Best wire splicing method.

Brazed seam funnel entry connecters made by AMP or Molex with bonded nylon sleeve. & then you need to crimp them with the right crimp tool. By which point you're spending >£0.50 on every buttcrimp. The heatshrink duraseal ones work very well.

If you're solderings up to it & you clean the flux off before the heatshrink it works well. It's tricky to solder wires over 2.5mm2 without heat damaging the insulation.

I dislike the look of those insulated red blue and yellow crimp connectors and reckon they're not that tolerant of stranded cable at the lower end of the sizes they're said to accept. And I do have a decent crimp tool.

I prefer standard non insulated lucar connectors from the likes of Vehicle Wiring Products with the use of their crimp tool. Which is sadly rather expensive. However, crimping lightly with pliers then soldering is ok too

- although not so strong mechanically.

The smaller ones definitely work better, red butts are the right size form most things on cars but blues seem to be the most commonly used.

Standard practise on internal and protected external(ie under bonnet) wiring is to trim back the insulation on the wire you're splicing into, and solder the extra wire on. Then wrap up with some good quality black tape (cut off an inch strip, then stretch slightly as you wind it around). For exposed external wiring (ie under vehicle), it's better to cut the wire slide on a bit heat shrink, solder the wires together, and shrink the heat shrink over. Anything I do, I normally put a bit silicon contact grease over the soldered bit, before shrinking the heat shrink on.

Having tried most types of connector on motorbikes years ago, I wouldn't entertain ANY soldered connections in exposed or semi-exposed areas, crimped spades are the best out of easy to get connectors but an added layer of heatshrink sleeving would be ideal for exposed areas. Soldered connections rot in months due to electrolysis and would depend too much on heatshrink/grease for protection, but should be fine in the driver's side of the bulkhead.

Thanks for all the feedback.

Because this new alarm is quite a large, flat box and I don't have a large enough flat metal panel under the bonnet to mount it I think the alarm is going up under the dashboard so it will be in a nice dry enviroment.

Now I have a new problem. The old alarm had an seperate box of tricks to first lock and then deadlock the doors. A feature I'd like to keep.

When I apply an earth to the input of this extra box, one relay closes and sends voltage to the cars central locking module to lock the doors, followed by a second relay to deadlock the doors. Voltage is arriving at the central locking module on both wires but no locks are operating. I know this used to work with the old alarm. It was only disconnected because it started to give false alarms and I have neighbours. Doors lock and deadlock normally with the key.

Ah well, tomorrow back to lying upside down with my head under the dashboard although I don't quite know where I'm going to go from here.

(It's a BMW 318i if anybody has any ideas on this).

Thanks again, Nige

Hold fire on this one. I might just be a dumb plonker. I was only checking with light bulb to earth probe type thing and I think it wan't very bright. The earth from the original alarm wasn't connected and I reckon I was getting a low voltage due to it finding an earth via a relay coil or something. Back out there with a meter right now.

Nige

My oh so expensive lucar crimper isn't a ratchet type. It's a cantilever design. Makes no difference how you get the required pressure.

Cancel everything. It needs the door lock switch to be operated and then everything works. Now if only I could find my solder. :-) Nige

I don't think any of the hideously expensive collection of crimpers I own (unless you count the hydraulic ones) use the ratchet mechanism to increase the force, they're all over centre lever systems. Ratchets are just to make people squeeze them far enough.