Alternator Issues

[fletch_306]

Hi all

I had finally got my car ready for its MOT today and on the way to the test centre the fuse on the d+ line (voltage sensing?) from the alternator keeps blowing now am i right in believing that this would be an internal fault in the alternator?
I'm running the alternator from westfield and the fault only occurs under acceleration, during tickover nothing blows which is why i have never spotted this before. On the tiger this line also supplies the gauges and the fuel pump both of which i have tested and there are no electrical shorts on there lines? i know you guys are probably going to say just get a new alternator but is there a way of clarifying this is the case?
The alternator should be under warranty from westfield as i have only had it six months so i will contact them if that is the case.

thanks
Fletch

[stevel]

Hi Fletch, not sure what alternator/engine you are running but a well known issue with the Lucas alternator on a Zetec is running too fast giving overcharging issues.  The solution is a larger alternator pulley which reduces speed of rotation.  This fixes the overcharging issue but can give a flickering light on tickover as it runs too slow at low revs, the light goes out above 2,500 rpm on my Zetec engined Tiger.  Hope that help??

['The Gaffer']

What size is your fuse? A performance fuel pump can draw around 10 amps or an ordinary pump about 3-7A under load, plus your gauges maybe another amp or 2. Maybe worth a check you have sufficient rating.

Also if the fuel filter is getting blocked then the pump will draw even more current, especially on acceleration.

[fletch_306]

It blew a 25amp fuse which I had to use to get the car back to my garage. I'm going to get another alternator tomorrow so I can at least eliminate that from the equation.

[Iancider]

Hi Fletch

The pic below is the correct wiring. 


The d+ terminal is the bias current for the stator winding - the one that provides the magnetism for the rotor to generate against.  It should only take a couple of amps.  The fat Brown wires to the left are the output and the W terminal is not connected.  The Ground connection is through the mounting and the engine therefore has to have an earth strap for Alternator and Starter.  If it looks like that it is correctly wired.  It could be that the wire to the d+ terminal which is on the switched battery live circuit from the ignition switch (Should be Brown/yellow) also has other thing wired to it and taking to much current or there is the possibility you have an intermittent short to earth.  All of those are more likely than and alternator fault.  You could try putting an Ammeter in series with the d+ wire to see if it is drawing an excessive current.  If it isn't then you have to suspect that something else hanging on that circuit is.

Good luck
Ian

[fletch_306]

Thank you Ian I will have another look monday when I'm back home. I really have a feeling that it may be the regulator though which I am getting tested off the alternator by a guy at work on monday . if it is I really need to find out why it happened and a thorough check of the wiring loom is underway.

[fletch_306]

Finally got round to looking at this and really need help.

The alternator has two connections a b+ (I know this goes to the starter then to battery) then a d+ and this is where I get an issue. The way it was wired as far as I can tell this goes through a fuse which is shared with other systems then through the charge indicator lamp the fuse keeps blowing.

What is the correct way of wiring the d+ wire.

Need help as this is all that is holding me back from getting the car back on the road

Ian I have seen your post above but how to I isolate the feed to make it work correctly what does it need to connect to

Thanks in advance

[Iancider]

Hi Peter,

You should see that one or two big fat brown wires go from the battery via the solenoid terminal to the B terminal.  The d+ terminal should be connected by a white wire with a brown stripe if you loom code is British Standard - not guaranteed with a kit car.  The routing to the d+ terminal  is as follows -  12V positive via a fuse typically 5 Amps then to the charge indicator lamp then directly to the d+ terminal.  There should be nothing else on this wire at all but other devices could be teed off at the same fuse.  It is possible that something else on the same fuse is faulty. 

Test 1 disconnect the existing d+ wire and tape so that it cannot short to ground.  Take a totally new wire from the battery + via a fuse as a precaution and connect that to the alternator.  If the fuse blows then the fault is in the Alternator regulator.  If the fuse does not blow then there is something faulty on the primary feed circuit.  the most likely cause would be nicked insulation or a wire crushed against the chassis.

Test 2 the white brown wire should route to the ignition switch which in the ON position will connect 12V from the Brown wire to the White Brown or it might be a green until it gets to the fuse-box then become the white brown after that.  If in test one you have proved the fault to be in the wiring then you need to trace the wiring and look for shorts (it may be intermittent).  With the power off you test with an ohmmeter or test lamp to see if there is a connection to earth on that wire - you will need to disconnect the charge lamp and test either side of it.  If you can't crack it I could down to assist.

Good luck
Ian

[fletch_306]

Thank you Ian I know my next winter plan is a totally new wiring loom but think i may to bring that forward as it is a messy loom.

I will give both those things a shot tomorrow.

[fletch_306]

Well thanks to Ian's help I have figured out that the alternator is perfectly fine however after an hour or so I found that the section of wiring loom that comes from the same fused circuit for the d+ wire has so many small drains to earth and a couple damaged wires deep in the loom that I have spent the rest of my Sunday making up a replacement section of loom to splice in so I can remove the damage hidden by the previous owner. I am now hoping that this will solve the issues that I have been having.

[Iancider]

Good luck with it - it is always worth doing it right!

Ian

[fletch_306]

Well I have a smart looking loom even if it doesn't comply to any colour standards. It will however be well marked up with what each cable goes to. Fingers crossed all will be good come fitting time.