Electrical questions

[Chuey]

What is the substance that I'm supposed to smear between the electronic gizmo under the tank. That is, the part that sits on top of the brake splitter. I have dielectric grease. Is that what I use?

Second question: When hooking up my wiring for the voltmeter and clock, I've figured out some of it, but I would like to know where, in the headlight bucket, do I connect the red wire for the voltmeter?

Third question: The wires for the lamps in the clock/voltmeter connect to what in the bucket?

Chuey

[chasbmw]

I use heat sink paste, available from any computer store, usually used between the top of a CPU and the heat sink.
Charles

[Kurt in S.A.]

Also at Radio Shack.

Kurt in S.A.

[ME 109]

Also need to know the ideal preparation of the mating surfaces for the heat paste?

[Kurt in S.A.]

Also need to know the ideal preparation of the mating surfaces for the heat paste?

Follow the directions on the package???

Kurt in S.A.

[ME 109]

BINGO!

[dougie]

Also need to know the ideal preparation of the mating surfaces for the heat paste?

Clean.

[Chuey]

Thanks, I've cleaned the surfaces and in fact, flattened the top of the aluminum plate.

Any ideas where I should connect those two wires I asked about?

Chuey

[vanzen]

Also need to know the ideal preparation of the mating surfaces for the heat paste?

Thermal paste is designed to enhance thermal conductivity between the ICU and the frame
as a way to disperse the heat generated by the electronics into a "heat sink"
(an object that transfers thermal energy from a higher temperature
to a lower temperature fluid medium, air in this case)
and thereby moderate the ICU's temperature.

Clean, dry, and free of corrosion works - the paste will do the rest.

Looking at my schematic for a pre - '81 /7 & S –
There is no red wire to or from the voltmeter ...
A red wire is shown at the clock to #30 on the H-bucket fuse panel.
Both clock & v-meter lamp wires are shown heading to one of the two 8A fuses in the H-bucket panel.

RS was wired different, still no red wire to / from the voltmeter ...

[Rob Frankham]

What is the substance that I'm supposed to smear between the electronic gizmo under the tank. That is, the part that sits on top of the brake splitter. I have dielectric grease. Is that what I use?

Second question: When hooking up my wiring for the voltmeter and clock, I've figured out some of it, but I would like to know where, in the headlight bucket, do I connect the red wire for the voltmeter?

Third question: The wires for the lamps in the clock/voltmeter connect to what in the bucket?

Chuey

I'm working with insufficient information really, yes, you say you are hooking up a voltmeter and a clock but are they stock BMW items... I'm assuming not and, do you have the stock wiring loom for a BMW voltmeter/clock... again, I'm assuming not. The best thing, I guess, would be to try and set out all of the connections and where they should connect to.

Clock

The clock will have two connections. One will be negative and that should go to ground. The other will be positive and that should go to an unswitched supply, which, on airheads, will be a red wire or a red terminal on the board in the bucket.

Voltmeter

This will also have two connections. One will be negative and should go to ground. The other will be positive and should go to a switched supply. On the stock airhead setup this will be a green wire or a green terminal on the board in the bucket.

That being said, IMHO this is not a good layout since it means that the voltmeter will be affected by any voltage drops in the system and may not show the true battery voltage. If you want a more accurate instrument
(Note I don't say 'accurate, just 'more accurate', automotive voltmeters are not renowned for being precision instruments) I would advocate arranging a supply direct from the battery. You'll find my reasoning and a practical circuit here http://robfrankham.co.uk/bike/external_circuits.htm

Lights

Both instruments will have at least one light and each bulb will have two connections.

One connection will be to ground (In some cases, this ground connection may be shared with the instrument ground connection). In many cases, this ground will be connected to the metal body of the lamp holder and, if the body of the instrument is also metal, this may well be connected to the instrument ground, it is very important to ensure that you identify the lamp ground correctly or else you will be creating a direct short circuit as soon as you switch the lights on . On the lamp holders in the BMW loom, the lamp ground (and all the other grounds for that matter) will be brown but on aftermarket wiring it could be black or green. If your not sure make sure. If you don't know how, find someone who does.

The second wire to the lamps is the positive feed. It needs to go to a wire that is live when (and only when) the sidelights (parking lights) are switched on. This will be a Grey/Black wire or a Grey/Black terminal on the board in the bucket.

Hope that helps

Rob