I'm trying to plan the wiring for my wipers - standard Mini 2-speed unit made by Lucas.

If I read the bumph written by the suppliers of thinwall cable, I should be using 2mm^2, 25A cable. However, every Haynes manual I've looked at this evening (I have a few!) shows an 8A or 10A fuse in situations where it is connected to just the front wiper. The only cars with bigger fuses are where that fuse is connected to several devices. This suggests that 1mm^2 16.5A cable should be more than adequate - and would be much thinner and easier to add to my existing loom.

I've been trying to find technical data to tell me the current taken by a Lucas wiper. The only thing I can find is a Lucas service manual, which states that the current draw should not exceed 4A - if it does, then there's a fault, e.g. something mechanical dragging or sticking.

Does anyone know the typical current draw of a Lucas wiper? (Is Steve from SVC around? )

UPDATE

Just found a Lucas website that quoted the current taken by their 17W wiper motor sweeping a wet screen (with a mechanically sound transmission, I guess):

Low speed = 1.5A
High speed = 2.5A

So why on earth do the suppliers recommend 25A cable?

(And I do realise that motors take extra current at startup... but surely not that much more... )



[Edited on 9/12/09 by David Jenkins]

Start up current might be a lot higher than when it's running all the time.... It could be very high, measure the DC resistance of the motor with a DVM, then calculate the current assuming ohms law, this should be approximately the start up current.. Also remember it must start or it is likely the motor will burn out, so to much voltage drop in the cable plus more mechanical resistance than ideal you might burn out the motor.

Dan

[Edited on 10/12/09 by Bluemoon]

[Edited on 10/12/09 by Bluemoon]

Actually - on the train this evening I realised that I don't have a problem!

The Sierra switch is probably not rated for directly switching the wiper (or I am unsure, anyway), and the Ford column switch is not ideal for the task of switching a Lucas 2-speed wiper, so I intend to make a "wiper controller" made up of a couple or three relays. Because I'm using relays, I can use low-rated wire all the way from switch to relays, with just a few inches of thicker wire for the high current links across the relays, and the original wires from the wiper's connector to finish the circuit.