Have I bo**oxed my alternator?

[pig]

Just been fitting a water temperature gauge, it's the capillary type, just needs a 12v feed for the iluumination inside the gauge.

I accidentally touched the live return from the bulb to the control panel.......

Now the engine will only turn over if I disconnect the charging warning light on the control panel. The engine starts and runs ok until I reconnect the warning light, whereon the engine labours, the warning light is illuminated, and I stop the engine. With the warning light connected the starter motor will not even turn.

I suspect the 12v return from the bulb touched one of the lucas connectors on the warning light. The engine wiring diagram shows this wire going to the alternator "B" terminal.

Any idea what I've done?

If it is the alternator, can it be repaired or is it new alternator time?

 

Thanks for any help

Neil

[RLWP]

Hi Neil,

 

If you take the belt off the alternator, will the engine start with all of the wires on? I'm not suggesting that you run it for ages like this as the pump won't be running but it will be OK for a few minutes.

 

Richard

[pig]

Hi Neil,

 

If you take the belt off the alternator, will the engine start with all of the wires on? I'm not suggesting that you run it for ages like this as the pump won't be running but it will be OK for a few minutes.

 

Richard

 

Hi Richard, and thanks for your help.

I've just taken the fanbelt off, and the starter makes no attempt to turn the engine.

I also took off the 3 wires to the alternator,and again, no joy.

I'm afraid alternators are a mystery to me so your help is appreciated.

 

Hi Richard, and thanks for your help.

I've just taken the fanbelt off, and the starter makes no attempt to turn the engine.

I also took off the 3 wires to the alternator,and again, no joy.

I'm afraid alternators are a mystery to me so your help is appreciated.

 

just after I posted that, I tried with the engine charge light disconnected (alternator still disconnected and fan belt off) and the engine turned over and started.

[stuart]

Have you removed everything you "added" ? Does it work then?

[pig]

Have you removed everything you "added" ? Does it work then?

Yes, I removed the wire to temp gauge, and still no joy.

Thanks for helping

[RLWP]

Hi Richard, and thanks for your help.

I've just taken the fanbelt off, and the starter makes no attempt to turn the engine.

I also took off the 3 wires to the alternator,and again, no joy.

I'm afraid alternators are a mystery to me so your help is appreciated.

 

 

 

just after I posted that, I tried with the engine charge light disconnected (alternator still disconnected and fan belt off) and the engine turned over and started.

 

When you say "the starter makes no attempt" do you mean no clunks, clicks or anything else? Or is it trying and failing to turn the engine?

 

Richard

 

At the moment it sounds like a wiring thing - notoriously hard to diagnose by internet...

[pig]

When you say "the starter makes no attempt" do you mean no clunks, clicks or anything else? Or is it trying and failing to turn the engine?

 

Richard

 

At the moment it sounds like a wiring thing - notoriously hard to diagnose by internet...

The starter motor doesn't clunk, click or anything, with the engine charge light connected. Disconnect the engine light bulb and it works perfectly....

[John Orentas]

Have you removed everything you "added" ? Does it work then?

 

 

I very much doubt that the fault is with your alternator, but you may have some very strange interlocking circuitry.

 

Check for any circuit breakers you may have and reset them if tripped.. Check with the circuit drawing if you have one, a breaker could be hidden away behind the control panel for example.

 

Try disconnecting the start battery for a few seconds then try again..

 

Do any of your pilot or warning lights come on at all.

 

Is there any noise at all when you try to start the engine.

Edited July 10, 2008 by John Orentas

[RLWP]

I accidentally touched the live return from the bulb to the control panel.......

 

Hi Neil,

 

could you expand on this bit please?

 

"I touched the return and" - "Sparks flew and my hat blew off" - "I knocked a load of wires off but put them back where I thought was right" - "it was Ok I think I got away with it" - "FIRE!"

 

What happened?

 

Richard

[pig]

I very much doubt that the fault is with your alternator, but you may have some very strange interlocking circuitry.

 

Check for any circuit breakers you may have and reset them if tripped.

 

Try disconnecting the start battery for a few seconds then try again..

 

Do any of your pilot or warning lights come on at all.

 

Is there any noise at all when you try to start the engine.

Hi John

the engine is an extremely simple diesel- the wiring diagram has no electronics (bar 2 diodes inline with the warning buzzer and the oil pressure light and water temp light).

Likewise the boat has no complex electricals- split charge domestic/engine and that's it. No circuit breakers etc.

