relay draining my battery

Hey everyone, So here is the situation: I have a variety of things in my vehicle that require a switched 12V (ignition power) I was tapping off of a random wire under my dash for a while for just little things. Well I just put in some aftermarket gauges for the engine and I figured it was time to stop tapping into an unknown wire. So I set up a 40A SPDT and used that unknown wire as my trigger. Well here is the problem, ever since I did this set up my battery dies after 8-10 hours. The relay seems to be working properly. When the key shuts off everything attached to the relay does too. What am I missing? Why is my battery now draining?

Your relay coil, 86 and 87. Is one a 12V+constant? Also have you dioded across the coil?

No diode, wiring as followed 30-12v constant 85-12v Trigger 86-Ground 87-to distribution block 87a-empty

Is the trigger wire at 85 ignition switched or constant? Also turn around 85 and 86, there's a reason. 86 is the convention for coil plus, some relays have built in diodes, marked on the casing, that may be the reason. You should then install a diode, 1N4004 across the 85 and 86 terminals, band to 86.

You don't just tap off random wires under the dash or anywhere. You have probably tapped a constant 12V wire. You at least test first for voltage, and then see if using it damages anything - whether fuses, ECUs, O2 sensors etc. Aftermarket gauges can probably be added to the existing gauge circuit.

I should have been a little more clear on the "random wire" it is a switched 12v source and is most likely the factory clusters 12v source. It IS NOT anything critical, it runs through the main internal disconnect. AKA not engine/performance related. Okay I will swap the two leads and install a diode if not already inside the relay.

LOL - when some people say "random", they mean just that. I'll assume too you picked an on during cranking (and IGN) as opposed to an ACC +12V that is off during cranking. Not that that is critical, but dash gauges are usually kept on during cranking (and or NOT on in ACC). If your relay did have an internal (spike protection) diode, then your inverted #85 & #86 connection should have blown the diode else its fuse. It's unlikely to have have survived to drain the battery unless the wires used for #85 or #86 were small and of high resistance (ie, big enough to not fuse, but small enough to limit to a 1A current). Though that is unlikely, it is a freak (or well designed) possibility.

Haha I believe it "I tapped the black wire and it won't turn on!" Lol. Well I hear the relay click on an off? That's what is so weird...I will swap the wires and replace the relay, I have 10 of them lol.

Assuming that by black wire you meant as a (constant!) GND for the relay coil... Alas not all black wires are GND though most are (or should be!!) but even when GND, it may not mean constant GND. I recall door ground switches for dome lights etc, but more modern vehicles probably have a trace color to differentiate from a GND or even to show which circuit it belongs to. My vehicle uses a B/W wire (black with white trace) for its +12V IGN switch Start (else its intermediate relay) to the starter-motor's solenoid, and that's common with many Jap cars (mine being an old Isuzu). It's a heavy wire needing to carry ~20A (or 40A if the battery +12V heavy to starter is not connected) and one that should not be confused with GND wiring, though unfortunately it does test like a solid GND when not cranking. Whilst the above may be a useful warning for some, I suspect you'll see its frivolity. But I must admit my main ramble reason - a distraction before I start an on-line test (cognitive skills). Man o man, I always excelled at those, but I realised during the 5-test sample quiz how long it's been (like well over a decade). And I felt the pressure too! I NEVER feel pressure. Even my last permanent employment which ended in 2005, the only pressure I felt was self induced else when it came to deciding between legals or what is ethical or right when it conflicted with directives. Even that was no pressure wrt to my decision, but merely wrt how far I would take it... ... and the likely repercussions, not that the reapers I've known use cussions). I have had that problem in several jobs since then, but I've considered those more of an enjoyment. (Yeah, wrong-doing or ignorant employers tend not to like me... ) Oh well, I've showered and had my coffee - that's a rarity before my forum replies (some would suggest "obviously"... LOL). I'd better continue my doom.

Never ASSUME from a colour. French and Germans (GM) use black as a constant feed. BLACK/ white an ignition or starter feed on some Japanese. Black = ignition on some Germans. Black = Ground on (older British and US). Brown = Battery feed on older British, main straight to ground on German. There are NO colour codes on French cars, they use tiny numbers embossed on the wiring. Do you see where this is going? TEST.