Jump to content

Frustrating Electrical Fault


Featured Posts

Just before Christmas I was on my moored boat for a few days. As I usually do I check everything and start my Isuzu engine just to be sure all is ok and it was.

Between Christmas and New-Year we were on the boat again and on Thursday we decided we’d go for a short there and back trip along the North Oxford. However, when I came to start the engine there was nothing. Turning the key produced nothing. No lights. no alarm, no heat to the plugs and the engine wouldn’t turn. Everything was dead. I knew the batteries were well charged via the solar panels and the Shark MSC2612 charger but hauled the starter battery out anyway to check.  My multi-meter showed 13.5 volts across the terminals so, reassured by this, I put it back.

 

Back to the key now and still nothing! However, after some fairly blue language and a couple more tries the engine fired up and has done so every time I’ve tried it since. However, there is not the reassuring alarm when turning the key and the engine charge light remains firmly on but again the alarm is silent.

 

I’ve had the instrument panel open, cleaned all the terminals and sprayed with WD40. Still no change. The alternator was professionally fitted a few months back so I think this is unlikely to be the culprit but my other half then pointed out that the fuse warning light was illuminated on the  Shark charger. So, I disconnected the boat from the shore power, switched everything off and waited five minutes before lifting the Shark casing to change the 25A fuse. I tried to change the fuse  on three occasions but each time the fuse blew before I could insert it in fully. There were even a few sparks from the terminals.

 

We’ve left the boat now and I’m pleased that the solar panels will charge the batteries over the coming days thus saving them from damaging discharge. (They were showing 54% charged this morning and even after a few hours dull daylight had risen to 63%)

 

Frankly, I have no idea what is going on. Engine runs but charge light remains on but without the usual audible alarm. The Shark charger keeps blowing fuses but is now isolated. Are these faults related or just coincidence? Before I call for professional help does anyone have any ideas? I’d really appreciate any help and opinions.

 

Link to comment
Share on other sites

Stuff like this sometimes happens when the poxy plastic connection block becomes loose or dirty. The one that goes from you engine to the loom, They are dodgy at best and easy to tread on and loosen.

  • Greenie 1
Link to comment
Share on other sites

Thanks guys! Yes, one of those cheapies with the removable plastic red keys! Two in fact. If it is those what should I replace them with? I've also checked the plastic connection block. It looked ok. Interestingly, and something I forgot to mention, is that the rev-counter isn't working either and I read someone that takes a feed from the alternator. Could that be relevant?

Link to comment
Share on other sites

11 minutes ago, David Mack said:

Is your battery master switch one of those cheapies with a removable red plastic  key?

 

5 minutes ago, matty40s said:

That would be my first port of call to check.

They all seem to come from China and are crap! For turning off my batteries on the electric drive I have a Volvo truck one, it cost new 250 squids and is operated by a switch its for if something goes wrong kind of thing. 

Link to comment
Share on other sites

47 minutes ago, mrsmelly said:

Stuff like this sometimes happens when the poxy plastic connection block becomes loose or dirty. The one that goes from you engine to the loom, They are dodgy at best and easy to tread on and loosen.

 

This.

 

Especially as your instrument panel isn't working properly.  Clean it and tiewrap the plugs together.

Link to comment
Share on other sites

1 hour ago, JRT said:

I tried to change the fuse  on three occasions but each time the fuse blew before I could insert it in fully. There were even a few sparks from the terminals.

 

^^^This^^^ sounds a whole lot more complicated and serious than a battery isolator failing to make a good connection. 

 

25A fuses don't blow while they are being inserted unless "something" is trying to draw more than 25A. 

Link to comment
Share on other sites

Ref the 25A fuse problem - yes that's what my neighbour at the marina postulated too - something is drawing more than 25amps. What on earth could that be though? 

 

Link to comment
Share on other sites

11 minutes ago, JRT said:

Ref the 25A fuse problem - yes that's what my neighbour at the marina postulated too - something is drawing more than 25amps. What on earth could that be though? 

 

Is it a charger or a combined inverter/charger? Assuming the former, is the fuse between battery and charger? If so, the thing drawing more than 25A has to be the charger. Could be charging a capacitor across the output, although I wouldn’t expect that to blow a fuse (current wouldn’t be flowing for long enough), unless said capacitor has failed short circuit.

Worth disconnecting charger and checking resistance across output.

Link to comment
Share on other sites

If there is an intermittent poor connection between the start battery and ignition switch then the symptoms are as expected. My first suspect would be the master switch so either put both terminals on one stud so the switch is not in circuit OR screw a little ball of paper up and put it under the key. The ball will push the contacts tighter together. After that  definitely that multi-plug. It needs taking apart, inspecting and cleaning both halves and the typing together with cable ties. One around each cable entry and the one through those ties and pulling the whole lot together.

 

Explanation for why the symptoms are consistent with a poor feed to the ignition switch, assuming an intermittent connection. As long as it makes sufficient contact to start it and energise the alternator, and then vibrates to a "bad" position there will be little or no feed from the batteries to the instrument but there will be a feed from the field diodes back up through the warning lamps and onto the warning lamps and instruments BUT this feed has the warning lamp in series with it so there will not be sufficient current for the instruments to work properly and the warning lamp will glow.

 

Thinking about it this may be an ignition switch starting to go faulty and making an intermittent contact on the start terminal but a poor one on the Aux (instruments).

 

Rev counter. Yes the alternator sends it a load of pulses that alter their frequency with engine speed but it also needs a positive supply and a negative so if I ma correct that there is a problem with the feed to the ignition switch or aux. terminal it wont be getting the full supply on the 12V+ terminal so may well not work.

