Wiring an Imp modern car style Part 1 - engine bay fuses

[John A. Ross]

Wiring an Imp modern car style Part 1

Ok, one of the Imps weakest points is the wiring, primarily the wiring, on top of being 50 + years old in many cases it was IMHO never up to the job. What we want to fit is this.



Which is as I posted before as a drawing, sometimes it helps to relate the picture images (theory) to the real world. I have not crimped any of those connections as this is just a dummy but bear in mind that is an essential part to get right.

As you can see there is PLENTY space above the battery with the RB340 box removed. This is the space left when nothing is in there.



And size comparison what will be fitted to RB340



This first part of the 8 articles covers how i will be adding fuses into the engine bay of DDG220C (see restoration stories) which I am currently restoring and wiring is up next and is an evolution over JDL889F (again see restoration stories) .

So thought I would share the thinking up front in snippets as the ideas can easilly be applied on a case by case basis to standard imp wiring in places of the RB.

The wiring assumes an alternator which is really a must have update.

From the battery terminal we enter the fuse box using 25mm csa cable into a 25-8 crimped spade. (25mm ca sa - 8mm hole = 25-8 ) .

These connections need a solid crimp, hand crimps rarely do it and a hydraulic crimp tool tends to be needed, you can buy these leads ready made from many sources cheaply.

From the other side of that main fuse there is another lead from a 25-8 crimp using 25mm csa cable to another 25-8 crimp which terminates on the solenoid. Again ready available
made up.

That leaves 4 sub fuses, although I show 4 x 40A fuses these should be rated to suit what they are supplying



This section matches up to the schematic drawings that will feature in the final article towards end of February




Mounting wise a couple of rivnuts can mount the fuse box itself in same space as the TB340 box was fitted.

For anyone that wants to mod a standard imp, the process is pretty similar, the brown wire that supplies the car comes out the loom from the rear inner wing, you likely still have this thick brown wire connected to the RB340 box and another thick brown wire connected to the terminal beside it, this is just a short jumper wire to the solenoid take off (big 6.3mm spade). You really want to unwrap the wiring and remove that brown link wire as you will not need it.

On the standard Imp you will more or less be using only the main fuse and two secondary fuses one from your alternator feed and one to the thick brown wire heading into the inner wing. Conside the other two spares (or for spotlights, heated screens etc.)

What does this cost, to make things easy I have pulled prices from Car Builder Solutions

1 x Fuse Holder Part Number: MFDB4 Cost £24.00
1 x 150 Amp Mega Fuse Part Number: -------- Cost £ 3.00
4 x 40 Amp Midi Fuse Part Number: MIDV40 Cost £ 2.16 each total £8.64
3 x 25-8 Crimp terminals Part Number: RT8 Cost £ 0.60 each total £1.80
4 x 10-6 Crimp terminals Part Number: -------- Cost £ 0.60 each total £2.40
1 x 1M Length Red 25mmCSA Cable Part Number: BCR Cost £7.20

Total budget assuming you re-use your existing battery terminal is £41.00 approximately

Seems expensive but other than a couple of cheaper fuse boxes, relays and wire, thats the main heavy items sorted.

Makes short work of a BMW rewire as well !!

First introduction done, more actual pictures to follow

Tomorrow nights updates will be a suggestion for Heated Rear Screen installation (HRW) using illuminated switch and relay.

Colimp66
The Diggerboy

[John A. Ross]

Similar solution as used on a BMW Engine conversion

Spot the fuse box and solenoid wired exactly as I would do it in an Imp

[John A. Ross]

And here is an earlier evolution in my green chammy.

In this instance I used one mega fuse holder on its own but wired up the same, then two seperate midi fuses and holders for live and switched 12V feeds

This one did not have the alternator fused. That one evolved after I seen an alternator wire chewed up and melt the cables !




This is very close to standard Imp wiring and can be done for about 1/2 the price of what is above. However you have to make up more "tails" and the flow battery to loom is not as nice.

[Dave Lane]

Looks really neat , great how we do the same thing in a different way

[John A. Ross]

Dave, yes george was pretty simple, keeps it neat but just shifted some high AAA fuses into a small fuse box inside the bonnet area, so still had this power to front, power to back (example brake lights) on thin"ish" cable, lights were 10% brighter on the light meter if fed direct from battery at back compared to back of car, to front for fuse to back, switch and then lamps.

This time round the fuse for things like coil, brake lights, fog, reverse are all at back.so small 6 way fuse box and a few relays at back, then it does not matter about power from front as the drop in voltage on signal wires to trigger rlay can drop to 7~8V and still work fine.

Changed a few cars positive to negative earth today including our MK 1 as we wanted to put a few guages in, excluding the horn and heater wirse fuse I will stick that up later just to show folks how easy it is.

Except getting my big hands round back to field terminal that is !

- John