For me the behaviour when the engine is running, and I reconnect the engine charge warning light- the engine labours badly, and the fan belt slips a little- shows the alternator is not behaving normally,but I don't know enough about themto diagnose a fault.

I will take the alternator off- it's easy enough to get at- and I can measure the resistance between the terminals. Anyone know what resistance I should see across the various terminals?

 

Hi Neil,

 

could you expand on this bit please?

 

"I touched the return and" - "Sparks flew and my hat blew off" - "I knocked a load of wires off but put them back where I thought was right" - "it was Ok I think I got away with it" - "FIRE!"

 

What happened?

 

Richard

 

LOL

I was trying to find an earthing return for the temp gauge bulb. There was no firework display , but I realised that the wires to the charge light bulb were probably not the best thing to get12v onto. Sure enough the engine wouldn't start when I tried.

[RobinJ]

Just been fitting a water temperature gauge, it's the capillary type, just needs a 12v feed for the iluumination inside the gauge.

I accidentally touched the live return from the bulb to the control panel.......

Now the engine will only turn over if I disconnect the charging warning light on the control panel. The engine starts and runs ok until I reconnect the warning light, whereon the engine labours, the warning light is illuminated, and I stop the engine. With the warning light connected the starter motor will not even turn.

I suspect the 12v return from the bulb touched one of the lucas connectors on the warning light. The engine wiring diagram shows this wire going to the alternator "B" terminal.

Any idea what I've done?

Slightly confised here!

Sounds like you shorted out the 12V supply and should have blown a fuse etc.? (read always remember to isolate before working!)

In theory nothing should now work, but sounds like the warning light is causing a short?

Are you sure you've not swapped any connections over?

Try fitting another warning light with the original disconnected and see what happens. The warning light should be connected to the alternator at one end and the positive from the ignition switch at the other! If it runs OK, check the voltage to the battery is about 14V (ie alternator charging).

[Scotty]

... the engine will only turn over if I disconnect the charging warning light on the control panel. The engine starts and runs ok until I reconnect the warning light, whereon the engine labours, the warning light is illuminated, and I stop the engine. With the warning light connected the starter motor will not even turn...

So with the charging lamp connected, the engine labours as if the alternator is under a high load. That does sound like a short

[Sir Nibble]

O lordy!

Without being there, this is all likely to be futile. so, first thing, where are you? (or where is the boat more like).

At first reading I would suggest,

You have popped a diode,

A start relay is earthed thru the alternator and won't work 'cos it thinks the engine is running, (Due to the blown diode),

The alternator is lugging 'cos the blown diode is shorting a phase.

If you can find a make and part number off the alternator (or a pic) I could probably be quite specific about testing.

[pig]

O lordy!

Without being there, this is all likely to be futile. so, first thing, where are you? (or where is the boat more like).

At first reading I would suggest,

You have popped a diode,

A start relay is earthed thru the alternator and won't work 'cos it thinks the engine is running, (Due to the blown diode),

The alternator is lugging 'cos the blown diode is shorting a phase.

If you can find a make and part number off the alternator (or a pic) I could probably be quite specific about testing.

 

OK this is getting weird!

As suggested, the charging light is connected to the alternator, and the battery +ve.

So with the alternator connections disconnected, how is disconnecting the wire form the charging light making any difference?

I've left the +ve side connected to the light, taken off the wire that goes too the alternator- it starts... put that wire back on, it wont turn over.

I then noticed that spliced into the wire to the alternator terminal is a wire that goes to the split charge relay. Disconnect the wire to the split charge relay (with the charging light wire off) and it wont start!

anyway it's raining now so I'm pi**ed off AND wet!

Me and boat are in Wakefield on the Calder & Hebble

[Sir Nibble]

Me and boat are in Wakefield on the Calder & Hebble

Any techies nearby?

[pig]

Ok I've sat and thought and dried off a bit ,and I realise now what I've done to cause the problem, whatever it is. The lead I was waving about from the new gauge, was actually not floating at 12v,it was connected to earth, by virtue of the bulbholder in the gauge being earthed via the metal sender.

So I've earthed the connection to the alternator B terminal.

I dont know if this helps or not.

If I take the alternator off- is it easily tested by an auto-electrician?

Thanks for all your swift replies

[Sir Nibble]

It is most likely that somewhere along the line the start circuit is being broken by a relay energised from the alternator warning light terminal.

