Hi all,

Charging problems are ususally caused by the usual suspects; battery, alternator, wiring/connections, charging circuit fuse. Here's a guide to tracing a fault with the wiring between the battery and alternator.

The most likely cause is a high resistance (bad connection) between the output of the alternator and the point at which the battery/alternator feed joins with the main supply feed to the harness.

To discover the location of the fault try the following tests with your multimeter in the order listed (all of the tests carried out with the engine ticking over and the meter set to DC volts unless stated otherwise):

1) Put the black (negative)lead of your meter on the -ve battery post (important: not the terminal) and put the red (positive) lead on the +ve battery post (important: not the terminal). With the engine running at tickover the voltage should be around 14v. If 12v then go to test 2)

2)keep the black meter lead on the -ve battery post. Put the red meter lead on the +ve battery terminal( the bit of lead which joins the cable to the battery post). If it reads 14v when it only read 12v on the post then the resistance is between the battery terminal and the battery post. Remove and clean both with emery cloth and replace having smeared with a copper-slip type grease. If not go to test 3)

3)keeping the black meter lead on the -ve battey post put the red meter lead on the -ve battery terminal. If you see more than 0.2v there is a resistance between the battery terminal and the battery post. Repair as in 2) above. If not go to test 4)

4)keeping the black meter lead on the -ve battery terminal put the red meter lead on the terminal where the largest cable is joined to the back of the alternator (put it on the threaded terminal itself, not the crimp connection on the end of the cable). If the meter reads 14v, the resistance is between the alternator and the battery terminal. Trace the cable all the way from the alternator to the battery looking for bad connections. Sometimes the big cable from the alternator joins on to the big cable on the starter motor before then going to the battery. It depends on the relative location of both items. If the reading is only 12v then the problem is that the alternator is not producing. This does not mean that it is automatically U/S. If so, go to test 5)

5) keeping the black lead on the -ve battery post put the red lead on the terminal where the small cable connects on to the back of the alternator. This is the primary feed cable. It should read 0v with the ignition off and 12-14v with the ignition on depending on whether the alternator is producing or not. If the voltage is 12v or less there's a resistance in the cable providing the primary feed. I don't know the wiring for your specific model but 99% of the time it goes like this.... The cable from the +ve battery terminal/alternator main terminal makes its way to the fuse box. It goes through a fuse and then through the ignition switch. From there it passes through the charging light on the dash and finally ends up as the small wire connecting to the back of the alternator. When the engine is not running and the alternator is not producing the light on the dash sees a complete circuit from the battery through the bulb and finding its way back to the battery -ve termional through the secondary winding of the alternator. The light glows. If the alternator is working and producing voltage (bad engineering description but it conveys the point) then you end up with 12v (or 14v) either side of the charging light bulb. Because the voltage is the same either side fo the bulb it doesn't glow.


If your charging light goes out when the engine starts, the problem is not your alternator. The power from the alternator is simply not getting to the point in the system where the lights (or other components) derive their power.

Check the battery terminals, the alternator terminals and the state of the wiring in between. With any part of the cabling disconnected try setting your meter to OHMS and measuring the resitances of the cables. If in sound condition they should read the lowest reading your meter can display. In any case, anything above 0.5 ohm is a problem and should be investigated/repaired.

It is unlikely although possible for your fan belt to be slipping and not to hear it. Pushing on the belt midway between engine andalternator pulleys you should not be able to deflect the belt any more that 20mm. However, if this was the problem your charging light would be lit on the dash.

Once the engine has started the condition of the battery is immaterial in this regard. All of the power consumed by the loads in the car are provided by the alternator, not the battery. After all the alternator still has to be able recharge the battery with all those loads switched on. The alternator capacity always exceeds the consumption of all the loads. The only time when this is not true is when the car has been modified and extra lights or a massive stereo has been retrofitted.

Hope this helps. Don't hesitate to ask any other questions.

regards

noz 8)

ps
these tests apply to any car in the world with a negative earth when looking for an alternator fault

Norrie, the other common problem is mysterious flattenning of the battery. My 16v estate (and my son's AX) suffer from this and we have struggled to find the cause/s. I know that the way to put this right is to pull fuses but don't have much of a clue as to how to go about it. Have you any tips on the correct method for sorting it?
TIA and slainte!
Wendham

Wendham,

No problem.

Make sure you have the code for your radio before starting. Make sure you have a charged battery installed in the car before beginning the tests.

Disconnect one of the battery terminals. It doesn't matter which one. Usually the easiest one is the negative (black) because it has fewest cables connected.

Take a multimeter and set for the 'amps' setting on the dial. If appropriate on your meter you may have to unplug the red wire and move to a different connector on the meter. Cleverer meters don't need the cables moving.

If you've disconnected the negative battery lead take the red lead of your meter and connect it somehow to the loose negative cable with the terminal on the end. Take the black meter cable and connect somehow to the negative post on the battery. In both cases you will have to find a way to keep the meter leads touching the respective points. You could tape them up with insulating tape or just hold them. You will need an assistant if you hold them. If you disconnected the positive battery terminal, reverse the meter leads as described above.

At this point you should be able to turn the ignition switch on (if you have a diesel car you should disconnect the glow plug relay before doiing this otherwise the currrent taken by the glowplugs will blow the fuse in your meter). The dash should light up as normal. Do not try to energise the starter motor !! Take a note of the amp reading on your multimeter.

Turn the ignition off, close all the doors and wait for the interior light to go off and the suspension electrovalves to de-energise. With the car at rest and quiet take a note of the new reading on the multimeter. The reading should be less than approx 0.2 amps.
Whatever the reading is, you can calculate how long your battery will last at that drain rate. eg lets say you have a 70Ah battery. This means the battery will give (from a fully charged condition) 70 amps for 1 hour or 1 Amp for 70 hours or any combination in between. Divide the 70 by the reading on your meter. The result will be the length of time the battery should last in hours.

If the meter reading is say 1 amp or more then you have something left switched on. The easiest method to find out what is causing the problem is to pull out all your fuses in the fuse box( and elsewhere) one at a time. At some point, when you pull a fuse the meter reading will drop to zero (or close to it. A small amount of current is needed to keep the clock at the correct time, the car alarm energised, the programmed radio stations and the little flashing LED on the dash. )

Once the fuse which cuts out the current drain is known, you need to refer to either the Citroen Owners manual or a car manual produced by a third party to find out what that circuit feeds. From that list, just disconnect each of the devices one by one watching for the meter reading to drop. When it drops, you have found your culprit.

The car alarm, if it goes faulty, is sometimes the culprit. Other suggestions could be the illuminating light in the glovebox, the boot light and charging circuit to the alternator.

If pulling out all the fuses doesn't cause the meter reading to drop it may be something which is connected before the fusebox which is causing the problem. You need to refer to a wiring diagram but the usual things connected before the fusebox are : supply to glowplugs (if a diesel), supply to starter motor, supply to main terminal on alternator. Again, disconnect one at a time and watch the meter readings.

Of course the prerequisite for these tests to be successful is that the problem exists when you go looking for it. If it is an intermittent problem and it's not there when you go looking, you're not going to find it. You would have to repeat the tests a number of times at random to find the fault.

I hope this has been helpful.

If you need any more advice please don't hesitate to ask.

cheers

noz 8)

Norrie, many thanks for that clear explanation. Son #1 will get the job of pulling the fuses one by one while I check the amps.
Slainte!
Wendham

Why does this forum insist on telling me my username is already taken? I KNOW it is - by me!
Wendham