Club 80-90 Forums

Car Radio auto switching Relay Mod

Have you ever parked up while camping etc switched on the radio and the next day had a flat battery???
Have you ever forgot to switch over the battery switch or forgot witch way the switch goes for which battery??

Then this Mod is for you!


This mod consists of

SPDT Relay : (Single Pole Double Throw Relay) consist of a coil (terminals 85 & 86), 1 common terminal (30), 1 normally closed terminal (87a),
and one normally open terminal (87)

In my diagram When the coil of an SPDT relay is at rest (not energized), the terminal from radio + (30) and terminal from leisure battery + (87a)
are connected together. When the coil is energized, the terminal from radio + (30) and the terminal from engine battery (87) are connected instead.

So when the ignition is off the radio takes power from the leisure battery, When the ignition is switched on (engine Running)
the radio takes power from the engine battery.

Reasons for wiring the radio in this way!

1 When the engine is off the radio takes power from the leisure battery only automatically (apart from the memory (Yellow Wire) but takes very little power)
2 No switches to forget to switch
3 No Holes to drill
4 The Leisure battery can be removed in winter and the radio can still be used while the ignition is on (engine running)

Things you will need

1x Single Pole Double Throw Relay 30amp automotive relay will do fine
2x 15 Amp Blade Fuses ( or equivalent depending on the power draw of the radio please see manufactures specifications)
2x fuse holders or (equivalent mod please see below)
5x insulated female spade terminal connectors 6.3mm
2x scotch locks if needed to connect the radio yellow wire (memory permanent feed) to 12v + engine battery. Also to connect the relay to the switched feed (86)from ignition.
A couple of meters of wire heavy enough gauge to power the radio.

jpeg[/attachment]
Good luck and don't forget to disconnect the batteries before doing any electrical work also use FUSES!!

If you can not obtain an in-line fuse holder you can cut the wire put on 2 insulated 6.3mm female spade terminal connectors and put a standard blade fuse in-line no excuse for not using Fuses please see figure 2. but i do not a recommend this way of doing fuses.
[attachment=1]fuse holder.

Please can this mod be put on the wiki ??

Sorry to dis this you have spent a bit of time getting the diagram together etc.
Most people wire it direct to the leisure, end of. Seems a lot of faff for not much benefit.

Have you ever parked up while camping etc switched on the radio and the next day had a flat battery???

No, I wire it to a leisure battery that is disconnected from the driving battery by a relay when parked up.

2x scotch locks if needed to connect the radio yellow wire (memory permanent feed) to 12v + engine battery. Also to connect the relay to the switched feed (86)from ignition.

Scotch locks notorious for causing problems in wiring.

Sorry mate....can't really see the point.
If you have two batteries (one starter and one leisure) then surely you have a split charge relay wired in, then carry out the well documented and simple radio/interior light mod. This ensures all leisure circuits including radio/interior light and all camping anchillaries, run from the leisure battery only, with the engine turned off.
When the vehicle is running, both batteries (starter and leisure) are joined...as there is no draw on the starter battery there is never any worry about it going flat..simple.

Look at the bigger picture....it isn't 'just' the radio that can flatten the starter battery...

Martin

Hacksawbob wrote:Sorry to dis this you have spent a bit of time getting the diagram together etc.
Most people wire it direct to the leisure, end of. Seems a lot of faff for not much benefit.

I for one remove the leisure battery from my camper in winter and keep it in the warm but still use the van as a daily drive to work therefore no radio in winter.end of??

2x scotch locks if needed to connect the radio yellow wire (memory permanent feed) to 12v + engine battery. Also to connect the relay to the switched feed (86)from ignition.

Scotch locks notorious for causing problems in wiring.

I agree scotch locks can be a fuss i only mentioned then as an option for ease of connection i agree other options are available and work much better!!

If its not good enough for the wiki thats fine its just another option over the switch mod already on the wiki!!

crazytunes1 wrote:Please can this mod be put on the wiki ??

It is as I did this and had it added a few years ago!

Matt had this on his first van I think