I suggest you put a meter or test lamp from the alt warning light terminal (wire disconnected) to the alternator casing. There should be no voltage present. If I am right in my first blind stab you will have 12V there. Do try and identify the alternator for me as I may well be able to put my hand on the correct replacement parts.

 

Ok I've sat and thought and dried off a bit ,and I realise now what I've done to cause the problem, whatever it is. The lead I was waving about from the new gauge, was actually not floating at 12v,it was connected to earth, by virtue of the bulbholder in the gauge being earthed via the metal sender.

So I've earthed the connection to the alternator B terminal.

I dont know if this helps or not.

If I take the alternator off- is it easily tested by an auto-electrician?

Thanks for all your swift replies

So I've earthed the connection to the alternator B terminal.

Probably blown a main fuse then.

If I take the alternator off- is it easily tested by an auto-electrician?

Yes, that's me, which is why I want to know what the make/type of the unit is, 'cos I can talk you through testing it in situ.

[pig]

It is most likely that somewhere along the line the start circuit is being broken by a relay energised from the alternator warning light terminal.

I suggest you put a meter or test lamp from the alt warning light terminal (wire disconnected) to the alternator casing. There should be no voltage present. If I am right in my first blind stab you will have 12V there. Do try and identify the alternator for me as I may well be able to put my hand on the correct replacement parts.

 

ok I've checked the voltage as you suggested, and i'mm getting 0.2v between earth and the terminal. I've now got the alternator off and I'm scratching away at the blue paint to see if i can find any details

 

 

right i've scratched away and i can see a number-

30AG8-00800

A71AO17

12V 40A

 

any use?

[pig]

Pictures of alternator here:

 

http://www.btinternet.com/~toothy/Altntr/

 

 

 

It is most likely that somewhere along the line the start circuit is being broken by a relay energised from the alternator warning light terminal.

Yep, had another look at the wiring diagram, and yes, the starter switch goes to a relay, the other side of which goes to the alternator. Why?

[pig]

apologies, I havent mentioned the engine type- it's a Sole Mini 26- a Mitsubishi 3 cylinder engine also used by Vetus I believe.

[Sir Nibble]

Right, I believe I have identified the unit, it's a Mitsubishi pt no A7T03277, (that's mitsubishi electric). The two small connections in the plug, they are arranged in a "T" formation, the stem of the T is the warning light terminal, the crosspiece of the T is an ignition supply. The test you already did looks ok, now check for a supply on that ignition terminal, (wiring side, key on obviously).

The start relay to the alternator is a safety interlock to avoid the starter being engaged with the engine already running (GGGRRAUUUUNCH! ££££££££££££).

I have other tests in mind, but start with this one as that supply is almost certainly fused and blowing that seems a likely result of your little accident.

[pig]

Right, I believe I have identified the unit, it's a Mitsubishi pt no A7T03277, (that's mitsubishi electric). The two small connections in the plug, they are arranged in a "T" formation, the stem of the T is the warning light terminal, the crosspiece of the T is an ignition supply. The test you already did looks ok, now check for a supply on that ignition terminal, (wiring side, key on obviously).

The start relay to the alternator is a safety interlock to avoid the starter being engaged with the engine already running (GGGRRAUUUUNCH! ££££££££££££).

I have other tests in mind, but start with this one as that supply is almost certainly fused and blowing that seems a likely result of your little accident.

ok I've checked the voltage at that terminal and it's zero. That's with all the other connections made and the ignition on.

There is normally no connection to this terminal- the lucas connector to that area just pushes on the upright of the T.

 

by the way I've sourced a used alternator for 80 quid, from the local Sole diesel agent. I'm tempted to snap it up, but I'd still like to repair this one , as when you're as kak handed as me a spare alternator seems like a good idea.

[Sir Nibble]

Well it sounds like you may well have bolloxed the poor thing. Re-fit it and we'll test it and see if you need a replacement.

[Nickhlx]

I was wondering if somehow the alternator main output has become directly shorted to earth with a thick cable ?

Can't see how that could happen accidentally though

 

Nick

Edited July 11, 2008 by Nickhlx

[pig]

Well rain almost stopped play today, but I got the 80 quid alternator and fitted it- but guess what- still the same problem!

I'm going to go over the wiring diagram and do some tests tomorrow if the rain holds off.

I'll keep you posted. Thanks again to all for your your time and help.

 

Neil

 

p.s. the supply for the split charge relay is tapped off the (red/white) lead to the alternator. Is this normal?

Edited July 11, 2008 by pig