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Electrical System

A dirty engine will always give electricity an alternative path to where it should go. Electrons will always take the easiest route.

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The Haynes manual does not show the late model fused loom
The fusebox has space for four fuses, of which three are used.
The white wires (the two into one and the single lead) all go to the first fuse on the bottom terminals. The wires coming out on the other side are green.
Using the diagram in Tim Millingtons book for cars with alternators the terminal should be 2. There should be 4 wires onto T1 and 4 coming off T2 which is the top and bottom of the same fuse i.e. No.1 which is live only with ignition on.
3 is live all the time and 5 only when the lighting switch is on.
Terminals 1, 3 and 5 are the tops of the fuses (supply voltage), 2, 4 and 6 are the bottoms and load voltage. The only problem is that the wires, none of them, are white on the circuit schematic.

Simon Creasley: I've installed an alternator. This has made a world of difference to my car's charging capabilities. The alternator I fitted went on very easily. I used one from a Hillman Hunter, and this had bolting points which could be easily bolted to with long bolts. I didn't have to move the oil pump on, or rotate the distributor, which everybody had told me I would have to. I have had to use a new fanbelt though since the old one was then too long. The installation was easy, it looks smart and can be returned to original without major surgery. Minor adjustments have to be made to the wiring. If you are interested I will send details of which fan belt you need to use and what wiring changes have to be made.

For crimping the everyday insulated terminal (red, blue and yellow ones.
If you envisage doing any more than the most basic repairs to the Imps' electrics, then a worthwhile investment is a tool called 'ratchet crimper'. This gadget will crimp all coloured terminals properly. It will crimp the conductor part with the correct pressure and without damaging the fine strands of the conductor; it will also crimp the plain sleeve part, which is important as this prevents muck getting in, and it provides strain relief for the incoming cable, too. Expect to pay around the £18 mark. (prices have been coming down.)
Carl Anson, Impressions Dec. 1996

The Imp was fitted with 5¾" Sealed Beam Light units.
7" headlamps (Volvo 140 and many British english older cars) will fit and cost only £10 or so.

Road Vehicles Lighting Regulations, 1989:
Headlights must be properly adjusted to prevent dazzling oncoming traffic and must be used in such a way which would not dazzle or discomfort other road users. This is part of the MoT test.

Four 'Stanley' headlamp units from a Honda Accord (Y reg, perhaps) will fit into the Stiletto bowls and give an increase in light out of any four-eyed Imp (2ndhand for maybe £10 the set).


Halogen lamps give more light because they get hotter. The filament is kept at a temperature of around 3000°C. The bulb itself is somewhere around 600°C. This extra heat is a problem in an ordinary lamp. The reflector in the direct vicinity of the bulb may start to discolour (blueing).

How much and how soon is difficult to say. It depends on how well the back of the reflector transports excess heat; whether or not there is any airflow etc. The wattage doesn't influence the temperature of the bulb, but higher wattage does mean the heat gets spread over a larger area.

I don't think the glass would get damaged, but because of the extra light and because they're built differently, the radiation pattern is different. The pattern in the glass differs; the filaments are located differently and don't match the lens. The radiation pattern would be incorrect.
According to Dutch law it is illegal to put halogen into ordinary lamps, because you might hinder opposing traffic even at dipped beam.

Normal lights have a convex lens; Halogen conversions have flat lenses. Theory: If you put halogen lights in a non-halogen lamp, the reflectors may gradually turn brown and the glass discolours will get hot enough to get damaged by road grit (sand-blasted). This would reduce the light output.
Not sure if the lenses will get as hot as that...

In stead of fitting extra lights when you want to improve your lighting, you may prefer to replace your headlights (perhaps just the outer units on four headlight models).
The standard Imp units can probably be replaced with Halogen light units LUB222 and LUB223 for UK(RHD) use.
Unfortunately, for LHD countries it would require LUB224 in stead of LUB222, and these are no longer available from Lucas. This type of light unit is probably catalogued for Jaguar XJ6/XJ40 1985-95. Cibie or others.
The two lights on the inside:
The two lights on the outside:
as the XJ6
as the XJ40  
H1 bulb
H4 bulb
(rounded lens, like standard Lucas units)
(flat lens, squared off)
Wattage for std. 12v: 60w/55w for the H4/outers, and 55w for the H1/inners (?).
The XJ40 inners might also be worth to look at.
Relevant site: Auto bulb

If you're worried about the wires (they may be 'overrated'), worry about the switches, too. A relay costs only £5 and they may be worth the trouble of fitting them. If you wire up extra lights, you must also fit a relay to prevent the switch from burning out.

