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Barrus Shire - Starter fuse


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The problem lies somewhere between the fuse and the relay. The starter works without blowing the fuse. OP states that the fuse is found to be blown when the starter fails to operate on the next start. If the fault were downstream of the relay there would be occasions when the fuse would blow during cranking which doesn't appear to be the case. It appears to be failing with the engine running. I would carefully inspect the wiring between fuse and relay for chafing which could allow a short as the engine moves on its mounts under torque.

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27 minutes ago, Sir Nibble said:

The problem lies somewhere between the fuse and the relay. The starter works without blowing the fuse. OP states that the fuse is found to be blown when the starter fails to operate on the next start. If the fault were downstream of the relay there would be occasions when the fuse would blow during cranking which doesn't appear to be the case. It appears to be failing with the engine running. I would carefully inspect the wiring between fuse and relay for chafing which could allow a short as the engine moves on its mounts under torque.

Why look for something simple when there are lots of technical things to worry about that could possibly cause it

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46 minutes ago, ditchcrawler said:

Why look for something simple when there are lots of technical things to worry about that could possibly cause it

Because I know enough about the technical things to see how unlikely that is. It's all conditional on accurate reporting of the symptoms of course.

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17 hours ago, Sir Nibble said:

Because I know enough about the technical things to see how unlikely that is. It's all conditional on accurate reporting of the symptoms of course.

 

18 hours ago, Sir Nibble said:

The problem lies somewhere between the fuse and the relay. The starter works without blowing the fuse. OP states that the fuse is found to be blown when the starter fails to operate on the next start. If the fault were downstream of the relay there would be occasions when the fuse would blow during cranking which doesn't appear to be the case. It appears to be failing with the engine running. I would carefully inspect the wiring between fuse and relay for chafing which could allow a short as the engine moves on its mounts under torque.

The good news is that there is only about 50mm between the inline fuse carrier and the terminal in the relay base on my spare build 06 engine, and likely to be a similar length loop between the interlocking fuse and relay holders on later builds.

 

The 06 (and earlier?) builds having the fuse carrier so close to the relay base means that there isn't room (or need) to rejoin the loom inside the flexible conduit that Barrus use, so the separate feed from the fuse to terminal 30 on the relay base is very easy to inspect for damage. A possible area of chaffing damage is on the wire from terminal 87 on the relay base to the solenoid where chaffing is possible where it passes inline connectors (used to attach the inline fuse carriers to the loom) inside the flexible conduit.

 

The same may not be true for the later builds that use the interlocking relay base and fuse holders, however the wiring is going to be very tight under there; making it much more difficult to inspect.

 

 

Edited by Eeyore
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1 hour ago, Eeyore said:

 

The good news is that there is only about 50mm between the inline fuse carrier and the terminal in the relay base on my spare build 06 engine, and likely to be a similar length loop between the interlocking fuse and relay holders on later builds.

 

The 06 (and earlier?) builds having the fuse carrier so close to the relay base means that there isn't room (or need) to rejoin the loom inside the flexible conduit that Barrus use, so the separate feed from the fuse to terminal 30 on the relay base is very easy to inspect for damage. A possible area of chaffing damage is on the wire from terminal 87 on the relay base to the solenoid where chaffing is possible where it passes inline connectors (used to attach the inline fuse carriers to the loom) inside the flexible conduit.

 

The same may not be true for the later builds that use the interlocking relay base and fuse holders, however the wiring is going to be very tight under there; making it much more difficult to inspect.

 

 

But if the wire from 87 were to short it would only blow the fuse with the relay energised and the starter would instantly drop out. As I said, all conditional upon symptoms being accurately reported.

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On 25/07/2020 at 18:15, Ouse on Board? said:

Has anyone had a problem with their starter relay fuse blowing? We have a Barrus Shire 40 and last year the 15A fuse for the starter relay would randomly blow, preventing the starter from turning. Its been fine for most of this year until yesterday when it happened once more and again today. According to the wiring diagram its called the Engine Start Control System fuse. It may well be similar on other engines.

I've got a pot of spare fuses but it would be nice to know if this has happened to anyone before and what they did about it.

Other engines do use a relay in this way, in a wide variety of applications, not just marine. 
Vetus show it as engine mounted on some of their diagrams, but no fuse.

Beta recommend it’s use (as an option) to overcome volt drop on long extension looms; using a Lucas 33ra style 60amp relay and a 40amp fuse.

You might wonder if the fuse is chosen to protect the relay contacts, someone with more knowledge than me will be along shortly to offer comment on that.

 

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While we wait for Barrus to respond to the OP.............The online Barrus parts books list the 15 amp fuse as applicable to all models. (I checked the 35, 38 & 40 models) They do not list a 25 amp fuse!

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3 hours ago, Eeyore said:

While we wait for Barrus to respond to the OP.............The online Barrus parts books list the 15 amp fuse as applicable to all models. (I checked the 35, 38 & 40 models) They do not list a 25 amp fuse!

Well, I'm looking my 06 manual as I type this and the circuit diag. shows the fuse as 25 amp.  (Barrus part no. RDG 1152)   Fuse 1 on left side of holder. The 15amp fuses don't supply the solenoid.

See pictures.

