van radio wiring.

[xpress]

hi. I have four wires going into a connector for the radio


blue and white
red
brown
brown

there is a black earth to the dash too.

can anyone tell me what these are and which one is 12v always on?

[xpress]

also anyone know where i can get t25 radio socket with a length of wiring to fit into this socket?

[Graham81]

A multimeter will unveil the secrets within!

[Mark S]

Red most likely power (always on).

Brown *in my van* is earth. That's not to say that this is the case with your radio wiring, though. Check!

Blue/white is an odd colour. Are you sure it's not one of the speaker cables? Otherwise it could be the ignition signal or an output to an amp/powered aerial.

The black 'earth to dash' doesn't sound right. Does it definitely go to chassis? I would expect this to be ignition signal. Test it with the key on.

Best advice is from Graham: 5 minutes with a multimeter/test bulb should clear it up.

[xpress]

will check with a multi. thanks for the interest. yes, definitely the black is going to a screw on the dash.

there's not actually any speakers wired up at all in the van anywhere, it was a commercial panel. so i guess this plug was just for the electrics on an old style radio and the speaker wire would come out of the car radio.

i wanted to get something to plug into this plug, there's only one that appears to be there, it's early electrics in this van, and on the other end an ISO plug. in this new wiring i am going to run an always on 12v to a cig socket or something.

here.JPG

[Mark S]

Er, OK, then it's probable that:

Red = 12V (always on).
Blue/white = ignition (or other way round).
Black (and maybe also brown) = chassis. I'd say there are two browns because it's part of a loom, with one going to earth and the other on to another component.

If you haven't got an always-on 12V feed, splicing into the cig lighter might not do it as I believe they are also off the ignition in most T25's. Better solution might be to run a decent-gauge wire back to a spare way in the fusebox.

Make sure earth is good as well, otherwise sound quality will suffer. Connect to more than one, if to hand, or run a wire to the multi-way earthing point adjacent to the fuseboard. Scew into dash might not be ideal by itself.

You might be able to find a multi-plug to plug into that socket in Halfords or a car audio retailer. Otherwise you could probably make something up using various sizes of male spade connector (eg: http://www.maplin.co.uk/miniature-male- ... ack-388515" onclick="window.open(this.href);return false;). Personally, I'd do a proper job: cut the old socket off and solder the tails from the new one to the old wiring, sealing with nice heat-shrink wrappers. http://www.maplin.co.uk/heat-shrinkable ... icers-6860" onclick="window.open(this.href);return false;. If you could manage to slide the sleeve over one cable first, then solder the joint, then slide the connector over the solder, cimp it and shrink it, you'd have a bomber connection that will be going nowhere.

[xpress]

thanks for that, i actually didn't think of pushing in some spade connectors that's an idea. apparently i think this connection pictured on here is a din connection, popular in older cars.

also, for a 5v, 1.5amp device what inline fuse rating would you recommend on the end of it before i wire it into a 12v? would a 2 amp fuse be ok or would you use 1amp?

[Mark S]

A 5V, 1.5A device connected to 12V? Do you mean 5W(atts)? If you do mean 5 Volts, you'll more than likely blow it up when you stick 12V across it.

If 5W, that should draw less than half an Amp at 12V, so a 1A fuse ought to cover it easily. If it blows, replace it with a 2A. Most fuses can tolerate current ~50% above their rating in any case.

I'd expect a stereo to use more than 5W, BTW. There's no harm in putting a bigger fuse in provided your wiring is thick enough to handle the current in the event of a short. If the fuse is bigger than the wire, the wiring will burn out first and could cause a fire.

HTH

[xpress]

oh no, this takes in 12v and i am wiring in an adaptor that steps it down to 5v 1.5amp.

[xpress]

are there some spare ways in the fusebox? I have early set up. actually I think there are. I will take a look at how the wiring comes out of these. I guess there might be redundant fuse terminal there but not sure if there will be 12v coming off it. how does wiring attach to this box, is it held with a captive screw and plate like on car audio amps or a spade connector? can anyone explain that a bit more?

[Mark S]

Ah. So on the input side of the converter a 1A fuse should be OK, and if you were putting a fuse in the 5V side it would obviously need to be >1.5 = 2A.

There are some spare ways in the fusebox but it is not always easy to work out what's what. You will obviously first need some spare blade fuses to put in the empty ways, and then do some prodding around down below with a multi to see what voltage appears where. It's quite easy to drop the whole board forward if I recall. This allows you to see what's behind it and gives more clues. Tapping into a spare way is quite easy: you can use a male spade connector in the front of the board once you have identified the right slot. There are normally all sorts of slots for additional relays etc that you can take over. OM might be helpful as well. Is there anything on the Wiki here?