Mustang S197 Light Conversion Relays
The relays you need are low current devices. Do not use standard ‘automotive’ style relays. The average Automotive relay has a coil resistance of about 60-90 Ohms, where as a relay more suitable, will have a value of about 1000 Ohms. You really do need to put a back EMF protection diode across ANY relay coil connected to an ‘electronic’ output. This will minimize the back EMF voltage across the SJB outputs. More on that on the diode article.
Advice from the Mustang forums recommended one type of relay made by Omron. I have tried others but the Omron ones are as cheap as any other and ideal for the purpose, so lets go with those.
You can get them from anywwhere using the Omron numbers below. I get mine from here.
The relays themselves are Omron G2R1SN24DC(S). The RS Online number is 353-821. They look like this:
They plug into some special bases, which are also available from RS Online – they look like this:
The Omron number is P2RF05E, the RS Online number is 353-944. Having plugged the relays into the bases, they slide on a metal rail in order that they can be fixed in the boot where you will site them. RS Online also stocks this, it is called DIN rail, and the RS Online number is: 424-131. That stuff looks like this:
When you come to wire up the relays, remember to fit your EMF protection diodes – this is critical. The relays have five terminals on the bases, this is how they wire up.
The relays are labelled thus:
1 (-)
5 (+)
4 (11)
2 (12)
3 (14)
And they wire up like this:
1 – to earth
3 – the live from the battery.
4 – the new feed to the particular new light in question.
5 – the input from the source light you are tapping from; the switching wire if you like.
2 – redundant in this application.
Therefore, the EMF protection diode goes between 1 and 5, bridging between the only feed from the SJB and ground – with the black end of the diode going to the Nr 1 ground terminal.
