the wiring loom as it moves when the engine is under load and when there is air flow.
Also check the connections on the alternator itself.

ps. the alternator is the round electrical generator looking thing mounted on the side of the engine near the front, with the main belt driving it.

 

[Msmax]

Have had similar problems with my E290TD.

The alternator has the regulator mounted (with 2 philips type screws) at the back, just under a black plastic cover fastened with 3 screws.
The regulator has also the brushes mounted to it which makes contact with the rotor windings. In my case the brushes and/or the spring pressure to the rotor contacts were not good enough to make proper connection. The brushes were also too short.

So, I changed this regulator (including the brushes off course) and the
problem is gone. Regulator for my alternator was about 40 euro.

Also check if both nuts for the wires are thightened firmly at the back of the alternator.

Hope this will be helpfull.

Msmax

 

[Shude]

The alternator has the regulator mounted (with 2 philips type screws) at the back, just under a black plastic cover fastened with 3 screws.
The regulator has also the brushes mounted to it which makes contact with the rotor windings. In my case the brushes and/or the spring pressure to the rotor contacts were not good enough to make proper connection. The brushes were also too short.

This sounds very interesting! I am beginning to seriously HATE electric motors! I will take a look at the catalogue to see if I have these items you mention and where they are/part numbers/prices etc.

Thanks!

 

[Msmax]

Hi Shude,

Have a look at the attachment which I have send to your Yahoo account.

Msmax

 

[Shude]

Have a look at the attachment which I have send to your Yahoo account.

please don't send anything to that, it's "inactive"! The best address to use for me is [email protected]

 

[glojo]

Hi Shude,
If I remember things correctly, didn't this problem first come to light after the 'hit and run'?

Forgive my ignorance, but if the answer is yes, then where is the battery located on your vehicle?

I cannot think why this would effect the warning light coming on when the engine is working quite hard but it must(might) be a symptom. It certainly sounds more like a charging type problem...

But I just wonder if the impact damage caused some sort of electrical problem which perhaps highlights itself at certain wind type pressures on the bodywork? (speeds of 70mph)

My suggestion may be silly but at least someone with a better understanding of your specific model might just consider it, then dismiss it.

Fingers crossed that you solve the problem,
Good luck,
John

 

[Webby]

Shude,just had a thought.There's a terminal block in the boot just ahead/behind the battery, I was having trouble at one time and I discovered that one of the "heavy" cable terminals was loose.Removed the terminal, cleaned the contact and re-tightened,success.Maybe the bump has disturbed the wiring at that point.

 

[Shude]

I just realised that I never posted the results!

I took the car for a service and mentioned the problem, they inspected the car, the problem went away and I paid £18 for diagnostics and "no fault found". It hasn't come back though and it's been nearly a year

Thanks for your help everyone