HDJ 80 fusible links rating.

[Dave2000]

Whilst tweaking the wiring under the bonnet fine tuning voltage drops and so forth, I am also replacing the fusible links with 'midi' fuses.

I am right in the middle of a rush order of parts for a customer which will include the fuses to replace the links however, looking at the various wiring diagrams I am seeing ONE wire and ONE FL for the glow plugs rated at 50 amps. Checking my car I find TWO cables going through TWO FL's, both in the one box marked 'Glow Plugs'.

Under time pressure, I have flicked through various diagrams and cannot find a twin wire FL diagram, I also have the other twin FL's for the vehicles 'systems' but cannot get a confirmed rating for them either.

With time at a premium, along with a headache since this morning does anyone have this info, a diagram or can point me in the right direction?

EDIT: 1994 12 valve

TIA

Regards

Dave

 

[StarCruiser]

No concrete info Dave, but if all else fails, look at the size of the wiring the fuse is to protect. If it's the same as the 50A link then run with that. Not very scientific but might help. Also I think I've read somewhere they are colour coded. I don't suppose for a minute there are two the same but it's worth a look I suppose.

 

[Dave2000]

Thanks for the reply Starcruiser, with over 70 'views' and little response thus far, shows information on the FL's is a bit thin on the ground but it is early days. I have made an educated guess at the maximum load on the 80 system, and once I have the glow plug ratings I will have to go with that. I am a little more 'with it' this morning so will spend some time gathering info.

The thickness of the 'systems' cables would indicate around 60 amps per run, there are two cables for the glow plugs and a further two for vehicle systems. If I take the glow plugs out of the occasion as they are a temporary or short term draw, this leaves cabling for around 120 amps, given the stock alternator is 80 amps and should have enough amperage to cover worst case (continued draw) scenario's including fuel pump/lights/heater blower/HRW/wipers for example, and in the absence of further information I will go for a fuse of about 80 amps for systems (40 per cable), and of course 50 for the glow plugs as per the manual. I just need to see if that is 50A per cable as there are two, I will pull the link part and have root round there, the alternator will feed via a 150 fuse back to the battery.

I do have a clamp on amp meter somewhere in the workshop however, the accuracy of this will be suspect though as I have never removed or checked the glow plugs as they are not really needed to start a DI engine, to be accurate I would need to disconnect them all and test each one individually, not a difficult job but time consuming and a luxury I do not have at the moment, unless someone has this info scribbled down somewhere safe?

Thanks for your thoughts.

regards

Dave

 

[StarCruiser]

The thing to remember is that as a standard vehicle the load on any part of the system is designed and will not increase above a known figure for a known time. These fusible links are only there for short circuit protection, overload protection being provided by the downstream fuses or in some cases by the fact that the item they are serving will only draw or deliver a certain current (alternator or glow plugs for example). Once these conditions change (larger alternator or added load somewhere) then things can start to go wrong with the possibility of cables overheating, fuses blowing etc.

I have to ask, why do you want to change the fusible links?

 

[Dave2000]

Tried getting back to you earlier but the LC site has been down.

I do have a good grounding (pun intended), on vehicle electrics so know where you are coming from SC. 40 years ago you needed to squeeze the drivers sun visor on my Ford Corsair before the engine would start, no door handles just a magnet in a signet ring to open doors via solenoids and reed switches/solenoids, in those days it was the hot thing, nowadays it is history.

The main reason for the post is tidying up under the bonnet. I am fitting all new main cables/terminals/connectors and the FL's are looking a little old and tatty. Hence the reason I wanted to replace with a similar rating, I have a neat little fuse box, takes a mega fuse (alt to battery), and then a take off from the mega fuse to midi fuses, electric engine cooling fan 40A (normal VC fan no longer used), glow plugs 50A, vehicle systems?, and finally the power supply to the rear load area 30A, this powers my fridge and so forth.

