Perkins 4236 short circuit someplace - how to test ignition

[peteK]

It may be that your preheater is stuck on and thats what is causing ignition switch to get hot.

 

[shoc]

Now I'm in big trouble, the wiring loom/harness is no longer available from Perkins ☹ (part number 4172P002)

So I'll have to get a replacement made, would an auto electrician be suitable for this kind of job or are there loom/harness specialists?

 

[Deleted member 36384]

If it was me, I would remove the wiring harness from the boat. Layout on a table and carefully check systematically and then replace damaged items like for like. A lot of the connectors can be purchased online as they are universal parts. Terminals and proper crimping pliers are easily obtained. Advice can be found here on YBW. I do not think it would be too difficult. I also own a 4236, there is not much to the harness.

Alternatively, pin out the old loom so that all the wires and branches are at full length, then build a new loom copying the old one. Or look on line for old ones. Most boat looms will be custom lengths to reach switches and panels but easily extended.

 

[tillergirl]

I agree with 'BOB'. After all a loom is nuffin but wires and bits and bobs. I would suggest you follow the same colour coding - I got supplies from Cables | Automotive Electrical Supplies | Autosparks while extending the loom to a more distant panel. But that switch def. is duff if there is continuity twixt 1 and 2 while off, let alone 1 and 5. I shall now alway look at my ignition switch.

 

[179580]

12 volts supply Switch off. Negative
| ____________ \___________{ Load }_______________|
|________ 12 volt________|


12 volts supply Switch on. Negative
|__________________________{ Load }________________|
|_______ 0 volt__________ |

Sorry to labour a point but you said in a previous post you saw voltage between terminals 1 and 2 with the switch off. See the above diagrams. It is perfectly feasible to see 12 volts with the switch off.

 

[scottie]

Not this old chestnut again? Perhaps the diesel fuel in the OP's engine is never ignited?

Richard

Certainly not electrically
other than perhaps fuel supply or cut off a diesel does not require any voltage ?to run once started thereby negating the complications of an ignition system

 

[RichardS]

Certainly not electrically
other than perhaps fuel supply or cut off a diesel does not require any voltage ?to run once started thereby negating the complications of an ignition system

Glow plugs and starter motor are both electrical and are needed for ignition of the diesel to commence on many engines.

Richard

 

[179580]

Now I'm in big trouble, the wiring loom/harness is no longer available from Perkins ☹ (part number 4172P002)

So I'll have to get a replacement made, would an auto electrician be suitable for this kind of job or are there loom/harness specialists?

Where are you?

 

[scottie]

Glow plugs and starter motor are both electrical and are needed for ignition of the diesel to commence on many engines.

Richard

But not all is the point ?

 

[RichardS]

But not all is the point ?

And the point of post #3 was?

Richard

 

[scottie]

And the point of post #3 was?

Richard

Self explanatory??

 

[john_q]

I have a 4236 - since 1994 (which is Insulated neutral i.e Starter, alternator and allengine gauges have their own negative feeds, not through the engine).

The pre heat I had was on the inlet manifold, I have never used it and when the diesel feed pipe broke , I disconnected it at the engine fuel filter and never had a problem.

I l aso rewired the engine, as others have said it is not that complicated, I did not follow the Perkins wiring colours but was able to label (by numbers) each cable so I knew what it was. By using larger cables I was also able to get rid the the lovely rusty collection of relays at the back of the engine so less spares to carry

I also agree that the pre heat should only be powered up whilst the engine switch is held in the pre heat position, as soon as the key is released it is disconnected and the switches do go wrong, I am on my third one

Good luck

 

[shoc]

Thanks for everyones replies -its been very useful, I was back to the boat today so have some direction this time.

Where are you?

Boat is in Lanesborough Co Longford and I'm a hour and a half drive away.