Amps = Watts / Volts
Stiletto on mainbeam: 200 Watts / 12 Volts = 17 Amps approx. (which is about all the power of a dynamo.)
Headlight output in Watts
Type Main beam   Dipped beam   Total Main/Dip.
Standard 7" 60 45 120/90
Q. Halogen 7" 60 55 120/110
Standard 5¾" 50 37.5 100/75
Q. Halogen 5¾" 60 55 120/110
Four headlamp Imps have two 50 Watt main beam only units, giving a combined output of 200 Watts on main beam
If you find your dynamo won't cope (while both dynamo and battery are in good condition), then you'll have to change to an alternator.

Headlights for an early Clan
Lucas say that lights from a Citroen Diane could be used, but they don't incorperate the side lights.

Brake lights
Stiletto brake lights are supposed to work with the ignition switch off.

Late cars have the worlds most surreal indicator wiring ever: twist all wires together and cover in molten plastic in a random place.

Lucas indicators on an Escort Mk1 - photo from

The Escort Mk1 uses the same set.

Reversing lights
Fitting reversing lamps to an Imp / Brian Baylis. - Impressions 1990 Spring, pp. 32-34
Caledonians have automatic reversing lights (on an aluminium number plate panel). It has a micro switch (fairly standard).
The Lucas switch had a plunger which was pressed by a plate attached to the gear change shaft. The actual switch was held on by the two rearward vertical bolts, which hold the main gearchange assembly to the body. But everytime the gearchange shaft was removed from the transaxle the switch got broken.
If the switch is in place but the lights aren't, you can easily use the rear turn-indicators as reversing-lamps with a 'gate' network of four Schottky rectifiers. No extra holes required.


Do not fit a plastic replacement pulley. They will have a short life on a high-revving engines. And if they break, there is no drive to the waterpump, leading to overheating.

All Imps with twin headlamps were fitted with a more powerful dynamo C40L. This can be recognized by having an unstepped casing. It is slightly longer, too. The last Imps made were fitted with alternators, not because they had more accessoires, but because by 1976 the general public expected new cars to have them.

G.J Smith describes how to replace the Imp's dynamo and regulator box with a Kucas KA9 36 amp altenator in Impressions January 1988. Includes diagrams and drawings.

Alternator / Dynamo Output
Standard dynamo 22 Amps
Sport/Stiletto dynamo   25 Amps
16 ACR alternator 34 Amps
17 ACR alternator 36 Amps
18 ACR alternator 43 Amps

Battery cables
If the earth lead from the battery to the solenoid is fraying at its connection lugs, you might want to replace it. These cables are quite thick and connectors are not readily available. But most electrical wholesalers stock suitable terminals, called 'copper tube crimp lugs'.
To crimp them, use your wire cutter-cum-stripper-cum-crimper-cum-bolt cropper thingy. It has a large hole near the hinge, usually marked 'ignition terminals'. Now you know what it's for. ;-) Alternatively, the lugs can be soldered with a blowlamp and resin cored or electrical solder. Don't use plumber's solder and flux as the ingredients in the flux mean that you will be repeating the job in a few months. Most electrical wholesalers have these lugs in split bags, and they are ordered by wire diameter and lug hole size. CT35/6 and CT35/8 are the sizes you will most likely need.
Carl Anson, Impressions Dec. 1996
comment by Graham Pearson: This is also useful when you want to shorten overlong cables. Shorter cables mean less electrical resistance and therefore less voltage drop.

Emergency Light
To illuminate your engine bay (in case of an unlikely nightly breakdown) use a map-reading light, the type with a flexible metal 'stalk'. Screwed to the rear cross-member, next to the engine mounting. Clips to the bilkhead near the coil.

Rear window heater
There does not seem to be an official wiring diagram for the rear window heater.
The warning light is on the other side of the dash from the switch.

Wiring loom

It doesn't take long to neatly enclose a bundle of wires in PVCtape, and as well as looking neater the wiring is also more reliable.

Andy Dawson:
The technique I use for making a wiring harness is to lay all the wires along the route that I intend them to take and leave adequate ends so that we can put the relevant connections on after the harness is made. I then tape the leads before and after the junctions of the branches. This way the wires are held together sufficiently for me to bind the PVC tape round the complete bundle.
The reason I leave the individual connections until last, is that you can then get the lengths just right and not have any excess wire floating around.

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