Hi All

I have a problem with my forg, whic revolves around the charging system. I hit a speed bump when it was -4C two weeks ago, and the alternator faulty warning came up on the dashboard. I got the car recovered by the RAC, with the man adamant about it being the alternator.

With him there, I pulled on the main cable which runs from the alternator to the battery, and his multimeter started reading 14.5V, so all good, broken/ fractured charge cable. I have replaced this, charged the battery and it is still the same. I pulled on the cable, the alternator kicked into life and I drove for 2 miles before the alternator stopped working again, with associated message.

Now the alternator is only 2 years old, and was a brand new magnetti marelli unit, when fitted. I have checked the cables and their anchor points on the alternator, and noticed that the field wire (grey & white striped cable) only reads 7.5V ish when ticking over, but I would expect something a lot closer to what the battery is kicking out, in order to magnetise the alternator and allow it to give some output.

Does anybody have any idea what voltage this field wire should give, so that I can eliminate this wire as the possible cause of the problem, or not, depending on voltage. If anyone happens to have a wiring diagram of the charging system for this mysterious beast, or at least an idea of where this wire comes from and goes to, then I would be eternally grateful.

The next process would be to look at the internals of the alternator, e.g. the regulator, are there any easy tests that I can carry out to establish the likelihood of the regulator being goosed?

Any help would be greatly appreciated.

James,
If its a 1.9JTD same as mine i can throw a multimeter on it tonight for you.
Tell me exactly where to measure voltage between.
Cheers,
Marty.

Hi I forgot to mention this fact, it's a 1.9JTD 115bhp. If you could kindly measure the voltage that goes to the white/grey black cable that runs down from the loom to the smaller terminal on the alternator, earthed against the engine block, that would be perfect.

If you could measure the voltage at both ignition on, and also with engine running that would be great, as depending on where I read, the voltage is high initially, but then drops as the regulator feeds the alternator this voltage, (which is why it runs with no battery on.), or this voltage remains static regardless of what the engine is doing.

I think its either a poor voltage at this cable, which isn't making the alternator generate power, or the regulator itself has broken the wire that runs to the alternator internals, either way cheap fix, awkward to get to to resolve the problem.

I appreciate your offer of help.

Cheers

James

Will do...

Been trying to acces altenator past twenty mins.
I've drivers side jacked up but I can't get near back of altenator... Have you followed cable into engine bay???... Lamp down the back of the engine and I can't see a thing... Id need to get it up on ramps to see I reckon...
Marty.

Hi Marty

Thanks for trying for me, it's a real pig to get to, as you say drivers side is jacked up, crawl underneath and right in front of your face is where the only accessible point is, its a real PITA. Tracing the wire is a problem made worse by the fact that I can only reach so far up from underneath, and from above, with the engine cover off, the loom disappears behind the bulkhead, and I can't reach it at all.

Having spoken to an auto sparky, he said that if you earth the wire that comes from this loom, if the battery light illuminates fully without flickering, then the faulty wiring is with the alternator, but if the battery light still illuminates and flickers, then the fault is in this wire. I have been on my arse tonight and I can report that once earthed, the battery light is on fully, which leads me to conclude that the alternator is duff after only 2 years and 25,000 miles. I must say that I'm not impressed!

My last test is to put a wire from the battery directly to the field wire terminal. If that does nothing to get the alternator charging, then it is definately the alternator and I need to remove that and get it fixed or replaced. I must say that I can hardly contain my excitement at that prospect!

Thanks for your help anyway Marty. I owe you.

it may just be a connection on the RECTIFIER has broke and needs resoldering if it was after a bump

Hi Dave

If it were to be something like that, would it easily re-solder, or would it be a case of renewing the rectifier and refitting with better connectors?

Also, can you take the rectifier off without removing the alternator on the Multipla? I think there is a slim chance that this can happen, but am not especially sure, and as you can tell am not looking forward to removing this SOAB this weekend!

Any help would be appreciated.

Cheers

James

you would have to take it off i reckon, there are repair videos on youtube and spares on ebay that can save lots of money though

Hi Dave

Thanks for your reply, I'll remove it, and once it's out I can have a look at it better. Hopefully I'll be able to identify the fault and repair it quickly and easily.

Cheers

James

JamesAtthews said:

... I pulled on the main cable which runs from the alternator to the battery...

Click to expand...

There are two cables on mine (115 JTD).
One connects the Battery to the Starter, the other links the same terminal post on the Starter to the Alternator.
If you pulled on the battery-to-starter cable, and the fault cleared (albeit briefly), then maybe it's a bad/loose connection at the starter.

Hi Bikedoc

Thanks for your post, I had hoped for this too, but when I put the multimeter on the terminal from the alternator that runs to the starter motor, there was no output whatsoever, just the same as was on the battery terminals, as I would expect.

Sadly I don't think there is anything that I haven't covered or checked with this now. The only thing that I'm going to try tomorrow before I remove it from the car is to run a power lead from the battery to the smaller terminal on the alternator, to double check that the power from the field wire isn't at fault here.

Fingers are still crossed for a simple, non invasive solution.

I used to be like that, optimistic to the last...

Good luck with the job if you need to replace it though, I've recently done mine.
Someone on here said you can remove/refit it without having to undo/move/remove anything else, but I couldn't see how. It's just physically larger than any of the gaps underneath, at least mine was.
I think there are two, maybe three choices that fit, Amps-wise, so maybe the lowest rated one is a bit smaller overall, but I took the option that was listed for mine.

Hi a thread i started in 2010 ' replacing the alternator 115 JTD' might be of some use for removal.

Hi Cooky

Many thanks for your post, I think I've come across it, but will make sure that I have a look before I start messing about.

Cheers

James

Hi

Just to update with the alternator, my car, a late model bug only needs a 105 amp alternator, checked via EPER and main dealer.

Removal of the alternator was, despite the various threads, a piece of cake. I removed the wishbone (needed replacing), removed the belt and undid the 2 bolts that hold the alternator to the car. I then jacked the engine up with a wooden block on the sump, and the alternator dropped between the subframe and driveshaft. Note, that I didn't have to unbolt the intermediate driveshaft bearing and support to remove the alternator, as some posters have done so.

I need to receive and re-fit the new alternator, but it should be a reversal of removal.

Thanks for your collective help with this.

Cheers

James

I don't suppose you took any pictures?

Hi

I didn't but I still have to get the other one back in so I'll get a photo of it when I get the alternator in the post.

Cheers

James

It's not the alternator itself, more the route that you used to get it out that I was curious to see.

I was thinking about this altenator prob myself and reckon loosening two engine mounts would allow you swing te engine forward enough to get it out.
Jacking on its own sounds good as long as not stressing engine mounts.
Marty