12 volts supply Switch off. Negative
| ____________ \___________{ Load }_______________|
|________ 12 volt________|


12 volts supply Switch on. Negative
|__________________________{ Load }________________|
|_______ 0 volt__________ |

Sorry to labour a point but you said in a previous post you saw voltage between terminals 1 and 2 with the switch off. See the above diagrams. It is perfectly feasible to see 12 volts with the switch off.

With better concentration this time, I tested the connections again and found the following;

With the ignition key off, I had 12.7v between terminal 1 & 5. When I remove the relay (SRB500) the voltage drops to zero, so either a faulty relay or faulty pre-heater but since I don't need the pre-heater I can just disconnect it and leave it. I've ordered a replacement ignition so will fit that when it arrives. I have inspected the starter and alternators connections for any signs of scorching/burns and none found so I think thats the cause of the short circuit found and resolved.


Moving on, I have some wires behind the dash that are scorched and others have the outer insulation melted and need replacing, I reckon if I can source the cable and connectors then its just a matter of careful rewiring which I happy to undertake (and have the yard mechanic look it over when finished)

Some questions;

1) I believe these connectors are not made anymore, so what is the modern equivalent?


2) I need to replace about 9 different coloured wires behind the dash where they are scorched/melted and I see a huge selection on www.autosparks.co.uk but I'm unsure of what size wire I need. I've measured the existing wires with a calipers and have a variety of diameters 2.3mm, 2.7mm, 3.3mm & 4mm -- would anyone know the sizes that I need for this panel?



I will also need a selection of spade connectors in various sizes because I don't think they are all standard.

Final question, where I have a short piece of wire thats damaged, is it ok to replace that short piece with new cable by using butt connectors? I'm proposing this for the smaller sized wires not the 3.3mm & 4mm which will be replaced in full length.

Thanks for reading if you got this far...

 

[179580]

Thanks for everyones replies -its been very useful, I was back to the boat today so have some direction this time.



Boat is in Lanesborough Co Longford and I'm a hour and a half drive away.



With better concentration this time, I tested the connections again and found the following;

With the ignition key off, I had 12.7v between terminal 1 & 5. When I remove the relay (SRB500) the voltage drops to zero, so either a faulty relay or faulty pre-heater but since I don't need the pre-heater I can just disconnect it and leave it. I've ordered a replacement ignition so will fit that when it arrives. I have inspected the starter and alternators connections for any signs of scorching/burns and none found so I think thats the cause of the short circuit found and resolved.


Moving on, I have some wires behind the dash that are scorched and others have the outer insulation melted and need replacing, I reckon if I can source the cable and connectors then its just a matter of careful rewiring which I happy to undertake (and have the yard mechanic look it over when finished)

Some questions;

1) I believe these connectors are not made anymore, so what is the modern equivalent?


2) I need to replace about 9 different coloured wires behind the dash where they are scorched/melted and I see a huge selection on www.autosparks.co.uk but I'm unsure of what size wire I need. I've measured the existing wires with a calipers and have a variety of diameters 2.3mm, 2.7mm, 3.3mm & 4mm -- would anyone know the sizes that I need for this panel?



I will also need a selection of spade connectors in various sizes because I don't think they are all standard.

Final question, where I have a short piece of wire thats damaged, is it ok to replace that short piece with new cable by using butt connectors? I'm proposing this for the smaller sized wires not the 3.3mm & 4mm which will be replaced in full length.

Thanks for reading if you got this far...

With the key in the off position, that is what I would expect, see diagram 1. That test only proves continuity or a break in the circuit i.e the switch is the break in the circuit, therefore the switch is working correctly

The relay when not activated, isolates the heater, assuming the relay is connected to the heater. Therefore pretty certain to say the fault is the relay.

OR

You say some wires behind the dash have melted insulation. The same could be in the engine loom causing the short.

Connectors, see www.12voltplanet.co.uk multi-way connectors. You will need to buy a crimp tool for uninsulated connectors as well. Probably about £30-40

Butt terms are fine but cable support each side of butt for strain relief.

Cable sizing is somewhat a bit difficult. Are the cables AWG or Metric? Again 12 volt planet are your friend, if you select a cable and hit the specification button it will give you the OD and the current rating.

