SOLVED...Alternator Issue?

The section for all Megane I talk.

Moderators: q292u, Ray, AndyAdmin, Stranger

Dizzwold
Posts: 4
Joined: Fri Jul 31, 2015 2:05 pm

SOLVED...Alternator Issue?

Postby Dizzwold » Tue Dec 29, 2015 9:42 pm

Hello Folks,

I have an odd issue here and just wondered if anyone else has had a similar experience or any advise.

Before Christmas the aux drive belt was making some noises. On inspection it was shredding, so got a new one. While removing the old belt, the alternator pulley was found to be the cause and falling apart.

I opted to buy a new alternator. The old unit was rated at 87amps 'Bosch 0124 325 031, Renault 7700434899', but went for the 'higher output alternative, Renault 7700101274', of 98amps as the vehicle has aircon. The following two links state this;

https://www.universal-rotating.co.uk/Pub ... ef=UNA1282
https://www.universal-rotating.co.uk/Pub ... ref=UNA495
I would like to make it known that I didn't purchase the alternator from the above company! I'm only using this as referrence for the part numbers!

The only difference is the ampage output and the DFM wire, but the DFM shouldn't cause an issue as the car only has the one cable for 'L', the warning light.

I later brokedown with a flat battery, so purchased a new battery. After a new alternator and battery, the battery went flat again, suggesting a faulty new alternator.

So i've now done a voltmeter test after bench charging the battery. I put the leads of the voltmeter on the battery 'while connected to the car, + to +, - to -', get a reading of 11.87volts. I then start the engine, the voltage drops for a second or two, to around 10.??volts, then peeks at 11.4volts, then the voltage slowly starts droping around 0.01volts a second while the engine is running.

From what I know, when starting the engine the voltage may drop for a second or two, but should then rise to about 2volts above the battery reading with the engine off?

I've contacted the supplier of the new alternator, and they have been realy good about this and offered a replacement or refund.

Am I correct in stating the alternator is at fault?

All very odd and would appreciate any input.

Regards.

Dizzwold.
Last edited by Dizzwold on Wed Jan 06, 2016 7:30 pm, edited 1 time in total.

AlexB
Driving Legend
Posts: 4307
Joined: Tue Mar 22, 2005 8:17 pm
Currently Drives:: Renaultsport R.S.250 Cup

Re: Alternator Issue?

Postby AlexB » Fri Jan 01, 2016 8:50 pm

When the battery is charging, it's voltage should be above 12V, and about 14V when fully charged. Your's is not charging.

It can be an incompatible alternator, defective alternator or a wiring fault. There's no way to tell.
AlexB
(no, a different AlexB)

Dizzwold
Posts: 4
Joined: Fri Jul 31, 2015 2:05 pm

Re: SOLVED...Alternator Issue?

Postby Dizzwold » Wed Jan 06, 2016 7:44 pm

Hi All,

AlexB, thank you for your input, and thank you to all that read my post.
I've now solved this issue, and can confirm the higher output version is compatable. I was correct regarding the readings taken from the battery and then starting the engine with the meter still connected to the battery. The voltage should rise somewhere between 14.2v-14.7v.
The new alternator was faulty, and for reasons unknown to me was actualy sucking extra life out of the battery.
I took some film of the fully charged battery with voltmeter connected then started the engine, and you can see the life draining out of the battery.
I will also take some film of the new, new alternator to show what should happen. I just now need to figure out how to attach video to this thread???

Regards.

Dizzwold

AlexB
Driving Legend
Posts: 4307
Joined: Tue Mar 22, 2005 8:17 pm
Currently Drives:: Renaultsport R.S.250 Cup

Re: SOLVED...Alternator Issue?

Postby AlexB » Thu Jan 07, 2016 9:40 pm

In order to attach a video, one needs to publish it somewhere else, e.g. on YouTube, and then include the link in the posted message.

I understand what an experiment you've done, it makes sense.
AlexB
(no, a different AlexB)


Return to “Megane I”

Who is online

Users browsing this forum: No registered users and 1 guest