Ignition circuit and alternator help needed

[wijnendael]

Just finished fitting a new ignition switch on my diesel engine but now cannot get alternator to generate. As you can see from the circuit diagram attached the ignition switch connections are as they where told to me from the supplier. However i found that when turning on the keyswitch terminal 15 comes on and then when you turn to the pre-heat position it remains on, but when you push in the switch and turn to start the engine 15 goes off and 50a comes on. Initially i disconnected the start cable from 17 and connected it across the old start switch then turned on ignition used pre-heat and then pressed the start button everything started ok and the alternator was charging !!. After this i put a link between 50a and 15 and re-connected the start cable this then worked ok with ignition on, pre-heater cycle done and push and turn started the engine ok. There is one cable going to the engine that i am not sure what its for but without + volts to this when you try to start the engine will not start. I only hope that this has not damaged the alternator as it was only purchased new a couple of weeks ago. Can anybody give me any help on this hope the photo works ok
<a href="http://photobucket.com" target="_blank"><img src="http://i198.photobucket.com/albums/aa141/wijnendael/ignitioncct.jpg" border="0" alt="Photo Sharing and Video Hosting at Photobucket"></a>

 

[wijnendael]

whoops look like photo has not worked here is another try

 

[wijnendael]

Back again one more question, when i tried the new ignition switch and found out that turning it to the start position both lights for charge and ignition on went off as described above because he + volts on terminal 15 went off. Will this damage the alternator if there is no voltages to S & D+ ?

 

[mont]

Will post tonight - off to work now

 

[wijnendael]

Hi thanks for the reply, I await your posting. In the meantime I have been to the boat today to do some more work and while there thought i would start the engine and do some more tests on the charging circuit. And behold the alternator fired up and started charging the batteries. I run the engine for a couple of hours to put something back in the batteries and then stopped it. After a hour i thought i would give it another try and got the same response as yesterday (charge light on and no output from alternator. At least i know the alternator is not faulty as it worked ok on the first start, could this be something to do with using a neon lamp for the charge circuit ? or is it something else that i am missing ? unfortunately forgot to take some voltage readings before leaving

 

[mont]

See if this helps....
When faced with similar issues relating to alternator / rev counter / split charging diodes, after the third 'marine engineer / electrician' clearly had little more idea than me - and two alternators and one new diode later, I returned to basics and logic and eventually solved the problem with some research - incorrectly wired and jump wired.
So ...
As regards the ignition switch then I suggest you check again the wiring instructions fully. Without standing with you checking whats happening and when, its down to a schematic drawing and notes of what occurs and when and then sit and study if this makes sense.
Just because a wire is live at one end dont trust the other. Make up a jump wire to miss out the loom if needed to check something out.
For the Alternator charging issue.
I read your previous posts and see that you bought a new alternator which we must assume is ok as a unit and you say it has been 'charging' you think.
For the alternator to work properly it needs :-
1. Rotation from the engine to turn the pulley round - presume you've got this !
2. A reason to send out a charge. Battery demands a charge because its low on power due to engine starting or general drain of systems. The usually internal regulator inside the alternator which has a rating (often 14v ??) realises the battery is below this and sends a charge to the battery. If your shore power and your charger allows battery to get to 14v and your alternator is rated at 12v on regulator then theres no reason to send a charge and regulator senses this. Most nominal '12v systems' are often rated at 12.5 to 14v - equally alternators are often 14v (Volvo's often are) so check the spec's exactly so you know what your loooking for.
You say the alternators has been charging but with a problem system I would never trust a 'lights gone out' approach. Check it with the meter.
3. One I didnt know about until I got reading.
For an alternator to produce a charge it requires a permanent nominal '12 volt' supply. No basic feed and it doesnt 'excite' the alternator into producing an output / charge. Often this fault causes alternators to be binned / swopped when they work fine (cost me two recons - thanks ) as they simply just dont work / send a charge. Your alternator needs a permanent feed to it, usually at the back and this isnt done with the output cable going to the battery or split charger diode, when its in the charging situation - ignition switch is 'on' - engine should be running mode. This is often by way of a simple 1.5mm lead going into the back of alternator. Not to be confused with the revcounter feed (output) which is usual.
So if engine is running (or should / could be) then a permanent 12 v supply should be found going 'in' to the alternator.
4. Also DC electric runs in one direction from negative to positive. The negative is effectively the live.
5. Commonly the alternator provides the output for the revcounter. This is by way of a 1.5mm wire coming out of the back of alternator and up to the revcounter. This is the feed only wire and it should have variable voltage according to engne rev's. This is sometimes a tell tale of alternator wiring problems.
So ..
Just because you've got a new alternator it may be faulty but unlikely.
The ignition switch can directly affect the alternator as it is likely to be the source / cause of the 12v permanent feed, which enables the alternator to start charging.

The fix to me sounds like it just isn't wired correctly. It may be a poor connection somewhere causing intermittant faults but general electrics either work or they dont.
Not wishing to patronise but please do be careful with live electrics and pulleys and engines running etc. Do your new wiring to a high standard - clipped and crimped etc.
I think if you sit back and contemplate you'll solve this one yourself as you probably understand your own system better than anyone else already.
Hope this helps ...

 

[wijnendael]

Thanks for the information Mont, very useful reading. Tomorrow i will try the connection that goes from the ignition switch to the S connection on the alternator. At the moment this is switched through the ignition and on the previous old alternator i think it was connected directly to the + terminal of the battery (through the battery isolator switch). But i have also come to the conclusion that there must be something wrong with the new wiring and will no doubt find the solution (eventually) Thanks

 

[misterg]

[ QUOTE ]
could this be something to do with using a neon lamp for the charge circuit ?

[/ QUOTE ]

Say that again !?!?

Do you really mean neon lamp,? or do you mean LED or something?

Normally (AFAIK) the initial excitation for the alternator comes through the warning lamp, so this needs to pass a certain amount or current.

A neon lamp won't pass any current below about 50 volts, and will only pass a few milliamps after this. An LED will only pass a few milliamps full stop, and then only if it is connected the right way around.

Without excitation current, it is pot luck whether there is enough residual magnetism in the alternator to start generating or not. I would make sure that the charge warning lamp is the same type & wattage as the original.

Not an expert.

Andy

 

[wijnendael]

Hi the original start circuit also had a neon panel lamp fitted and i also assumed the same, but as i did not seem to have any touble with it i replaced with the same. I will try again today and if i experiance the same problem will connect a normal lamp in circuit around 2W and see if the problem disappears.

 

[misterg]

If it worked that way before it should work again ...... /forums/images/graemlins/confused.gif

Andy

 

[wijnendael]

Ok system working perfect now, made the S connection to a good permenant 12V+ and soldered a 2W lamp into the charge lamp circuit works perfect. Strange it was working ok on the old alternator with the neon in circuit.
Thanks for all the help everyone