75ZT Community

Have bought this loom from someone on the other side and need some info to where it connects to the main loom

Not sure but probably at the passenger fusebox. You really need to ask the person who removed the wiring from the main harness.

The Bbus is in the plenum, and the wiring runs into the passenger wheelarch through the big grommet, and then there's a breakout that goes up into the plenum. Jack the car up, remove the wheel, remove the wheelarch liner and you'll see it up where the side repeater is.

For the power wash, remove the dashboard, and run the wiring across the car. Through the grommet into the wheelarch, and follows the top of the wing to the front of the car.

You may choose to find your own easier wiring routes, but then the wires won't be the right length.

I was thinking of doing this with my Tourer, with the Wiring from my stripped Saloon, but apparently you have to also change the Alarm from a Horn to a Siren. This was due to the Wiring and Relays - Not sure 100% as it went over my head.

However, I have been toying with the idea that I may run a link from the already fitted Washer pump, to the secondary pump on the Washer Bottle. This should theoretically remove the need for extra wiring / Replacing the Alarm etc.

The only downside is that both Pumps will operate at the same time, instead of at intervals via the ECU (Engine Control Unit) / BCU (Body Control Unit) etc - I think the Headlights operate every 4 or 5 Windscreen washes. But for me, that is not a major problem, I can live with that.

Yes, the same relay is used to drive the horn, or the pump. So if you want to use the pump you have to fit a siren, and get it T4 (Testbook version 4.Computer Diagnostic System) coded.

If you connect the headlamp pump to the wash pump it will just blow the fuse. The powerwash pump may not look much but the fuse for it is 30 A. You could use a relay to get around this though.

Also, as well as the number of times it operates, it's the length of time. The powerwash runs in a very short burst. You will empty your wash bottle very quickly.

I'll have a look around to see if there's such a thing as a a timer relay that might do the job.

Duncan wrote:Yes, the same relay is used to drive the horn, or the pump. So if you want to use the pump you have to fit a siren, and get it T4 coded.

If you connect the headlamp pump to the wash pump it will just blow the fuse. The powerwash pump may not look much but the fuse for it is 30 A. You could use a relay to get around this though.

Also, as well as the number of times it operates, it's the length of time. The powerwash runs in a very short burst. You will empty your wash bottle very quickly.

I'll have a look around to see if there's such a thing as a a timer relay that might do the job.

Looking at the Haynes Wiring schematic, it appears that the Headlamp washers are linked to the Light Switch Module too, so the Washers only operate with the Lights on.

The wiring is also connected to the "K" Bus and Body Control Unit. I guess there isn't a simple way to wire this in, as from what I have seen, Cars with the Horn Alarm don't carry the loom for the Headlamp washers - So they need the Siren fitting and then wiring routing through for the Washer pump to all the necessary places. Unless I am overthinking this and the Horn alarm Plug and wiring is actually the same as the Washer pump wiring? The Plugs look similar from what I recall, but not 100%. If this is the case though, it would be a simple rerouting of that wiring along with a T4 session to reprogram the BCU / ECU.

I am thinking too that the Volumetric alarm also means I will have issues wiring in my Dimming Mirror. But haven't looked into that yet as really don't fancy pulling off the Headlining right now :p

All wired up, thanks for the advice guys much appreciated. With some help from your selves and my wiring diagrams i have it sorted. Just need a T4 session to sort it out