Murena Alternator

[krede]

Does anybody know what the little square box on the upper wire on the alternator is for?
My guess is thats some sort of noise filter.. but I’m not sure
I’m replacing the alternator of my murena with a 80amp one tomorrow ,in the middle console on the 55 amp there is a “L” and “+”  connection, where there is just the “L” on the 80 amp.... think I should worry ?
 

[Matra_Hans]

Hi
I have also changed my alternator from an 55 Amp to an 80 Amp.
The newer 80 Amp does only have 2 conections whole the old one has one more connection, that is no problem (I checked with Simon before installing)

regards Hans

[krede]

Do you mean in the plastic socket?.. there my 80amp has only one.. there are two connections on the alternator itself

[Anders Dinsen]

The extra + on the 55 Amp alternator is just connected to battery.

The "box" you mention is indeed a capacitor for noise filtering.

[krede]

The extra + on the 55 Amp alternator is just connected to battery.

The "box" you mention is indeed a capacitor for noise filtering.

Thanks Anders.. Ill get to work now then  ... gosh.. they didn't leave you much room under there (the murena engine bay) did they? 

[krede]

Now... about that square nois damper on the alternator.... where does the wire go!!.. I removed the wires completely by feel.. and Now i heve no clue.... I'd say it goes to the alternator + but im not certan..

[Anders Dinsen]

Now... about that square nois damper on the alternator.... where does the wire go!!.. I removed the wires completely by feel.. and Now i heve no clue.... I'd say it goes to the alternator + but im not certan..

Indeed it does!

[krede]

Well I started up the car.. and the chargelight doesnt go out (it did before)
The current at the battery is 12.6 with engine running, where it was just a above 14 with the old (faulty?) alternator

The only difference i can think of is that the new alternator is "missing" a + in the middle connection..
here let me show you..


That leaves a certain red wire without any power.....

could that be causing the alternator to fail?.. and if so, is it just to connect the small red wire to b+?

[Lennart Sorth]

I'll point you at my extract from an old MECUK magazine: http://www.matrasport.dk/forum/index.php?topic=305.0

I don't know, but it certainly sounds adventurous to use an alternator with less connectors than what the car was designed for. I'm sure there was a purpose for that extra wire; - however it could be the one that only runs to the diagnostic socket?

/Lennart

[krede]

however it could be the one that only runs to the diagnostic socket?

Yep from the look of the diagram that might be the case...
However I don't understand why all a sudden the alternator fails then..

[Anders Dinsen]

The extra plus on the 55A alternator goes to the diagnostic socket where it can be used to check the alternator - it's actually not directly connected to the battery plus but to the minus side of the rotor which is pulled to minus by the regulator thereby allowing the alternator to charge. On the diag socket it would show a pulsing signal on a working alternator.

Lennart is right that the charge lamp is a critical component as it supplies the current to power the rotor coil until the alternator starts producing energy by itself.

There is an 82 Ohm resistor fitted in parallel with the charge lamp up, this is probably critical.

The other side of the regulator needs an earth connection which it should have through the alternator chassis according to the docs, but if that isn't working properly the rotor is never energised and the generator will not work.

There could be a few bugs here

I found this link when I looked around for info on this:
http://www.1stconnect.com/anozira/SiteTops/energy/Alternator/alternator.htm

Espace-Murena has a diagram of the 55A alternator here:
http://www.espace-murena.com/Fichiers/ManuelAtelier/Da3a403.pdf

- Anders

[krede]

Well..  the thing that puzzles me is that the old alternator did charge, and make the chargelight go out... it only failed during heavy load.. witch I take Ot could very well have been due to the loose fanbelt...
I'll try to get some readings wether the alternator gets the "start up" current or not... otherwise i guess Ill try installing the old one and see if that makes the charge light go out

[Anders Dinsen]

I think there's something not connected on the new alternator, or it is defective but that is less likely. I suggest you call Simon first - he should know

[krede]

I think there's something not connected on the new alternator

Yahh sure seems like it... I dont know what that should be though...
I presume that the terminals are layed ot the same as on the 55amp. (sure looks like it though no witing can be found on the alternator..)
However...  the BIG RED wire go to the BIG connecion on the alternator... the plug gost.. well where the plug goes.. and the damper goes from the small connetion to the b+ (also known a th BIG connection)..... shouldnt really be that hard..

[Anders Dinsen]

I think there's something not connected on the new alternator

Yahh sure seems like it... I dont know what that should be though...
I presume that the terminals are layed ot the same as on the 55amp. (sure looks like it though no witing can be found on the alternator..)
However...  the BIG RED wire go to the BIG connecion on the alternator... the plug gost.. well where the plug goes.. and the damper goes from the small connetion to the b+ (also known a th BIG connection)..... shouldnt really be that hard..

There should be an additional earth wire somewhere that has to be connected to chassis. This is the ground connection for the regulator. I think this is what you call the "small connection", i.e. the ground side of the noise suppressor. From the above I think you are missing that. This is the engine room ground - it runs in the wiring loom and connects to the diag socket, to the ignition module and to a ground terminal, I think it's sitting above the ignition coil somewhere, but can't recall.

It certainly won't charge if that is missing as this is the ground connection for the rotor coil (the current running in that controls the output voltage of the alternator - no current, no output).

If this had been missing on the old alternator perhaps it could have charged a little by current flowing going by "unauthorized" routes? This may be the problem with the old one...