411 fuse boxes

[peter dowdle]

Can any one help I have wiring issues with my 411. There are two fuse boxes the one on the left is powered through the ignition switch, the one on the right is direct powered from the battery. My question is does anyone know which fuses supply which parts of the car. There is no directions in the owners manual as to which fuse powers which units. I am mainly in trouble with the ignition circuits.

Thanking you

Peter Dowdle

[Geoff Kingston]

Peter,
If this link does not work I am sure Kevin will be able to help.
Geoff.
Resources - Bristol Cars - Owners and Enthusiasts Forum

[peter dowdle]

Geoff thank you but I have a copy of the wiring diagram in my owners hand book.

The wiring diagram shows a fuse but it does not tell you which fuse in the fuse box. You can work out if its direct power or ignition power but not which fuse.

Most cars have a diagram showing the fuse box and the fuses are labelled 1 to 8. I have had a melt down on the power side of the two fuse boxes but its very hard to sort out which fuse works which circuit

[Geoff Kingston]

Peter,
I have sold my 411 but still have a 603 which probably has a similar fuse box arrangement if you could post or send me a picture of the fuse boxes affected on your car I can check the layout on the 603 and if its the same I can pull the fuses individually to see what they protect if that would help.
Geoff.

[peter dowdle]

Geoff that is a very kind offer. I guess I could do that on my 412. Silly me I guess I just hoped some one might have actually known. Or even better the manufacturer, might have at some stage, actually told their customers, like all other car manufacturers do.

[Geoff Kingston]

Peter,
I seem to remember when I had my 603 we had to establish which fuse did what ourselves as the wiring was partly dismantled, it was a long while ago though, I should have made a note but didn't, I was told the 603 is the most difficult to re wire, the layout on your 412 is much more likely to be the same as the 411.
Geoff.

[Xseries]

I cannot recall where I found this now or the car it is for (will be a 411 or later), but it might help

1. Headlamp L.H. High Beam.
2. Headlamp L.H. Dipped Beam.
3. Headlamp R.H. High Beam.
4. Headlamp R.H. Dipped Beam.
5. Side/Tail; Number Plate L.H.; Ignition Switch Lamp; Glove Box: Panel.
6. Side/Tail; Number Plate R.H.; Boot; Rear Fog.
7. Rear Window.
8. Windscreen Wipers.
9. Headlamp Flashers; Horns; Fans; Clock; Cigar Lighters; Hazard Warning; Aerial Motor; Interior Lights.
10. Heater Motor.
11. Window Lifts.
12. Boot Lock; Fuel Filler Lock; Sunroof (if fitted).

Seat operation and Air Conditioning, with their own individual protection, are tapped off No. 12

FUSES — 4 from top

1. Fans Auto. Trigger; Speedhold; Brake Warning; Rear Window Trigger; Fuel Gauge; Fuel Reserve; Water Temperature Gauge.
2. Turn Indicators; Stop Lamps.
3. Fans Manual.
4. Reverse Lamps; Battery Condition Indicator; Air Conditioning Master Switch.

[peter dowdle]

than you XSERIES

My guess is this info is from a much later model. The 411 only has 2 fuse boxes with 4 fuses per box a total of 8. There are other single fuses spread around. I have managed by a process of elimination to partly sort it out. I am yet to compare the 412 to the 411 as my 403 is on my hoist with the brakes in pieces. All the wheel cylinders are seized from lack of use so I am taking the opportunity to fit a power booster and upgrade to silicone brake fluid.

[Patrick Kenny]

Hello Peter,

Don't know if it's of any help, but I'm attaching the relevant page from my 411 IV's handbook. My eight fuses are under two covers, also attached.

Best regards, Pat.

[peter dowdle]

Patrick

Thanks for that , yes thats the same as my MK2 it doesnt though tell you which fuse is which. My big problem is the power supply side of the fuses. I have power coming into the top fuse which seems to control the volt gauge . The 3 wires feeding the lower fuses are badly burnt and welded together which makes it impossible to tell where they fit. I have made up a wire which loops down from number 1 to the other 3 which means the car runs ok. This though leaves me with 3 feed wires, the reason for these I have little knowledge.

[Geoff Kingston]

Peter,
When we were working on my 401 I bought an electrical circuit tester/fault finder that had a battery in it to send a small charge down a wire which you could pick up at the other end, I would suggest if you bought something similar and followed the description of circuits protected in a previous post then by a process of elimination you will find the answer, or use it to confirm what the feeds in and out serve and then replace the fuse boxes with a newer multi fuse box and have every circuit individually protected which now I have thought about it makes a lot more sense, a upgrade for my 603 is on the cards.
Geoff.

[Kevin H]

Peter,
Do these photos help (see attached)?

It would be good to see a photo of your problem also.

Regards,
Kevin

[peter dowdle]

Thank you Kevin and Geoff for your help.

Kevin the first photo you posted is of the fuse box which is supplied with power from the ignition switch. You would note there are a lot of white wires coming in to the right of the box, these are all I believe power into the fuses. Where they come from and why there are so many defeats me. The white wires are the ones that burnt. Is it possible to get another photo taken a little further back to help me trace the white wires to there source. The condition of your loom appears to be excellent. Why did I ever sell that car ?

