Grrr...car just broke down.

[krede]

well.. my murena Is back on the road agan... though with the old alternator still in place..
I took the battery to work, and put tha tester on it, and it turned out to be fine.
i installed it and took a reading at the battery poles with the engine ideling high (with the choke on) and it said 14.2 volts... witch i presume is fine.
But the ampmeter in the dash still just barely rises above minimum when the circuit is unstrained.. as soon as the heater and the headlamps are switched on the needle drops to the "minus" part of the gauge, and the chargelamp flickers slightly..
God forbid i ever turn on the radiatorfan!!..
So... I know what I am doing tomorrow  .... however I seriously doubt that i will manage to get under the car by just jacking it up and using axlestands 

[Anders Dinsen]

So... I know what I am doing tomorrow  .... however I seriously doubt that i will manage to get under the car by just jacking it up and using axlestands 

I can, and people tell me I have a big head!

Getting your big hands up to work on the alternator will not be easy though

Sounds like your old alternator only needs a new regulator, I've been told that these regulators aren't that robust. Good luck, I expect to be spending a bit time under mine too tomorrow, checking for an air leak. If that doesn't show anything, I'm going to check the carb as it seems some dirt is stuck in the idle jet as it can only be adjusted to run more or less lean in idle Perhaps my own fault when I did the gaskets?

[Lennart Sorth]

When Lennart is back from his christmas shopping in the UK ...

Christmas shopping yes, - but even more important: WHISKY TASTING at my old workplace :-)
Fantastic evening, 7 great whiskies, and then we drove home. (well, a non-drinker drove, of course) :-)

But the ampmeter in the dash still just barely rises above minimum

which of course is a "blowing-in-the-wind-VOLT-meter of sorts". As Anders discovered, it relys on heat difference by applying the potential to a small bi-metal flap. This gives a simple built-in dampening, but at the same time makes it ridiculously inaccurate, and  depending on the interior temperature as well.

However, if the charge-lamp flashes, then you may have a problem - but that could easily be the main +12V connector near the battery, or the fuseboard.

There is also something about the chargelamp being an intrinsic part of the charging circuit, as it makes up a resistor, so it could possibly be designed to glow faintly under high loads. Roy Gillard write an article about this in a MECUK magazine some 10 years ago or so - I'll see if  can find it faster than he responds to this thread :-)

I seriously doubt that i will manage to get under the car by just jacking it up and using axlestands 

Thats no problem.
Getting OUT is worse.

My wife often jokes that even if I used to tan easily in the summer, nowadays (read: since I bought my Murena) I only tan below the knees .... point taken :-)

/Lennart

[krede]

Removed the alternator from the car today... as it turned out the fanbelt was extremely loose, easily allowing the rotation of the alternator pully by hand!!!. could this have anything to do with all my troubles?? 
Anyway...Ill go on and fit the new alternator anyway, but the belt is unusable as it is now badly worn... I'll ahve to go and try to find a replacement of some sorts tomorrow.

[Anders Dinsen]

Removed the alternator from the car today... as it turned out the fanbelt was extremely loose, easily allowing the rotation of the alternator pully by hand!!!. could this have anything to do with all my troubles?? 

Ooups!! That would have been an easy check had it just been easy to get your hand down there! A loose belt isn't something you want to run with on a Murena given the criticality of the water pump!

Anyway...Ill go on and fit the new alternator anyway, but the belt is unusable as it is now badly worn... I'll ahve to go and try to find a replacement of some sorts tomorrow.

Good luck with that

[macaroni]

Right , quick update. I completed my mammoth 600 mile weekends worth of driving without incident. The car performed beautifully. It even returned 26mpg on the motorway, cruising at a steady 140km/h.
It even survived a 2 hour crawl across London last night.

I forgiven it last weeks tantrums.

[Lennart Sorth]

I have now found the article about the Murena charging light in the Matra Enthusiasts Club magazine Nowember 1995. - (For those who have it, its the yellow one with David Piper's M650 on the front)

The message is that the alternator needs a little current to start doing its job, and in the old days, this current was simply provided by the charge-bulb alone. However, that was in the days when 2.2W bulbs were the norm. Later it became standard to use 1.2W (as in Bagheera and Murena) which gives too little current, so there is a resistor wired in paralell.

BOTH the bulb and the resistor must be intact and wired up, in order for the alternator to work correctly.

Bulbs can easily be checked by substitution, but the resistor needs to be measured with an ohm-meter. Easiest is of course to remove the bulb and check that there still is a circuit.

The alternator light is fed through the fuseboard, so poor connection here can also affect the system.

Good things to check, before condemning the alternator.