MatraSport Forum

I fitted my car with a 80 amp alternator from Simons, about a year ago.
Ever since, the charging lamp and indeed the charging itself will first start after the engine reaches about 1500-2000 rpm.
As the mercedes gd240 we have in the army does the exact same thing, I haven't given it much thought.

However, the engine management I have had fitted recently, will only run properly after the alternator has "kicked in".. resulting in me having to immediately rev the engine to 2000 rpm every time the engine is started up.. witch Is both annoying and noisy.

Now is this reving to get the alternator to charge a fault? or a known Murena issue?... and in the case of the latter, can the alternator be modified to start charging straight away?

Would the solution be so simple as to change to a different alternator all togeather?   

It's not a situation I can recognise.
Could it be just a poor battery?

Nope... its always done so.

But original alternator was developing 55A - couldn't be that the reason? Or if You have the old regulating relay, you can try to change it if the problem isn't in it???

Isn't the regulation relay build into the alternator?

It's not a relay, it's a piece of electronics that ensures that the output voltage is 14.4V independent of the rotational speed of the input shaft. It does so by switching the current flowing in the stator coil. It has a 'starter' circuit which feeds a small current to the stator coil through the charging lamp.

It is built into the alternator, but on the older alternators it's a replacable part that can be removing by loosening a couple of screws. On newer ones, it can't be seperated.

either way it comes with the alternator in question.. so I reckon that its not to blame.

On all Murena/Tagora alternators I have ever seen was black plastic box mounted by 2 screws on the back side and very easy to demount. Also this box includes 2 carbons on springs. My mother had this problem on her 206: sometimes it wasn't charging, after knocking on this plastic box, it started working. The reason was that carbons was jammed inside.

the alternator wheel could be to big or the wheel on your engine could be to small resulting in to slow movement for the alternator.

try changing some of them

First question is, since this is a non-standard alternator, what make is it, and is the pulley diameter the same as the original Paris-Rhone A13N10?

Second, the Murena 2.2 and this Paris-Rhone was unusual in having to have an ignition feed to the alternator for it to work.  Most alternators only need a live power supply and the warning light connection through which it energizes, so how is this non-standard alternator wired?

Third, the Murena has an 82 ohm resistor wired across the warning light, which no other car I have ever come across in all my years in the motor trade, has ever had.  You will notice if you look very carefully, that as you turn the ignition on, there is a slight delay to the warning light coming on, due to this resistor.  Why was this resistor fitted?  I've always thought it was because the current that the 1.2 watt bulb passes was too small to energize the alternator (since they always used to use a 2.2 watt bulb).  However, I'm not positive.  If the bulb was blown on a normal car (without resistor) the alternator would not energize and would therefore not charge*, but on the Bagheera and Murena it will as it can pass the energizing current through the resistor (although it doesn't always charge properly but that may have been those particular cars in question had other problems like worn brushes).

So the warning light on the Bagheera and Murena appears to be mainly so that you get a visual indication of under or overcharging.  However, with your non-standard alternator, if it is the type that only requires a live feed and the warning light bulb connection, is the resistor actually causing the problem?  This would be easier to answer if I knew exactly why the Matra engineers put it there in the first place!

Assuming the warning light comes on immediately you switch the ignition on, then the alternator is getting some energizing current.  However, if the alternator has to be revved to 2000 rpm to get the warning light to go out, then it does not appear to be producing enough voltage until it is revved, which may be because it has insufficient current to energize it properly.  If the resistor is required but it has blown, it could be the reason.  Have you checked it?


It is not an issue with the standard P-R A13N10 alternator.  If anyone else has this non-standard alternator, can they tell us if they have this delayed charging symptom?  Did you question Simon about this effect after fitting it originally?


Well as I said there should be no problem with the original, but then you only have a max. of 55 amp output.  Mind you that should be sufficient for the Murena - it has never been a problem with any of my cars.  To require an 80 amp output you would need to be using some serious electrical equipment.  Do you have anything that makes this necessary?

* Cars with self energizing alternators will work without a warning light bulb, but they have totally different charging systems with separate warning light controls etc. and are not often seen now.

Roy

I know that people who are tuning their cars and using huge music aparature, they are mounting bigger bateries and due to this, they are using alternators with higher output, is this Your reason why You have 80 A alternator?

Krede has yet to show the details on this forum, but he has converted to EFI a few weeks ago. Injectors, fuel pump etc need a good deal of current. That said, however, I think most people choose the 80A alternator from Simon as it's priced almost the same as the 55A and gives a better "safety margin". On the other had it could also challenge poor/worn wiring. But if it doesn't charge until the engine is rev'ed I would say the advantage turns out to be a disadvantage. I guess that's also what you are implying Roy. Thanks for all the interesting details you have shared with us, Roy! :)

- Anders

PS: I like your sig, Michal

I would have to be some serious audio equipment to compete with the Inlet roar... :)
No Michael... The reason why I bought the 80 amp unit is because, I am going to run the car with an electric waterpump...... and up until recently had plans of fitting a water cooled  turbo (needing a pumpe) and water/air intercooler (needing yet another pump).. and as I needed a new alternator anyway, I figured that the "safe" thing to do was to get the 80 amp one.. since, as people have pointed out,.. it costs more or less the same..

