The Mégane II Owners' Club

My new 56plate Megane 1.5dci is giving it's first problem after 2 days of owning.

After about 10-15mins of driving it comes up with a "low battery" warning on the dash, with the battery light and "stop" lights come on. The car continues to drive fine. It can be turned off and cold starts and hot starts fine and the warning goes, for about the first 10-15mins again. I have had the battery checked at the local auto shop, read fine. I have a volt meter over it and it reads 13v when turned off, 15v when running without warning lights, and 17.2V when the light comes on. Am I right thinking this is the alternator regulator? Which is built into the alternator and therefore needs changing?

I've had a headlight go tonight too which I think was from the high voltage.

17.2V is far far too high - 15.5V is the absolute maximum that the battery will tolerate (or for that matter the other critical systems).

I've read in the past that some alternators - not the normal type - have some degree of regulation controlled by the ECU. However, I believe that most Megane's are of the normal type, with the regulator internally mounted.

This can be repaired, rather than replaced. You will have to investigate which is the more economical route.

Be prepared to replace the battery also, since overcharging is nearly as bad as undercharging. To remove the 'surface charge', switch on the headlamps for 5 minutes then switch off and wait another 5 minutes, then meter the battery. It is a crude but largely effective test. Above 12.45V is good, 12.75V is better at room temperature (21C).

I suspect your diagnosis is spot on.

What happens, I guess, is that the UPC stops registering the battery voltage correctly and applies an overly high current to the exciter.

Check the left front wheel arch liner as usual, then the UPC connectors, then start tracing the wires by the circuit diagrams. I would imagine you have already checked to wires to the battery terminals...

AlexB wrote:Check the left front wheel arch liner as usual, then the UPC connectors, then start tracing the wires by the circuit diagrams. I would imagine you have already checked to wires to the battery terminals...

Thanks
I'm new to the megane what do you mean by checking the left front wheel arch liner as usual? i'd had a search but its quite vague to search for. What am I looking for? Checked the battery terminals, they are fine.

Edit, is it just the cover is in place to stop water spraying the electronic unit behind there? Even if it is not it shouldn't be a problem at the moment with the heat wave we seem to be having.

is it worth me picking up an error code reader?
this is quite close to me and I can get it today to test it tonight
http://cgi.ebay.co.uk/051-Renault-Megane-OBDII-Fault-Code-Service-Reset-2001-/220751249598?pt=UK_Diagnostic_Tools_Equipment&hash=item3365ccc0be&clk_rvr_id=346138395289#ht_2673wt_1051

anth1.5dci wrote:is it just the cover is in place to stop water spraying the electronic unit behind there

that's the one.

I didnt get the code reader, might get it tomorrow instead. Had the battery off and cleaned all the terminals, they were pretty nasty. The negative doesn't seem as tight as i'd like but it wont go any tighter. Hopefully it will be as simple a fix as that. But I am not betting on it. So I took some photos of the details on the alternator to try and see which one I need to get before taking it off. Here are the ones I took. Looks like is built for a VAG car

(sorry for the size I was trying to make them readable)



A pointer in the right direction to one that would fit would be great!

Yep, it is a wrong one. Your car is supposed to have an alternator rated 110 or 150 or 210A (depending on the spec). It is in the manual in the sticky thread. The alternator type must be programmed into the UPC.

fantastic, so how the hell is this one working??
how am I too find out which one I should have? Will Renault be able to tell me?
When I change it to the right one is the ECU/(is that the UPC) going to have a fit and not work?

Yes, they will determine the correct type by your number plate. Check them by noting the part numbers listed in the manual (MR364MEGANE1, section 16A).

Renault alternators are designed to provide a high current at low revs as well as under normal conditions. A way to achieve this is to have a bigger alternator, i.e. with higher rated current.

renualt dealers think its the 150amp bosch but don't know which one! local autofactors says it could be a fixed pulley or clutch too. I really don't know what to do next.

the other half uncle is good friends with a renault mechanic so he is going to have a look over it over the weekend for me.

gotta love second hand cars....

BOSCH 150A for k9k : LIE8 0 124 525 081 or ...82, installed since 2005. They use different regulators. Yes, your engine, apparently, uses a decoupling pulley, which is a one way clutch.

Did they ask you for the production number of the car when looking up the part? If not, then they just guessed. Try a different dealer, give them the production number and ask to quote the part number and price. Another option is to fit either of them and re-program the UPC.

AlexB wrote:BOSCH 150A for k9k : LIE8 0 124 525 081 or ...82, ......
give them the production number and ask to quote the part number and price. Another option is to fit either of them and re-program the UPC.

Where do i find the production number?

It is in your Maintenance Service booklet and on the oval plate on the B pillar on the driver's side (for 5 door hatch). It's called Fabrication Number and includes a leading letter followed with six digits.