Just hung up on the vehicle systems overall amperage, in the absence of further input I will go with a 'safe' rating initially and keep a couple of higher rated fuses in the glove box.

Thanks again,

regards

Dave

 

[StarCruiser]

Sounds like you've got a solid plan there Dave. I posted up some photos of the wiring diagrams I have for a 94 80. Might be some clue on there.

http://www.landcruiserclub.net/forums/showthread.php?t=56860

Edit- there's not much info on rating, and I don't know which model this is for but it does show some of the other fuses.

 

[Dave2000]

Some good info there SC. I spent some time this pm, looking at the OE manuals the fuse AM1 (50A) is a good start. The Glow plugs FL also 50A but still need to confirm if that is 50A per cable or the two combined. I may end up servicing and taking two cars to the ITV (MOT) station tomorrow as it seems the Easter holiday here coincides with a local fiesta.........now how did that happen? So it seems the holiday will start Thursday, Friday, Half day Sat, Sunday and Monday! Gotta love the Spanish!!

So all being well I will get to the LC on Thursday and see if I can fathom out the last FL, and also see if the glow plug wiring FL's run parallel, that would be good as it will be just the one Midi fuse, two for the systems and one for the electric fan. Rear wiring can come off the fused extension on the aux battery pos terminal.

regards

Dave

 

[StarCruiser]

You could try disconnecting the two FLs you suspect run to the glow plugs and testing for continuity between them. It seems a very odd thing for Mr T to split and run wires in parallel with all the extra work that involves plus the additional possibility of failure.

Pop some photos up when you can and I'll compare it with my 94 HDJ81

 

[Dave2000]

It seems a very odd thing for Mr T to split and run wires in parallel with all the extra work that involves plus the additional possibility of failure.

Pop some photos up when you can and I'll compare it with my 94 HDJ81

It does allow for a convenient place to join two wires that run in parallel, routing single heavy cable can be a RPITA.

I will try an get a shot tomorrow, I lost SEVEN AND A HALF HOURS today taking two cars for MOT, so need to make up some time or next weeks itinerary falls to pieces.

Regards

Dave

 

[Dave2000]

It does allow for a convenient place to join two wires that run in parallel, routing single heavy cable can be a RPITA.

I will try an get a shot tomorrow, I lost SEVEN AND A HALF HOURS today taking two cars for MOT, so need to make up some time or next weeks itinerary falls to pieces.

Regards

Dave

Done my ankle tendons and up to my knee in plaster, car work on hold.
Loads of 'bits and pieces' arrived and I can't play.

Regards
Dave

 

[StarCruiser]

[emoji20] get mended soon…

You too…


Just kidding. [emoji4]

 

[Dave2000]

Sodding nuisance it is! Took the dogs along the beach, returned to house, missed the step twisted ankle to one side. It hurt so much I said things like "oh blast deary me", well alright "%&$·"%&&&/ The air was blue!! I was big and brave though and did not cry .....................well not in front of anybody.

I stuck some ice on it but it still started to swell. Went to the hospital, in the door and showed my medical card, I was seen within three minutes by the assesment team, X ray within 10, given a pain killer jab and waited one and a half hours for an anti inflammatory drug to reduce the swelling. Plastered up and sorted, friends turned up and drove me to their home.


Brilliant system, from entering the hospital (which was busy with the bank holiday accidents etc.) to finished in two and a half hours¿

Staying at the aforementioned friends place at the moment, too many steps to get to mine, so a bit of an enforced rest I could do without.

regards

Dave

 

[Dave2000]

So now up and about again, I would like to give this thread a little shameless bump if I may?


Too late done it!


I opened up one of the fusible link boxes, the one marked 'Glow plugs, I found the black FL joins a black cable, the Blue FL joins a white cable, so two different size colour and size cables. The FSM give only one rating of 50 amps to AM 1 (IGN), this leave an unknown figure for the other FL. I also plan to change the other two FL's as well but, information on their rating is extremely thin on the ground, pretty much 'Googled out' now. Is it possible that 'Paynes' manuals may have a wiring diagram that offers more information? That reminds me, I have an '80' 'Max Ellery' manual in the garage, have to be careful with that though as there are one or two very bad errors in it.

