Roverlike

I would suspect your switch. How often do you open passenger window? I would say that contacts on the switch might be dirty.

Actualy yes. Horns on models with two horns use same ground and power wire, so splicing is fine.

I made some tutorials on this topics if they might help you:

1. forums.mg-rover.org/mgf-mgtf-12/mg-f-tf-...ection-guide-866231/

2. forums.mg-rover.org/mgf-mgtf-12/mg-f-tf-...elay-listing-487819/

Anyhow, if you are missing corresponding wire colours from the car (as it seems to me on your picture), the you might want to strip isolating tape around wires deeper in the engine compartment as somwhere there previous owner must joined these new wires to old ones, and there you can find colour wire match.

Dark Ice Design created Red dipstic top, see here: www.ebay.co.uk/itm/Universal-CNC-Alumini...5gok9kZce1EODTdXi2fQ

Not sure that you have earth or live which are active only when alarm is disarmed. Alarm is not working in that way.

G0RSQ wrote: This applies to TF with electronic odometer only.

As far as I am aware the odometer reading is stored in at least two places on the car. I believe in the odometer itself and also the ECU. (I replaced my ECU and got a higher odometer reading, which messed up my limited mileage policy!)

Replacing either will result in the HIGHEST value stored being used, and set in the odometer display.

If you install a speedometer from a lower mileage car, then the mileage stored in the ECU will be used. If the odometer has a higher reading than the ECU, then the odometer reading will be used.

After this both stored values are syncronised.

So I believe if the new odometer has a lower reading, the stored value in the ECU will be displayed.

However not sure how this will impact when changing a KM odometer with an MPH ECU!

This must be for TFs made after 2005, as none prior to this stored mileage anywhere else then on instrument itself.

To be able to get to the sensor you need to remove t-bar. Problem is, in order to remove t-bar, you need to remove both seats.

Seems to me that might be microwave sensor that is not working correctly, either because it is faulty or plug to it does not have proper connection (corrosion on the terminals etc).
There is no other motion sensor then microwave one.

Have you tried same experiment but locking the car only with the key, while sun is still up? If locked only with the key and no response on tugging, then, I would say microwave sensor is the culprit.