MatraSport Forum

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 ?
 

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

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

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? 

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!

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..

(http://img.photobucket.com/albums/v200/krede/80ampalternator1.jpg)
That leaves a certain red wire without any power.....
(http://img.photobucket.com/albums/v200/krede/blap1.jpg)
could that be causing the alternator to fail?.. and if so, is it just to connect the small red wire to b+?

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

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..

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 (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 (http://www.espace-murena.com/Fichiers/ManuelAtelier/Da3a403.pdf)

- Anders

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

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 :)

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...

Problem solved.... without any new wirering.
The solution was as trivial as it is embarresing.. so I will not trouble you good people with it..  ;D

Come on, spill the beans. We're all friends here!

He he.. ok then..... Its really rather silly...
After installing the alternator I started the engine to see if it was working/charging.. witch it wasnt.. apearnatly... well.. as it turned out.. the engine was cold!!... that meant that as I was bouncing the throttle to get the charge light to go out, the carbs was choking thus not reaching high enough rpm for the system to start charging.....doh!
Thus the fault had nothing to do with the "AL-TER-NA-TOR".. but everything to do with the "O-PE-RA-TOR"..

Guess we sourted out who is buying the beers tonight eh?..  ;)

HAR HAR HAR HAR!!! :D

Not to mention that we probably all could have done the same! ;)

The worst example of this I've had was when our first Espace broke down. It happened just near our house and I had it towed home. It took me ONE WEEK to figure out that it was the timing belt that had broken. Ok, I thought it couldn't be as it had been replaced just 11 months earlier, but still. I had ALL sorts of odd thoughts while I tried to figure out what was wrong. I even replaced an expensive cam sensor (I still have to old one). Fortunately the mechanic did the repair on his and the belt suppliers expense and only three valves were bent.

But my wife still pokes me with that one and I've promised her to let the garage handle her car in the future - besides, now it's registered as a company car so it doesn't make that much difference and my time is also expensive ;)

Well I did a testdrive, and so far things seem ok.. though the fanbelt are squealing again... so I guess I have to get underneth the murena once more... this time I will get someone to fasten the bolts for me while i pull at the alternator :)

Erhm, - I would expect the system to charge even in idle - with the choke on ?
I don't recall having ever seen the charge-lamp on under normal conditions - except while cranking, or after turning the engine off.

/Lennart

We have the same issue with the mercedes GD in the army... you also have to rev them a bit for the alternator to "wake up" :)..
After that it does charge in idle.
Anyway... tightened the belt again... and that seems to be the end of that.... :)

Hello,

I wish made the same on my murena 1,6L, it is possible ?

Have you got any ref ?

The wiring loom from the alternator needs to be upgrade by bigger wire section ?

Thank you

Mathieu