Eco mode and flashing battery light, won't start

Hi . I have a 53 plate 1.4i C3 . Recently the battery warning light has been coming on intermittently . Yesterday it has been constant . Had the alt checked and output was 7 on idle . Replaced with s/h one from a pug 206 . Fitted fine . Had to jump start as eco mode was on . Started fine . On test battery light came on with a ping , 100 yards later airbag light on , just after lost steering . Pulled over . Eco was on . Interior light flashing , battery flashing , no electric windows . Wont turn over . Jump started first time all normal . Got home , 1 mile . Tried bsi reset . Still eco mode , wont start . Jumped again , no issues . Battery is 1 year old . Checked the pug alt as it had 2 wires on it 1 red 1 white compared to just 1 on my old alt with just 1 white . The white ones are on opposite terminals . Could this be the problem ? Or maybe battery is too low to charge but started fine before I had the alt checked . Confused as

Hi,

With no electric windows and other electrical faults, start by checking all the fuses.

There are 3 fuse boxes, one of them is hidden under the bsm fuse box.

The tips section has info on where to find the fuse boxes on a C3

Checked battery . Completely dead . New battery , all sorted but suspect alt will need checking by a pro .

Just another little question . Does it matter that the white wire on the c3 alt is on the opposite side to the one that was on the pug 206 replacement ?

You might think so but if your battery light is not on you would assume the charging system is OK.
If you have a volt meter you can check the charging system.
Probe the actual lead (The chemical element with the symbol Pb, stupid English language) post of the battery, not the electrical clamps. Without the engine running the reading should be about 13V. With the engine running it should be about 14V. No matter what the voltage reading is, with the engine running, it should rise by about a volt above the non-running voltage.
If the voltage is down (less than 13.5v) while the engine is running put one probe on the +ve lead terminal and the electrical clamp, note the voltage. Do the same for the negative terminals. If there is a voltage reading, that terminal connection is dirty. If there is no voltage between the post and the clamp and the voltage does not rise when you start the engine, then the alternator is not working.

Doing my nut in now . Driving on motorway , fine . Got to a country lane doing 20 . Battery light on . Main rd , light off . Village , light on . At work idling , light on permanently . Auto electricians in the morning if it gets me 30 miles to home .

It sounds like you might have replaced your bad alternator with a bad alternator. Battery terminals clean and free of corrosion? B+ terminal nut tight on the alternator? Earth strap from gearbox to the chassis sound? Accessory drive belt adjusted tight and in good order?
The only other thing it might be is a bad connection between the alternator and the engine ECU (that white wire you were talking about).
You just have to hope that it plays up when the auto electrician looks at it.

Thanks . Next door neighbour is an auto electrician . He got back off holiday today . Apparently 206 and c3 alts are not always compatible . Possibly earth fault from alt-starter-battery . Hes checking in the morning

Faulty second hand alt . Got a new one and fitted it . After 2 mins engine light off . All sorted . 120 mile drive last night no problems . Nipped to shop , battery light came on for 2 mins then off . Had new alt tested . Producing 11.9 and 11.4 under load . Can only be a dodgy earth I think but where are they ? .

Phatboy69 wrote: ↑Thu Aug 08, 2019 7:36 pm Had new alt tested . Producing 11.9 and 11.4 under load .

At the B+ terminal on the alternator? It should be 14.2-14.3 volts!!! With the car idling you wont draw enough current to get the alternator voltage that low! If you turn the aircon, the lights on and move the steering wheel backwards and forwards, it might dip below 14 volts at the B+ terminal. The worst it should ever get is in the mid 13 volt range, at the battery terminals, for short periods of time (E.G. aircon compressor running). Below 13.8V, at the battery terminals, the battery will not receive a charge. You will get voltage loss along the cable from the alternator to the battery. So B+ voltage is typically higher than battery terminal voltage but an extreme case might be as much as a volt.
Where were the voltage measurements made? If they were made at the B+ terminal, the earth strap is irrelevant you still have a problem with your alternator.
At this point I don't know exactly where the earth strap is but look for a thick green and yellow cable going from the gearbox to the chassis.