Hey Doug, you mentioned hooking up the kickdown to the full load switch. Makes great sense! It appears very easy, but you mention relays. Im a very basic moron with relays, can you clarify this mod?

 

Oh, yes please!

 

It's pretty easy. Just a little wiring modification. It'll give you kickdown at about 3/4 throttle rather than having to absolutely bury your foot into the carpet.

You just need some 16 gauge wire, some crimp-on terminals, cutters/crimpers, and a generic 'Bosch style' accessory relay with the typical 30-85-86-87 terminal designations....as used for radios, fog lights, etc.

Remove wires from kickdown switch

Green/white wire from kickdown switch goes to terminal 30 of the relay. This wires is for the kickdown solenoid itself.

Green wire from kick down switch, , which is 'key on' 12v, goes to terminal 87 and terminal 86...so you'll have to make a little loop

Locate the white/slate wire at the full load switch on the throttle turntable. Splice into this wire (or use a piggy back connector) with a new piece of wire, the other end of which goes to terminal 85 of the relay

The control side of the relay (85 and 86) gets voltage from the green wire and is 'triggered' by the ground signal of the white/slate wire when the full load switch closes.

When the relay is triggered the contacts on the the 'load side' (87 and 30) of the relay close, so voltage from the green wire goes to the green/white wire...which activates the kickdown solenoid in the trans

Location of the relay is your choice

The now-abandoned kickdown switch can be used as a full throttle a/c compressor cutout. If interested I'll explain the wiring


Cheers
DD

 

Explain!

 

USA spec cars have TWO full throttle switch devices. These protect the engine form going too lean at WOT (I believe). On UK spec cars there is only the (lack of) vac-triggered device, which is the brown thing on the cabin end of the A bank manifold. When at WOT (so no vac) this makes a connection to earth which effectively over-rides the throttle potentiometer and ensures the ECU goes to full fuelling.

On USA spec cars, this device is supplemented by a microswitch on the throttle capstan which also has the same function. I do not know why there were two such (effectively working in parallel) devices on the US spec cars. It is this capstan switch that can be double wired to also perform the funtion of the kickdown switch, replacing the one on the throttle cable and so giving kickdown at a smaller throttle opening.

Greg

 

Right!


I've often wondered about that




Exactly right, and that's why I mentioned

"Locate the white/slate wire at the full load switch on the throttle turntable."


Cheers
DD

 

This will work for (at least) 1988 and older V12s. There are some variations in a/c compressor wiring for different years. You're simply adding a relay to interrupt the existing compressor circuit.

You'll need a accessory relay with 30-85-86-87-87A designations. Very common. It's 'switchover relay'.

Locate black ground wire at existing a/c compressor relay. Cut the wire.

One end of the cut wire goes to term 30 of your new relay and the other goes to term 87A

Term 85 of the new relay gets 12v "key on" power
Term 86 of the new relay is wired to one side of the kickdown switch.
Term 87 is left empty.

The other side of the kickdown switch is wired to a good ground/earth

Under normal throttle openings the compressor circuit is not interrupted. The ground circuit for the existing a/c relay is intact via terminals 30 and 87A of your new relay.

At WOT the kickdown switch closes and this triggers the new relay. The relay contacts flip from 30-87A to 30-87. Since '87' is empty there is no longer a ground/earth for the existing a/c compressor relay...so the existing a/c compressor relay de-energizes and the compressor is turned off.

Cheers
DD

 

Geniuses! Thank you both so much!

 

This is a great post!! A special thanks to Doug & Greg!! I've been learning a lot on this forum!!!