1985xjlaredo said:
Ok here is a drawing of what the diagram on the package looks like
If I were to guess it is displaying that both 87 pis are hot at the same time
Correct.
If it's a 4-pin relay, it's an SPST. The fourth pin (usually pin 87 on DIN relays) is either ON or OFF. Terminals are usually numbered 30-85-86-87.
If it's a five-pin relay, it will be either SPDT or DPST - and you can tell either by the terminal numbering or the diagram that is usually either printed on or moulded into the case.
If the pins are numbered 30-85-86-87-87a, it's an SPDT relay. Pin 87 is OFF and pin 87a is ON, until the relay is tripped (then pin 87 is ON and 87a is OFF.) This type is also called a "changeover" relay, and is probably the most common DIN relay going.
If the pins are numbered 30-85-86-87-87, it's a DPST relay. Pin 87 (both of them) will behave as pin 87 in both other types of relay - you just have two of them.
Wiring conventions:
Pin 30 is the power source - this is the one that gets wired directly from the battery, the alternator, distribution, or whatever. This lead had damn well better be fused going in!
Pin 85 is the "signal" to the relay. This is the one that will come from the low-current switch you're using, be it a toggle, press button, vacuum-actuated, thermal switch, or whatever.
Pin 86 is the ground for the coil - this is the one that goes to a convenient earth terminal somewhere.
Pin 87 & 87a are for the loads. You'll usually use pin 87 for common loads - the idea behind having pin 87 and pin 87a is to provide a "logical OR" for switching back and forth between loads. Pin 87a usually goes unused.
All three relay types may be used as an SPST relay, and you can replace the four-pin relay with either of the five-pin relays, if that's all you have to hand and there are five cavities in the socket (usually the centre one isn't wired.) Check your wiring before you do the swap - and especially check if you want to switch off between the SPDT and DPST relays...
SPST - Single Pole Single Throw. Switches a single circuit either ON or OFF.
DPST - Double Pole Single Throw. Switches two circuits ON or OFF in tandem
SPDT - Single Pole Double Throw. Switches a single circuit between two possible states, as a "one or the other" option ("logical OR.")
The typical DIN relay uses about 100-150mA for the coil, so you can go down to 18AWG handily with wiring for that side. Terminal-side wiring should be sized and fused according to demand (and not necessarily to the relay capacity. You can use wiring suitable for 30A if you think you might use it for something else - then you just switch the fuse for the load you're using. However, the fuse should
always be sized according to actual demand, and not circuit capacity (if you overbuild it.) If you have a power consumer rated for 10A, you can build the circuit for 30A, but the fuse had damn well better be a 10A job...