xantia HDI not charging and no aircon fan

[Mandrake]

0004 isn't a cell (battery) its the charge light on the dashboard - eg a standard dashboard bulb. It's shunted by a resistor probably for two reasons - one is that a small bulb of that size is probably too high in resistance to provide enough current to the exciter terminal of the alternator to get it started, the other reason is if it relied entirely on the bulb the alternator would stop working if the dash bulb ever blew! (not very good for reliability...)

The feed to pin 7 of the air con ECU will just be a "sense" input - it measures the exciter terminal voltage and knows that if its near battery voltage that the engine is running and the alternator is charging, thus the fan is allowed to run. If it sees only a few volts it knows the alternator is not charging so the fan is disabled, as the cabin blower fan draws a LOT of current on high speeds, and would quickly run the battery down if your alternator failed while driving.

When you disconnect the wire from the alternator the bulb/resistor in the dasbhoard (0004) is able to pull the voltage to pin 7 of the aircon ECU up to battery voltage thus the fan runs. This suggests there is nothing wrong with the aircon ECU or its wiring.

If the bulb on the dashboard lights up when connected that shows the bulb is ok. The only other things it could really be is the shut resistor in parallel with the dashboard bulb could be faulty (but we have no idea what value it should be) or the alternator itself.

The way I understand the excitation terminal on an alternator to work (and I'm no expert) is that the bulb/resistor provides enough current to develop a few volts at the exciter terminal - enough to turn on the transistors that then supply current to the field coil. The alternator then starts producing output, which the middle three diodes on the alternator diagram then provide to the exciter terminal - this then becomes self sustaining, current is no longer required from the charge light so the light goes out.

Whether 1.3 volts is enough is doubtful, I would have expected maybe 3-6 volts or so. Again, that could either be the resistor in the dash or a problem with the alternator. If we knew what value the resistor should be you could connect one from battery to exciter terminal to see if it "kicks off". Mind you if you already tried a 5 watt bulb from battery positive to exciter terminal and it still didn't charge that strongly suggests your alternator is at fault.

[harryp]

Thanks for your fast and fullsome response! Will have to dismantle alternator then, after 'Ive done everything else. O Lord, what next eh? Again, thanks for your time!!!

[RichardW]

Harry

You implied that the alternator was charging if supplied with an external excitation? How did you check this - with a volt meter? If you just put 12V on the exciter terminal with the dash light still connected, then the dash light would probably go out, but the alternator would not necessarily be charging....! Is the alternator actually turning, and the belt not slipping? Removing the alternator on an HDi is not quite as hard as it looks, but it's not exactly a walk in the park....http://www.frenchcarforum.co.uk/forum/v ... hp?t=29797" onclick="window.open(this.href);return false;

[harryp]

Just re-checked; no charging at all now although fan still comes on with exic connection removed. Think it may have all been a nasty coincidence with the crankshaft pulley. Have read the 29797 epic! Thought that if bearings appear ok (using my large screwdriver stethoscope) might try and remove rear brush/comm pack if possible. Looks a possibility if I remove the oil filter, unless of course it houses the rear bearing. If so it's back to 29797!! Oh joy. Thanks again and regards, Harry.
BTW window problem was/is the rubber bush housing the window regulator pin in the glass is breaking up. Any idea of the citroen part number anyone??

[RichardW]

If it's a Bosch alternator, then it might be possible to get at the regulator / brush pack, although I remember there was a large nut that was difficult to undo. If it's a Valeo, then I don't think so, as I tried to get one apart, but needed a very slim deep 7mm(?) socket, and the bolts were all the way around the cap. For the work required, I'd take it out - you need a 16mm socket to undo the bolts. How many miles has it done? The slip rings on my original unit were pretty worn at 107k when I stripped it down.

One last try, start the engine and give the alternator a few good whacks with a hammer shaft... it might just be stuck brushes from it being stood.

[harryp]

Well, family gone and back on car...... no go on getting the rear off the alternator in situ, but seemed worth a try!! Have managed to remove 2 of the alternator bolts, adjacent to block near the oil filter housing. ..... but where are the other two and how do they come out? Stuck, as cannot find any pics showing fixing arrangement. Any info gratefully received!!

[Stewart(oily)]

Well, family gone and back on car...... no go on getting the rear off the alternator in situ, but seemed worth a try!! Have managed to remove 2 of the alternator bolts, adjacent to block near the oil filter housing. ..... but where are the other two and how do they come out? Stuck, as cannot find any pics showing fixing arrangement. Any info gratefully received!!

Theres a big one underneath, 21mm ISTR it does not need to come out, just unscrew it until it pulls a short way and the alternator should come upwards off the slotted mounting.

[RichardW]

Not on an HDi Stewart....

There are 2 bolts in from the oil filter side, and 2 in from the drive belt side - all are 16mm, and need to be fully removed. If you have removed the ECU box, the top bolt will be visible just above the chassis rail. The other is accessed from under the wheel arch, after removing the liner - I think this one is hardly visible, but easy enough to find by touch! There are conical spacers on some of the bolts that will probably fall out when you remove it.

[Stewart(oily)]

I stand corrected

[harryp]

Just back from Shrewsbury dealers collecting a pair of front window rubber glass grommets, only £1.70 the pair! Could hardly believe it after the £1000 plus quote for the front exhaust pipe..... That's a plus then! Even better, when I arrived back my Lexia was sitting on the doorstep. For info I ordered it from ukpolboy, took one hour from first contact, bank xfer, to putting out for despatch on Bank Hol Sat, collected yesterda and delivered today.... what superb service! As for the alternator, thanks as ever for the information; will make a brew, change and give it a go. BTW, I use an old 1/2 inch allen key ground down to 8mm on the tensioner and the tensioning can be done easily from underneath without having to remove the ECU box. Hmmm, wonder if I am going to have to remove said box to gain access to upper bolt..... Am also wondering if a Lexia session would have pointed any fingers??? Must stop wondering and get to it!

[harryp]

Just re-read your earlier post Richard. Car has covered 127k up to last Oct. Spinning the alternator on car, the bearings seem smooth anyway, so hope its just brushes and com.... I noted with horror it has been off road for a year, which accounts for rust on the disks! Shame on me.

[RichardW]

It's a lot easier to tension the belt if you wind the tension off the spring tensioner at the top.... Pretty sure you will need to remove the ECU box to get on the top bolt. Remove the engine ecu and lift out the brown relay. Undo 2 10mm bolts in the bottom of the box, then wiggle the box out - there is an air pipe at the front. IIRC you might need to unplug the AC pressure switch to get enough slack in the cable to get the ECU out.

[harryp]

OK, box out, bolts out, but cannot free the intercooler pipe so alternator is free but still behind radiator..... however have managed to remove rear plate on alternator. It is a bosch 150 amp and showing very little wear on either brushes or commutator. so where now? Going to try a diode test in situ if able. Does not seem to be a control pack in the alt, so maybe regulated by an ecu? Made me horribly suspicious that the fault is somewhere in the wiring?

[RichardW]

Regulator is in the alternator somewhere - there's only the excitation wire and the +ve that connected direct to the battery. Might be the diodes have gone belly up or one of the coils has failed. Should be able to get the intercooler pipe off - 7mm socket on the jubilee is the usual route if you can't get enough purchase with a screwdriver.

[harryp]

googling reveals that the brush pack contains the regulator. Jubilee clip is off but pipe "stuck" to spigot. Will persevere.... Regulators on ebay for around £28.