Failing that I have the option of fitting fuses with low ratings and working my way up as they blow! And of course using FL's there is a bit of latency before they fail, so will have to factor that in so...anybody?

regards

Dave

 

[StarCruiser]

What sizes are the cables the links are protecting? May be useful to list what you have and what is known. Diameter of the copper could be translated to cross sectional area. It could then be calculated what likely sizes are fitted.

 

[Dave2000]

What sizes are the cables the links are protecting? May be useful to list what you have and what is known. Diameter of the copper could be translated to cross sectional area. It could then be calculated what likely sizes are fitted.

I did check that out as it happens SC, but it was a quick glance as I was packing up, looking at them I would have said 6mm for one and 8.5mm for the other, this confirms your comment about running two wires to one destination being unlikely. One being larger than the other means they would invariably end up separate somewhere.

The sizes would indicate a capacity of around 50 amp and 60 amp respectively? Obviously the FL's are different in thickness as well, at this point I think my quick glance and guess may be wrong? I am thinking we already know (via the FSM), that one FL goes to the ignition via AM1 and is fused at 50 amp, this leads to the assumption that the other (thicker) is to the glow plugs? I need to find out the amperage of one of the glow plugs, check it's voltage rating and then it's resistance and calculate the amps it would draw, I will have a chat with the local spares guy and have a root through his catalogue. Some glow plugs are rated at 11 volts and some even less, not the typical 12v you would assume.

If we say the typical glow plug is 10 amps, that puts amperage at 60 amps 6 x10, allowing a bit for surge, then the heavier cable would have to be rated higher than 60 amps which means the fuse must be less, perhaps 50amp? Of course that goes out the window if we find the GP's pull say 8 amps. Perhaps I have the cable guesstimate wrong?

Have to have a measure up asap,

regards

Dave

 

[Dave2000]

Just thought I would offer closure to this thread, the information may help someone in the future. The fusible link ratings still have not been found, so I took another route.

Exiting the fusible link connector box are two wires, I thought they were different sizes but, one had an additional sheath so, the cables (one white the other black) are the same size. I was going to decide on fuse size based on cable size but cannot do that. The reason being that despite the cables being the same size the fusible links are not. The connecting terminals inside the box are also different to prevent the cables being put on the wrong fuse. This means that somewhere in the loom is a cable of less capacity. So, I removed one glow plug and tested it with an ammeter in line and it pulled 7.8 amps @ 12.68 volts, within a few seconds the amperage drawn started to fall, and settled at around 6.8 amps, so with 6 glow plugs then we have a draw of around 41 amps, if the surge amperage across all six plugs is the same as the one tested, then overall surge should be ITR of 47 amps. We know the fuse will blow immediately at a dead short, as will a fusible link but I they were used as they could 'hold' a higher amperage for longer than a fuse. That was years back, nowadays fuse characteristics similar.

So, I have chosen a 60 amp fuse for the main glow plug wire, this is the black one BTW, and a 50 for the other slightly smaller FL, if I have the FSM right, this feeds the timer and relays etc. I am open to suggestions to lower those two ratings if there is a strong enough argument? I am thinking drop a 40 amp in there for the lighter FL?

To the ignition FL, we know the main AM1 FL is 50 amps as per FSM, this is coloured black with a blue tracer, so a 50 amp in there. The other wire (red) I am still unsure about that one, so I have gone with 40 amps, this is the lowest Midi fuse I had, I will order up a 30 next week, judging by the cable thickness that would be more suitable.

FWIW, midi fuses will take a surge close to double the rating, so keep that in mind if you plan on offering any thoughts on fuse choice.

regards

Dave