Spades are available in several sizes 2.8, 4.8, 6.3 and 9,5 as standard.

I have no connection with said supplier but an excellent source of knowledge and detail.

Hope this helps.

 

[179580]

Thanks for everyones replies -its been very useful, I was back to the boat today so have some direction this time.



Boat is in Lanesborough Co Longford and I'm a hour and a half drive away.



With better concentration this time, I tested the connections again and found the following;

With the ignition key off, I had 12.7v between terminal 1 & 5. When I remove the relay (SRB500) the voltage drops to zero, so either a faulty relay or faulty pre-heater but since I don't need the pre-heater I can just disconnect it and leave it. I've ordered a replacement ignition so will fit that when it arrives. I have inspected the starter and alternators connections for any signs of scorching/burns and none found so I think thats the cause of the short circuit found and resolved.


Moving on, I have some wires behind the dash that are scorched and others have the outer insulation melted and need replacing, I reckon if I can source the cable and connectors then its just a matter of careful rewiring which I happy to undertake (and have the yard mechanic look it over when finished)

Some questions;

1) I believe these connectors are not made anymore, so what is the modern equivalent?


2) I need to replace about 9 different coloured wires behind the dash where they are scorched/melted and I see a huge selection on www.autosparks.co.uk but I'm unsure of what size wire I need. I've measured the existing wires with a calipers and have a variety of diameters 2.3mm, 2.7mm, 3.3mm & 4mm -- would anyone know the sizes that I need for this panel?



I will also need a selection of spade connectors in various sizes because I don't think they are all standard.

Final question, where I have a short piece of wire thats damaged, is it ok to replace that short piece with new cable by using butt connectors? I'm proposing this for the smaller sized wires not the 3.3mm & 4mm which will be replaced in full length.

Thanks for reading if you got this far...

I notice from the image of the panel that the key switch has only 4 position legend. The legend is applicable to the 4 plate switch truth table, not the 5 plate.

Why 2 battery warning lights?

 

[179580]

Have just been reviewing the whole thread.
Worrying that you say the insulation is melted on cables with an OD of 6mm. That size cable is capable for about 60-70 amps!
From what we are given, you have more problems than just the switch, that you have proved is in fact breaking the circuit.
I would recommend you employ a competent electrician sooner rather than later.
With the size of cables and the current you are playing with can rapidly lead to a very burning experience.

 

[Deleted member 36384]

... Why 2 battery warning lights?

It’s a similar panel as my 4236 panel and I have twin alternators: house bank and engine start.

 

[shoc]

Have just been reviewing the whole thread.
Worrying that you say the insulation is melted on cables with an OD of 6mm. That size cable is capable for about 60-70 amps!
From what we are given, you have more problems than just the switch, that you have proved is in fact breaking the circuit.
I would recommend you employ a competent electrician sooner rather than later.
With the size of cables and the current you are playing with can rapidly lead to a very burning experience.

As far as I can see only two wires overheated (solid brown & solid white) which are connected to terminal 1 & 2 on the back of the ignition. The other wires are damaged only at contact points with the 2 that overheated and its mainly slight melting of the insulation that tore apart when I was separating the tangle.

I agree with you about getting an electrician but they are so busy that they really aren't available at the moment. My plan is to replace damaged wires myself and then have the yard mechanic inspect and be there for a test run and thorough check over.

I wouldn't plan on replacing some wires then casting off and hoping for the best -- the work needs thorough checking.

It’s a similar panel as my 4236 panel and I have twin alternators: house bank and engine start.

Yes I have two alternators

 

[179580]

Another question concerning the relay, it is marked as 20/30 A. That would indicate a change over relay. Are there 4 or 5 wires connected to the base?

 

[shoc]

Another question concerning the relay, it is marked as 20/30 A. That would indicate a change over relay. Are there 4 or 5 wires connected to the base?

Yes its marked 20/30 A and has 5 wire connection, heres a photo of the old and new;