Leonardo fuses

[Pinger]

I had the motor quit on me this morning, handily, at the garage where I was presenting for MOT so a fresh fuse was available which reinstated LPG operation. The lights on the LPG changeover switch died with the motor and all came back with a new fuse. My thoughts were that I had a short at the reducer solenoid (I'd slightly re-arranged the wires to avoid the possibility of a short but went the wrong way I think). Could a short there have blown a fuse (one of two - see photo) and if it did, would that account for the changeover switch going dead? Or is there something else should I be considering? Just to add, its been faultless since the new fuse was fitted albeit less than 5 miles to home. System is OMVL Millenium.

IMG_5746.JPG (1.46 MiB) Viewed 2887 times

[LPGC]

It depends how you've wired it but if you wired it conventional style (without fitting an additional relay) so the blue wire directly drives the solenoids then yes shorting a solenoid will blow the fuse because any load on the blue wire gets its power through the main Millenium red wire battery connection fuse.

But still the smaller fuse on the ignition switched live shouldn't blow because that just powers the coil of a small relay that's inside the Millenium that connects the Millenium to power via the red wire.

[Pinger]

Thanks LPGC.
The wiring in question is the legacy wiring from before my ownership so without knowledge of it I'll have to dig deeper and see what's what. Initially I thought a short at the solenoid caused it but as you say, that wouldn't shut down the rest of the system as evidenced by the lights going out on the switch.
Slightly worrying as I really cannot have the engine randomly quitting as overtaking on single carriageway roads is such a large part of my driving.

[LPGC]

Initially I thought a short at the solenoid caused it but as you say, that wouldn't shut down the rest of the system as evidenced by the lights going out on the switch.

A short at the solenoid would blow the main fuse which would mean the lights on the switch go out.

When conventionally wired (so no separate relay is used) there are 2 power feeds to the Millenium. One is the main power feed which powers the Millenium and any load on the blue wire to the gas solenoids. The other feed is ignition switched live which (if the vehicle has an efi fuel system) is often connected to the positive of a petrol injector instead of to the ignition switch. The ignition switched live wire is connected to a relay inside the Millenium which connects the Millenium to the main power feed.

In my last message I may have caused confusion by mentioning the ignition switched live wire and fuse but you didn't mention which of the 2 fuses blew and I wanted to be sure you meant it was the main power feed fuse that blew. The ignition switched live wire should only ever carry the few milliamps it takes to energise a small relay inside the Millenium so it should never blow regardless of if you short solenoids etc.

[Pinger]

Thanks again LPGC. Let me run through your post to check I've understood correctly.
I had another (only visual) look at the two fuses (both 7.5A) and cannot (without probing further) tell which is which - they both have the same coloured wires.
If I understand you correctly one fuse (the one that didn't blow most probably) energises an internal relay which when energised by the ignition key enables the main supply to the Millenium ECU and, the solenoids. If that is it then I'm fairly confident my rearranging of the wires (disturbed during the recent reducer rebuild) led to a short between the blue wire and earth - killing the engine when it blew the fuse and taking out the switch lights also. Please correct me if I've got this wrong.

Alas, any further diagnosis will be difficult as I don't think I can identify which fuse blew. I had the bonnet open, the MOT tester came over and I handed him the intact fuse. Then I pulled the other and when we realised it was blown he went to get a new one and for the life of me I cannot remember if I replaced the good fuse in its original location or, where the blown one had been. Sloppy I know but these things happen - or do with me around!

[LPGC]

That's correct, and the fuse that blew will be the main fuse not the the ignition switched live.

[Gilbertd]

From your picture they don't appear to have the same coloured wires. You have a Red, which is the ignition switched feed, and a Red/Black which is the permanent 12V. Although if you don't know which one blew then that doesn't help much.....

[Pinger]

That's correct, and the fuse that blew will be the main fuse not the the ignition switched live.

Again, thanks.
I'm thinking if the other fuse had blown (7.5A fuse handling mAmps) would that not have signalled or caused damage beyond what was easily retrievable with a new fuse?

[Pinger]

From your picture they don't appear to have the same coloured wires. You have a Red, which is the ignition switched feed, and a Red/Black which is the permanent 12V. Although if you don't know which one blew then that doesn't help much.....

Good spot!
If - and it is a bit of an if - the fuses went back where they came from, it was the plain red wired fuse that popped. But as per question in above post - wouldn't there have been ramifications beyond the easy fix that was possible?

[LPGC]

We expect it happened as you said and you'll be fine, you'll have blown the main power fuse that connects directly to the battery when it was running on LPG (so power to the blue wire) and you shorted the solenoid out.

There's nothing you could short out that should blow the ignition switched live fuse because it only supplies power to that little relay inside the Millenium that connects the rest of the system to power through the main fuse. The switched live fuse is there to protect the car's own wiring more than the LPG system wiring. To blow the ignition switched live fuse you'd need to remove the cover off the Millenium and short something out on it's circuit board or cut the wire between the Millenium and fuse and short it. Of course there is an extremely tiny chance that corrosion or something on the Millenium circuit board caused the ignition switched live fuse to blow or that there's a problem with the ignition switched live wire between it's fuse and the Millenium but the chances of those are so tiny they're hardly worth a mention. From everything you've said it's obvious you simply shorted the solenoid which blew the main fuse as it should, you don't need to be concerned, we don't expect you'll have any more problems.

[Pinger]

Thanks LPGC and Gilbert_d both of you have been an enormous help and have put my mind at ease re this happening again - especially given the potential danger.

My stupidities: when I was working on the reducer finally the crimped aluminium connector to its solenoid providing the +ve feed annoyed me enough to replace it with a soldered brass spade. Alas, without an insulating cover. The earth wire there has a soldered wire tagged such that there is an earth tag secured to the solenoid retaining bolt. I allowed the two to come into contact hence the short. That will be remedied today.
Then the stupidity of having the two fuses removed simultaneously and losing sight of which one blew. In my defence I didn't want to be wasting the MOT tester's time and, my head was swirling with 'if I don't get this sorted and back running on LPG, will it pass the emissions test on petrol'. Doesn't take much to flummox me. Thankfully, you guys are here to rescue me from my stupidities. Thanks.

[Pinger]

A slightly strange occurrence that looked like a repetition.It was running on petrol (on the driveway) and I went to switch to LPG and the lights on the switch were dead. Pulled the fuse on the red/black (permanently live) wire, popped in a new fuse and all's good again. When I later checked the fuse I removed it wasn't blown and with it back in place the engine ran on LPG. At this point I can only assume its connection with its receptacle was below par. New fuse back in as it has a snugger fit.
I found the original fuse that started this thread and it is categorically blown.
Summary then. Original fuse already discussed blew for reason already discussed (short at solenoid) and today's woes merely a slack connection (possibly due to earlier fuse removal).
Only reply to this if you think I'm wrong or, you think there's something else I should be looking at.