My 411 is currently at the local garage having work done on the new air conditioning system so I cant post a photo.

[Kevin H]

Originally Posted by peter dowdle

.... Is it possible to get another photo taken a little further back to help me trace the white wires to there source.

Peter,
I have attached a wider photo, but I don't think it will help - it's very hard to see where the white wires go. Also, to complicate things, my car has had some re-wiring done to incorporate some relays and additional fuses, which you can't see in this photo.

However, I have had a look at the wiring diagrams on this site under Resources. There are a lot of "white" wires and although I haven't checked every one, assuming the wiring colours are formulaic, I suspect that all white wires go back to the ignition switch (which is far from ideal!).

If you look in the bottom left had corner of this diagram Resources - Bristol Cars - Owners and Enthusiasts Forum you will see the symbol which Bristol use for a fuse, labelled A3-A4 and attached to terminal 3 is a white wire going to the ignition switch.

I'm just guessing here, but perhaps the fuse boxes are A and B, and the fuses in each are 1-2, 3-4, 5-6, & 7-8.

PS. The brake boosters have been removed from my car, hence the bolt in the vacuum hose and the plastic bags over the ends of the hydraulic brake pipes.

[PEU186F]

Peter,

My apologies in advance, you are probably going to steam gently when you read this, but by far the easiest and surest way of knowing which fuse feeds what is by removing the fuses one by one and checking out what doesn’t work when that particular fuse is removed. To understand where I’m coming from put yourself in the position of the chap wiring up your car who will have been faced with a load of white wires and a load of green wires coming out of the harness at roughly the same point, also a load of brown and purple wires for the other fuse box. It matters not a jot to him which white wire goes where on the fuse box or indeed which green wire, all he’s got to do is get the whites and the greens to the same fuse box, ditto brown and purple, and hey presto it’ll all work. It would have taken him considerably longer to order them to a set pattern.

So, you see, not even Tony Crook himself necessarily knew which fuse position fed what, which is why it’s not in the handbook. I’m not very good on odds but across two fuse boxes aren’t the odds of your car not being the same as any other in the order of 2 x 4x3x2x1 : 1

When you’ve worked out what’s what write it down, laminate it and stick it up somewhere in the bay - it can save an awful lot of time on the side of the road!

Much easier on a 410, there are essentially only two main fuses and if the petrol gauge drops to zero and the indicators don’t work at the same time, well that’s one of them!

As for all the white wires. I’m only familiar with a 410s wiring but standard wiring practise (was) for white to be used for all circuits that are to be live when the ignition is on. There are at most two lucar terminals off the back of the ignition switch when it is in this position and I counted at least nine feeds on the 410 to all the individual things that need to be on, or available to be switched on, when the ignition is on. Some of these are fused, hence your four fuses, but a number are not (or were not, in those days), including the ballast relay, the tachometer and coil, the relay that switched power to the heated rear window (not the heated rear window itself), fuel pump and others, but my photocopy of the 410 wiring diagram gets a bit blurry at that point. Convention was that the fused feeds that were live when the ignition is on were green, but the unfused feeds were white. But with only one “spare” lucar on the back of the ignition switch the only obvious point to take all the unfused feeds to their various destinations is from the live or input side of the fuse box. There are plenty of lucar connectors at that point. Which accounts for all the white wires, only one will be “in”, the rest will be “out”. How are all the ins and outs connected? I’m pretty certain, but can’t actually swear to it, that there will be a strap between some or all of the “ins” within, ie on the back of, the fuse box.

I realise this doesn’t resolve your meltdown, but I hope it may provide some useful insights.

But as far as the meltdown is concerned my advice, for what it’s worth, based on Morris Minor experience, is to leave well alone if everything works. The insulation is still likely to be ok, but brittle, so fiddling with it is the worst thing you can do, and even if there is a short within it between white and white that really isn’t a problem. If there were a short to any other group of circuits there are likely to be all sorts of odd effects, which you don’t mention so presumably that’s ok too. The only other route out of it is a new wiring harness, which I would not fancy.

My regards

Roger

[peter dowdle]

Thanks everyone for your help. I agree it wont be that hard to sort out which fuse serves which circuits but as mentioned its likely that all the white wires arnt power in circuits but simply a means of hooking into the ignition circuit.

I have just collected the car and will now commence the task of trying to work out where the white wires come from or go to.

Thanks again

[PEU186F]

Peter

While thinking things over you might also like to contemplate the total current that is being carried from the ignition switch on the white “in” wire. Think steady current but remember the switch on condition, particularly into inductive circuits such as motors where the surge current on switch on equates to the stall current, and marvel that the poor little ignition switch has survived for as long as it has. Switching off a dc inductive circuit also brings a host of potential nasties in terms of arcing across the switch contacts.

The use of a very heavy duty relay, sometimes called a contactor, actuated by the ignition switch, but switching current directly from the battery, e.g. from a big brown circuit, might come to mind.

My experience has been that an overloaded ignition switch fails relatively gracefully, initially by introducing a very short hiccup into ones stately progress rather akin to a very short misfire, then the hiccups get more frequent and eventually the whole thing comes to a halt for five minutes or so in apparently mysterious circumstances. And then goes again for a bit after the switch has cooled down. And then comes to a halt again.

My regards

Roger