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Considering a new wiring harness for your Imp, nothing to fear !

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  • Considering a new wiring harness for your Imp, nothing to fear !

    I have had now 2 requests in the last week as regards making wiring harnesses for the Imp so I have made some notes for anyone looking to do this.

    As regards me manufacturing harnesses unfortunately there is not enough return on such jobs to make it viable for me to make harnesses when Autosparks have looms available ready to drop in.

    Autosparks will customise your loom on request, add fuses and anything other controls you wish, but you need to consider every little detail of what you will have on the car first and just as important, WHERE these will be..

    First, what type of Imp do you have, Imp Saloons basically came in a few basic flavours

    Binnacle Dash

    Covers most models with exception of

    Models fitted with a temp guage, these have an extra wire (Green/Blue stripe) for the temp sender mounted in the thermostat end of the cylinder head.

    This confuses a lot of people who try and retrofit a temp gauges as there is no actual wiring for this and the wire colours in the engine bay for the oil pressure switch and the temperature switch (NOT sender) are the same (White/Blue stripe) and looped from one to another.

    Same issue exists on later PCB style dash binnacles.

    Ammeter Guage wiring, thick brown and requires longer wires from rear of car and then back to ignition switch. And of course backlight

    Voltmeter Wiring, very straightforward but again, it is extended wiring from a standard loom. Again also needs backlight

    That covers "standard" options when ordering, you really do not want to start modifying a bought in loom.

    PCB Style (Round Clocks Dash)

    I must admit to having limited experience on these, the later "Chrysler" cars have little interest for me.

    Main differences here are the indicator staclk wich is on a multi plug and different from early "rootes" cars n that the cancel is mechanical, rootes cars had electrical hold on.

    Same comments on temp senders except the dash connections are on a multi plug and not quite as easy to add into.

    One option on later cars was the heated rear screen, so you have an extra switch and visual indicator for this on teh dash as well as an extra wire to the rear hatch.

    Make sure if you order a loom you specify all your options correctly and especially early/late car.

    Now onto modifications, again location, location, location as you need to jump out the main loom and back.

    You could add these seperately but why spend hundreds of pounds and then add bits to it !

    Electric Fuel Pump considerations

    Push pump at front or pull pump at rear.
    Requires safety relay to ensure the pump cuts out if the engine is not running.
    On the Imp I use the ignition lamp or the oil pressure lamp
    On BMW the ECU handles this as long as the pump is controlled by the ECU (needed for priming)
    Either need an inertia cutout switch as well.

    This is a lot easier than it sounds but needs its place in the harness.

    Additional lighting

    Spot lamps, relays needed and I usually add a seperate fused feed for these from battery
    Fog lamps, fit relay at back and just thin wire for coil rather than run power to front of car and back
    Reverse lamps, needs extra wires and a switch kit
    High level stop lamp (highly recommended) as very few moderns can see ow to ground and always drive a metre off your bumper to get a look !

    Heated Screens

    Front Heated Screen, needs dedicated feed and fuse from battery as well as a timer relay (like a modern)
    Rear Heated Screen, needs dedicated feed and fuse from battery as well as a timer relay (like a modern)

    Additional Controls

    Hazard Lights - an easy option on binnacle cars, but quite intrusive on later PCB style dash cars

    Alternator requirements

    Add up all the potential simultaneous demand from above and you end up looking for a beefy alternator which will reflect cable sizes to that area.

    Standard ACR types only have your power and ignition lamp wires, while Denso style ones also require a switched ignition feed to energise them inirtially. The latter has far higher outputs.

    A full kit, designed by Dave Lane Dave Lane is available from Daves Employers Carwood Brise and can be found here,

    Higher output alternators are available. Price on request.

    If you look at Daves build for his MK 1 SInger Chamois HERE

    After all the wiring fixes, mods, bodges, screwups,DIY madness I have seen in imps I went a little overboard on our won car DDG220C.

    The wiring on DDG has been designed modular like a modern and has provision for upgrade to EFI built in.

    Extras added on DDG
    • Spotlights
    • Extra temp gauge (two senders at head)
    • Electric Oil pressure Guage (as I hate the nylon pipe or should i say it hates me)
    • Tachometer
    • Electric Bonnet opening (I know )
    • Electric front mount fuel pump
    • Fog lamp
    • Reverse lamp
    • Heated front screen
    • Heated rear screen
    • The heated screens can only be on one at a time as 44A would be needed for both on at same time and I have timed them at 10 minutes.
    • Electric washers
    • Voltmeter
    • High level brake light
    • Rear courtesy light
    • Battery conditioner/aux power in/out
    Sounds a lot of work, actually it isn't

    All that runs from front of the car to rear is.

    13 core trailer cable (5 x 2.5mm csa and 7 1.5mm CSA)
    2 x 8.5mm CSA feeds.
    1 x 6.0mm CSA fro front heated screen.

    Trailer cable ran on left hand side of car, higher current on right side of car, both ran at floor level and NOT in same channel as heater hose, it is considered bad practice by me to run any cabling beside a heat source and of course the wiring capcity needs de-rated.

    Rear wiring including the AUX power socket which I use to trickle charge the battery when stored. This has been modified already for second temp sender and high level brake light

    Click image for larger version  Name:	ddg-early-rear.jpg Size:	341.6 KB ID:	18408

    All "heavy" power work needed for rear of the car is done at the rear (point of load) and fused seperately, it looks incredibly complex at first glance but this is the rear "module" tucked into the rear parecel shelf behind the solenoid.

    Click image for larger version  Name:	20200401_210143f.jpg Size:	448.8 KB ID:	18409 Click image for larger version  Name:	20200331_221320.jpg Size:	3.27 MB ID:	18410

    I am happy to help out anyone local (time permitting)

    If you are in the midlands or near Manchester you also have Mike Dent aka moose moose549 on your doorstep almost and Mikes wiring work is awesome.

    Around that area for any wiring work it would be worth giving Mike a call for a quote

    Last edited by John A. Ross; 27 February 2022, 11:35 AM.
    / John