 

Link to comment
Share on other sites

I think you may have 2 faults.  

 

1 The battery charger has a short on the output, did you put yjr engine battery in correctly?

2 Ignition switch or dreaded multi plug in the engine loom.

 

You may have created on trying to find the other.

  • Greenie 1
Link to comment
Share on other sites

Thanks everyone. To answer some of the questions .....it's a charger not a combined charger/inverter. The fuse is a 25A spade type that plugs into the charger board. Sorry, I don't know where it sits in the circuit.  All I did to the starter battery was disconnect the clamps to the  two terminals, removed the battery, tested it and then put it back reconnecting the clamps to the terminals. I'm pretty sure it was all back the way I found it and don't think I disturbed anything else.

 

From what everyone has said it could be the master switch(s), the ignition switch, the multiplug or a combination of some or all. I know where to get new master switches and I can clean and cable tie the multiplug. Anyone know where I can get a new Isuzu marine ignition switch?

Link to comment
Share on other sites

1 hour ago, JRT said:

From what everyone has said it could be the master switch(s), the ignition switch, the multiplug or a combination of some or all. I know where to get new master switches and I can clean and cable tie the multiplug. Anyone know where I can get a new Isuzu marine ignition switch?

 

On an Isuzu, check the glowplug and starter relays.  They are in a small plastic box mounted on the engine itself.  If one of them is stuck closed they can pull over 100 amps through the 25A fuse ...

  • Greenie 1
Link to comment
Share on other sites

2 hours ago, JRT said:

Thanks everyone. To answer some of the questions .....it's a charger not a combined charger/inverter. The fuse is a 25A spade type that plugs into the charger board. Sorry, I don't know where it sits in the circuit.  All I did to the starter battery was disconnect the clamps to the  two terminals, removed the battery, tested it and then put it back reconnecting the clamps to the terminals. I'm pretty sure it was all back the way I found it and don't think I disturbed anything else.

 

From what everyone has said it could be the master switch(s), the ignition switch, the multiplug or a combination of some or all. I know where to get new master switches and I can clean and cable tie the multiplug. Anyone know where I can get a new Isuzu marine ignition switch?

 

Don't go buying parts until you have proven they are faulty.

 

I explained how to test the master switch.

 

As for the ignition  switch the easiest way is probably to run a length of cable from the engine battery pos to (say a screwdriver blade. Don't let the blade or any bare wire touch metal. Then get it running with the charge light glowing and the rev counter not working. Firmly touch the blade to the Aux terminal on the ignition  switch - the one that feeds the instruments and warning lamps. If the rev counter jumps into life then there is a very good chance the swatch is faulty.

 

As fro where to get one. By all means buy Isuzu if you want to but 12V Planet or Vehicle Wiring  Products will sell you a perfectly adequate one that does the same job for less. It is just a question f working out which switch provides the positions you need. 

Link to comment
Share on other sites

This is a bad year for delicate electrics, its relatively warm, damp, sunless, and unless little connections are really good then they will fail, if you have electrics under a cruiser stern then they are vulnerable, I would start by cleaning and drying anything that is obvious.

Link to comment
Share on other sites

Dielectric (silicone) grease is excellent smeared onto the electrical connector points, fuse blades, relays etc. It was always done once a year as winter approached on all my vulnerable electrics on a warm, dry and sunny day.

Link to comment
Share on other sites

https://www.arc-components.com/automotive-key-switches.html   Fourth one down, centre column; if you need one. It has a common key, so if you want a unique key you'll have to use one of the five position ones near the bottom of the page; just ignore the extra terminals. The five position one is also used on Vetus panels where you turn the key anti clockwise to stop the engine.

Edited by Eeyore
Link to comment
Share on other sites

  • 2 weeks later...

Fingers crossed, it's all fixed! (Some of you were right too!) My go to guy, after much deliberation and testing today, diagnosed the problems as 1. A loose connection on the starter solenoid 2. A couple of dodgy connections in the multiplug on the engine wiring loom and 3. Something stupid and embarrassing I did. He's fixed the lot it only cost me his labour fees. Thanks Ed!

  • Happy 1
Link to comment
Share on other sites

15 minutes ago, JRT said:

3. Something stupid and embarrassing I did.

 

You can't leave us hanging like that after getting free advice.  'Fess up! :D

 

 

Edited by TheBiscuits
clarity
  • Haha 1
  • Sad 1
Link to comment
Share on other sites

Glad the problem has been fixed.

 

As a point of information, the fuse rating of blade-type automotive fuses (which seem to be commonly used on boats) is the current at which the fuse is designed to blow. This is different from the way fuses used in electrical installations, 13A plugs, and electronic equipment are rated, where the fuse rating is the maximum current the fuse will safely carry without blowing. The max continuous carrying current of an automotive fuse is typically taken to be half its marked  rating.

  • Greenie 1
Link to comment
Share on other sites

14 hours ago, Ronaldo47 said:

Glad the problem has been fixed.

 

As a point of information, the fuse rating of blade-type automotive fuses (which seem to be commonly used on boats) is the current at which the fuse is designed to blow. This is different from the way fuses used in electrical installations, 13A plugs, and electronic equipment are rated, where the fuse rating is the maximum current the fuse will safely carry without blowing. The max continuous carrying current of an automotive fuse is typically taken to be half its marked  rating.

 

Not according to this site.

 

https://www.12voltplanet.co.uk/fuses-guide-uses.html

 

They say 12 volt fuses are marked at the continuous rating and quickly blow at about twice their marked rating.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.