 

 

CIMG9818.JPG

 

CIMG9819.JPG

CIMG9816.JPG

CIMG9817.JPG

Edited by Flyboy
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The maximum current draw on that circuit is both solenoid coils together for maybe 100ms followed by a few amps for the hold in coil for as long as the starter is cranking. All reports are that the engine starts with no failure occurring actually during startup. 

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Cheers all, I am going to climb down and inspect with torch and mirror, no problem doing that. I have a new relay on its way and a bulk load of 15 and 25 amp fuses so can do a little experimenting (one thing at a time though). 

You would think being an avionic engineer this would be a doddle but I think we are blessed with much easier to follow diagrams (with internal workings of components). I hate working with coloured wires all leading to boxes, however Flyboys diagrams are much better to follow so i may steal those

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6 minutes ago, Ouse on Board? said:

Cheers all, I am going to climb down and inspect with torch and mirror, no problem doing that. I have a new relay on its way and a bulk load of 15 and 25 amp fuses so can do a little experimenting (one thing at a time though). 

You would think being an avionic engineer this would be a doddle but I think we are blessed with much easier to follow diagrams (with internal workings of components). I hate working with coloured wires all leading to boxes, however Flyboys diagrams are much better to follow so i may steal those

You can download the manual from here if you need clearer diagrams.

https://www.yumpu.com/en/document/view/50989992/shire-owners-manual-06-build-33354045-50-pdf-ep-barrus

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1 hour ago, Sir Nibble said:

The maximum current draw on that circuit is both solenoid coils together for maybe 100ms followed by a few amps for the hold in coil for as long as the starter is cranking. All reports are that the engine starts with no failure occurring actually during startup. 

So to be clear, that rather rules out a starter solenoid fault and as the fuse blows at other random times it suggest, as SirN said earlier its a short between fuse and the relay.

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8 minutes ago, Tony Brooks said:

So to be clear, that rather rules out a starter solenoid fault and as the fuse blows at other random times it suggest, as SirN said earlier its a short between fuse and the relay.

I could also be an intermittent short from pin 30 to earth in the relay caused by engine vibration.

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1 minute ago, Flyboy said:

I could also be an intermittent short from pin 30 to earth in the relay caused by engine vibration.

I agree but those relays today are usually in a plastic case and the guts are mounted on a plastic or paxalon base so unless highly contaminated water has got inside so it conducts from pin 30 to the coil earth pin such a  short is less likely. I am not sure we are getting the full symptoms because such a short is in my view unlikely but who knows.

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17 minutes ago, Tony Brooks said:

I agree but those relays today are usually in a plastic case and the guts are mounted on a plastic or paxalon base so unless highly contaminated water has got inside so it conducts from pin 30 to the coil earth pin such a  short is less likely. I am not sure we are getting the full symptoms because such a short is in my view unlikely but who knows.

Perhaps when the op gets the new relay he's ordered it will at least confirm or otherwise if it's the relay.  Intermittent faults are always a pain to locate.

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1 hour ago, Flyboy said:

Perhaps when the op gets the new relay he's ordered it will at least confirm or otherwise if it's the relay.  Intermittent faults are always a pain to locate.

My preferred method in cases such as this is to stick a couple of wires into the fuse holder to a headlamp bulb and try to provoke the fault by wiggling wires and components. In this case sitting on the deck and pushing on the engine with ones feet to flex it in its mounts. When the short is present the light will come on.

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4 hours ago, Flyboy said:

You can download the manual from here if you need clearer diagrams.

https://www.yumpu.com/en/document/view/50989992/shire-owners-manual-06-build-33354045-50-pdf-ep-barrus

Thanks for posting the link. In a perfect world the manual would also show the identities of the four inline fused scattered about the loom on my 06 build, but ha ho. (Yes, the starter control fuse is 25 amp)

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13 minutes ago, Eeyore said:

Thanks for posting the link. In a perfect world the manual would also show the identities of the four inline fused scattered about the loom on my 06 build, but ha ho. (Yes, the starter control fuse is 25 amp)

In the manual service parts list it does describe what each fuse does protect. It's in one of the pictures in post 34.

From Left to right on the wiring diag.    25amp  starter control,   15 amp  7Kw Alt. sub system (Travelpower) if fitted,  40amp Engine stop,  15amp Dashpanel supply.

You could pencil them in on the wiring diag. for easy reference.

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55 minutes ago, Flyboy said:

In the manual service parts list it does describe what each fuse does protect. It's in one of the pictures in post 34.

From Left to right on the wiring diag.    25amp  starter control,   15 amp  7Kw Alt. sub system (Travelpower) if fitted,  40amp Engine stop,  15amp Dashpanel supply.

You could pencil them in on the wiring diag. for easy reference.

Yes the descriptions are the same, it’s just that mine has 4 separate inline fuse carriers in different locations, just poking out through gaps in the flexible conduit. They never were, or could have been attached to the relays as shown in the picture. I’m ok with which is which, I just wonder how other owners were meant to know. ?

Edited by Eeyore
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5 minutes ago, Eeyore said:

Yes the descriptions are the same, it’s just that mine has 4 separate inline fuse carriers in different locations, just poking out through gaps in the flexible conduit. They never were, or could have been attached to the relays as shown in the picture. I’m ok with which is which, I just wonder how other owners were meant to know. ?

Understood, My fuses are in a block so much easier to do. Maybe Barrus couldn't get the blocks at certain times and improvised with inline fuses.

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