Rev counter !

[knight]

Popped out for a blast last night, drove to a petrol station about 15 mins away, a few mins after leaving I noticed the rev counter was not working and the dash lights seemed dimmer, the car also seemed to be juddering slightly, pulled off at the next junction and the engine died as I was slowing down, fortunately made it to a layby where we tried to jump start it, but had no luck so called the AA out to get me home. This morning I removed the battery and gave it a good charge and it started fine but the revcounter was still not working. Changed the big fuse and the rev counter was still not working. I was thinking of getting a new holder and trying that but is there anything else it could be? Will also change the battery for a nice heavy duty one soon.

[Brian March]

Sounds a lot like your alternator has failed. The battery is trying its best to power everything but just isnt getting recharged by the alternator. I've had this in the past - driving along, watching the gauges fail one by one until eventually the engine gave out too

[brakedust]

get a volt meter on your battery with the engine running and you should see about 13.5v if you dont then your alternator is probably off, is the battery light on in the dash?

[knight]

Don't remember seeing the battery light on. I'll pop to the garage and check the battery voltage.

[knight]

11.9 volts with the engine running. Had the battery charging yesterday for at least 4 hours so I'd thought that would have given me a decent charge. Does this sound definately like the alternator?

[jjones]

yes, most likely cause. you should be seeing over 13v

[Nicholas Blair]

I'd double check the Big Fuse connections, even replace it again.

Edited by Nicholas Blair on Monday 16th February 13:36

[optimax sniffer]

To confirm if the big fuse is at fault, I guess that you could connect the two cables together temporarily to see if the fault goes away.

But I think that it is the alternator

[HarryW]

optimax sniffer said:

To confirm if the big fuse is at fault, I guess that you could connect the two cables together temporarily to see if the fault goes away................

Agree with this, don't junk the Alternator until you have done this as a resistive fuse would give you a voltage drop too.

[HarryW]

Also remove the fuse, run the engine and pick up the +Ve (big red wire that goes to the fuse holder) on the back of the alternator to measure the output directly with no load.

[knight]

Cheers guys, got a few things to check tomorrow

[VPower]

knight said:

11.9 volts with the engine running. Had the battery charging yesterday for at least 4 hours so I'd thought that would have given me a decent charge. Does this sound definately like the alternator?

A good battery should give you 12.4 volts at least.
If it is left below 12.4 volts the battery will be damaged eventually.

[RUSSELLM]

You need 10-20% more than the voltage of the battery to charge it.

So in the case of a 12V battery, Between 13.2 & 14.4 volts to charge.

As mentioned above, if you suspect the fuse. Put the Red lead of your multimeter on the alternator side of the fuse & test it there. If it's still below 13.2 V with a few revs, then it'll confirm your Alternator's duff.

[Toadusmodus]

And remember the Cerb alt does not provide enough at idle, only around 12v and sometimes less with an electrical load on. Needs about 1500rpm to show whether its pumping out enough juice (as already said 13V +)

[knight]

Toadusmodus said:

And remember the Cerb alt does not provide enough at idle, only around 12v and sometimes less with an electrical load on. Needs about 1500rpm to show whether its pumping out enough juice (as already said 13V +)

Yep am aware of that, will be checking it on my own so I have got my 3 hands ready to take the reading!!

[RUSSELLM]

It ain't necessarily so o o o, it ain't necessarily so o

Just been out with mine relocating the ECU & mines producing 14.14 on tick over.

That said, it's ticking over at almost 1200RPM

Must get that sorted

[knight]

Wouldn't start earlier so its now on charge before I can check the voltage! Think I might bite the bullet and get a new battery as this one seem to be suffering!

As an aside, how easy a job is it to remove/refit the alternator? I have an early 4.2 with A/C, and was planning on getting the alt overhauled by an auto electrician.

[knight]

One of these days I'll manage to check the voltage!! Got the car started only for it to die about 30 secs later and then refuse to restart!! Gonna get the battery tested by a mate this evening.

[Gazzab]

Would be suprised if it is your alternator.
Is big fuse properly seated?
Do you need to improve an earthing?

[knight]

Have tried a new fuse and it was the same. I have ordered a new holder to see if that could be causing a problem.

Not sure how to go about checking the earth! Any tips as to what I should be looking for?