Could very well be....
There is a pretty obvious difference when the alternator kicks in (the lights are brighter etc)
Where is the resistor situated?

I'll ask Simons if they have heard about this before.
   

In the wiring loom right behind the instrument panel, as shown on my diagrams.

Roy

Right... thx.
I had a look at the alternator while I tried to fix my Clutch slave cylinder.
The alternator was meant as a "direct replacement" and thus the connector for the wiring loom on the alternator matches the one on the Murena.
Tha make of the thing was unreadable, but it said something like "cargo"..on it.

You can check if its the altenator or something else.
Take a lamp of 2.2 Watt.
Disconnect the wire from the L connection on the altenator (red/green).
Put a lamp of 12 Volt 2.2 Watt (standard charging lamp for most cars) on the L connection of the altenator, and connect the other connection on the lamp on a straight 12 Volt plus.
The lamp wil turn on with ignition on, and have to go out when the car runs.
If it still doesn't work youre altenator is the problem.

Well until it charges, it's just 'dead' cargo! ;D
Any info from Simon?

It works fine ONCE it has reached aprox 2000 rpm.. even at idle... it just has to have the one "kick" to wake up...

Right... So I wrote Simon and got the reply that they had never had any such trouble with the 80 amp alternator.

So.. the fault is either with the alternator, or in my car.
And it HAS to be solved, as it is surely messing up my ECU.
I found this out as I was trying to wake up my Murena after it's 3 months in hibernation.
Even though it had been disconnected.. the battery didn't have the juice to start the engine.. so It had to get "mouth to mouth" by my old Citroën..
And As it turned out... when cranking with ~13-14 volts the engine fired up at once.

Welcome home! :)

Hmm, it could be your battery giving trouble for the alternator to start up properly. I know you would hate to go there, but maybe you could send your mother so noone will see you: THansen has batteries to fit our cars: P/N 990000000063 or 990000000078 depending on whether you have + on the right or left (mine has been converted from the standard).

(http://media.thg.dk/DAT/pic/m/990000000063.JPG)

I seriously doubt that its the battery that's causing the trouble.

Well you can try to swap batteries with your citroen, just for a test.

I already did mate :)
 

Well in that case (and if it's wired correctly, but I you have probably checked that TOO!), I suppose the alternator is going back to where it came from. It won't be the first time a new alternator is defective!

Riiiiight... so this morning my baby started up by its own battery with no problems at all!!
Apart from the fact that the car now runs very poorly at low throttle settings..

I called and spoke to the guy who programmed the ECU for me , and he is pretty sure that its the throttle potentiometer that's gone out of alignment.
He says that he can easily guide me through the re-calibration... but I need my laptop to do it.
I'll have a go at it when it arrives from Kosovo. 

Cars are emotional machines! ;D
Good luck on the throttle pot reprogramming. As the throttle pot is the only load sensing device on your car, I can imagine it has to be kept well calibrated.

@ Krede
-----------
I changed my altenator for 1 out a 205 (see my other topic about it).
If I don't connect te wire that goes to the charging bulb, the altenator starts working if I rev above 1500 rpm.
Alfter that it works normal.
Maybe you have to look at that circuit.
Also the connector at the altenator can have the wires different.
The wire that was on L at the old altenator is green/red, but at my car it was changed in red.
Look carefull there because the other wire is + contact.
They both give + if contact is switched on, so a mistake is made easy.
If the wires are connected wrong way around, the car want stop running after contact is switched of.
Its funny to have the key in youre hand, while the car is still running.

During my job, I calculated 3,5 Watt in the bulb/resistor circuit.
It is possible that this is not suited for youre new Altenator.
I described a bit back in this topic how to test.
Take a bulb 12V 0,25A and put it between B+ and (L or D+)
The Altenator has to work normal if you do so.

As it turned out, the "charging" issue had noting to do with my car running poorly.
So I don't really want to mess about with it any more.

I have replaced the battery with a more powerful "service free" one, since the smaller "standard" one has seen better days.
I tell myself that this has actually made starting up more trouble free.

Your symptoms sound like a classic case of a fault in the warning lamp circuit.  The lamp is connected to the field windings on the rotor via the slip rings.  When the ignition is switched on, the field current is supplied via the lamp and the lamp lights.  This continues until the alternator is providing enough output to supply its own field current, at which point the light goes out because there's 12 volts on both sides.  The parallel resistor is there to ensure that the alternator will still function if the bulb fails.  In your case, this is not happening and you are relying on the small amount of residual magnetism in the rotor to kick things off, which is why it has to run up to 2000 rpm before anything happens.  If the external wiring in the lamp circuit is ok then the alternator is faulty.
Peter