led backup lights and remote start

This reminds me of (I think it was) a cruise control that had a similar issue where it needed a pull-down (resistance) to GND to work. However the solution the manufacturer's site gave was totally wrong and (naturally) blew fuses. It's not one of the brands above, and yes - it was written about on the12volt. And yes, it is still in the back of my mind to chase up the manufacturers and their stupid solution (and possibly, poor design).     But why brake or reverse LEDs should have a voltage across them? Maybe if some "blown bulb" checking circuit was used, but that would alert after the LEDs were fitted. Oh - stupid me! It's the remote start unit itself. It needs to sense GND - or rather, "not 12V" at the bulbs/LEDs. Hence it has an internal pull up resistor etc (say 1k - 10k) and the LED fwd voltage drop means it never sees GND. Same problem as the cruise control(?) I mentioned... There are hence 2 solutions - either the relay(s), or a resistor to ground which is small enough to pull the remote-start's sensing terminal down enough (maybe 1k?) noting that that resistor has to handle the full 12V. (EG - for a 1/2W resistor and 15V, Rmin = 470 Ohm.) [ Though a diode could be fitted so that the brake +12V doesn't back feed into the added resistor, but that brings in the issue of the design intent of that circuit - ie, blown bulbs/LEDs or no connection to the lights renders the remote start or cruise control etc inoperative. But then these circuits should be triggered from the brake & reverse etc switches - not their lights. ] BTW Howard - can't you combine those 2 relays into 1 by ORing (diode isolating) the 2 inputs?

Yes of course you can but I was designing that circuit as I was drawing it. I have so many relays, I should have thought of it. Keep the two inputs, diode separate the inputs, 2 amps on each so you'd need 1N5404s and either the blue/white or the blue/green either would be the only one needed.

Here you go:- 8D3_brake_and_reverse,_relay_isolation.bmp

I'm a complete fool, this should be far simpler with apologies to all and thanks to Oldspark for the wake-up call. All you need are a pair of 1N5402/3/4 diodes. Radio Shack etc. D39_brake_and_reverse,_relay_isolation.bmp It should now be called brake and reverse, DIODE isolation. Doh

Now I'm confused... I was thinking Howard's original diagram only needed 1N400x (1A) diodes since the switches merely turned on the relays (250mA max). [It showed the 2 switches each thru diodes to a single relay coil #86, but Howard has now substituted that with the new diagram - and I failed to save the original as evidence!] Not that I'm here about that - nor will I try to clear my head enough to reassess the new diagram... But FYI - I finally found that old thread. [After searching my old posts - trying to remember "when" and what the thread could be called, and then reading thru a few (hence my unclear head!) - I finally googled. Gotta love google's site:the12volt.com and using "oldpsark" to avoid returns for old spark...] It's the 5-pager led third brake light relay started by bbstacker 7072 and involving the usual suspects howie ll and myself with racerjames76 popping in later for a 3-way interchange before bbstacker returns on page 5. I still intend to follow up on this Rostra issue - especially now that I have recovered that thread - but I'll see what updates they have made since, not that their rostra.com/rostra-support page has changed. (Note my mistake in my first reply to bbstacker's thread. I state that Rostra say "do not let the violet wire see ground...". In fact the full line is "LEDs do not let the violet wire see ground...". Does that show the dangers of my improper reading, or the dangers with poor paragraph/sentence formatting? I'll blame Rostra since they also ground #86 of the relay instead of #85...) And I'll have to review what the problem was. As I recall, it was a short from the +12V brake switch else +12V to GND in some implementations, but maybe it's been where LED users use diode type spike protected relays? (I was going to add "how embarrassing", but I'm not. However it supports my oft written & stated view that ANYONE can be wrong or make mistakes. At least I'm still right about that!) Now with big apologies to flip_5 for this hijack (albeit related by subject issue) though that other thread mentions the same resistor solution or its equivalent but non-elegant standard bulb in parallel. I'll get back to the relay solution later, though I was thinking of merely using 1N400x diodes to a common #86 and relay for the Solaris. (If 2 circuits - namely brake and reverse - then a single relay should still be fine.)   

No Peter on that last diagram I'm was admittedly thinking incandescant bulb but since they are LED bulbs, subject to me not knowing the current draw I stuck with 1N54XX as a safety. 1N4004 are probably adequate.

Peter, I'm usually trying to answer 3 posts at once, chat with 2 or 3 other members via PM and email, sort out and research my next install, all at the same time, plus be nice for a change to the morons plus fighting off senile dementia. Give us a break cobber.

Yeah, we are the same. I know exactly what you mean with multi-threading (PC cores only recently got that to work, and they are far younger than us) - just look at my messes - it was only a few weeks ago I had another bad spate hereon. Me give you a break? No - you give yourself a break. That's why I'm not "thinking" about these latest replies now - I don't want to break myself! LOL... Certainly not intended to crit or hound etc. Besides, me hound or crit you? Sorry man, but even if I did, with all your concise "bang on" knowledgeable replies, what credibility would I have? As to the odd mistake - if indeed they are mistakes - geez, make more. I bewonder how more are NOT made with so many things going on! Please join us mere humans... But now to leave for that other world. Maybe I'll be fresher upon my return (for this thread, and maybe my Rostram speech). (Never too tired for puns?)