twingo alternator not working

[paullap]

Hi can anyone explain to me how a Renault Twingo alternator works and how to test it . it has the big Red wire to the stater, and the other wire from the plug goes to the Body Control Module. if I disconnect the plug should the alternator be charging, I have rad that this wire is an excite wire and it might need to activated to get the alternator working. if so how can I do it to see if the alternator is working.


Thanks


Paul

[white exec]

I'm sure someone will be able to help with this, and identify the small wire's function.
Just a word of caution: do not run the engine/alternator with either the battery or the alternator supply/sensing wire disconnected, as this can damage the alternator's electronics.

[Hell Razor5543]

Does the relevant light on the dashboard work? If this bulb fails, the exciter circuit may not work, as the bulb (assuming it is a light bulb) is a part of the circuit (not sure how it works of the light is an LED).

[white exec]

Good point, James. Some are LED, some a filament bulb. Quite a few have a resistor in parallel with the bulb to cater for bulb failure.

[paullap]

Hi Thanks for the help, The bulb is working as it comes on after about 30 seconds. I have have 12.4 volts at the battery KOEO and engine running, no change,


Paul

[paullap]

I have just done a code scan and it has a DF137 UCH- Alternator connection, I dont have a clue what a UCH connection is. also I have put a scope on the exciter wire and has a square waveform very much like a can signal.


Paul

[JonAlexander]

Hello Paullap

Any updates on how to resolve the issue?
Im faced with the same problem on my renault twingo 1,5 diesel from 2012.

[ekjdm14]

Not sure you'll get a reply from paullap seeing as the account hasn't been logged into for over a year.

I'd expect to see a PWM signal into the exciter terminal I think.

It's possible if the car has sat for an extended period of time that that the exciter may need to be "flashed" by applying a current-limited 12v source to the terminal momentarily with the engine running. I've done this before using wires connected to a 1.2w dash illumination bulb & touch it across both terminals for about a second with the engine running. Would be cautious doing this on a more modern car, I'd likely have the exciter unplugged (& engine off) so as not to backfeed the car's electronics in any way if I tried it at all.

Another possibility is the brushes are either worn or sticking, this can sometimes be diagnosed by "percussive therapy" to the rear of the alternator with engine running which can jar them loose long enough to confirm them as the issue & order a replacement set.

Any "redneck/old-school" testingor fixes like this should be carried out as a last resort & in the knowledge that if one makes a mistake it can cause additional damage

[xantia_v6]

I am guessing that this is a controlled alternator and the control wire is a LIN bus. If so the alternator is self-exciting and does not require any voltage on the control wire to start charging. If you disconnect the control wire from the alternator, it should start charging at a constant voltage, this may cause a fault code to be thrown, but is an easy test.