Another /6 Electrical Question

[wa1nca]

Yes
The amazon relay is different and has a 87a unlike the BMW relay with a 87b terminal

[RideSolo]

Thank you, Tom,

So, looks like the problem is the difference between the relay w/ 87a and 87b terminals. Gotta find an 87b. OK, so be it, the search begins. As I said before I've found them listed as BMW part$ from $30 to $99 at various places. Let's see what I can find, if anything, for less!

[RideSolo]

Interesting, looks like the 87a is much more common than the 87b. What's the difference between an 87/87 and an 87/87b? It looks to me like the 87/87 powers both terminals as does the 87/87b but differently. Does it matter as long as both are energized?

https://www.amazon.com/HELLA-Main-Curre ... B008R8KFG6

[RideSolo]

Well, I did lotsa research and the 87a is the most common, there are 87/87 relays if you hunt for them, and seemingly the majority of the few 87b units are easier found in Europe. Then I fired off a text to my electrical engineer older brother who I lovingly refer to as The Mad Scientist. But he didn't answer, so...

EME, MaxBMW, and B2V have been my favored BMW part$ suppliers for this project and William and the good folks at B2V had the best price and shipping in this case so here's hoping they'll have it to me before the end of the week!

[Darryl.Richman]

The diagrams on each relay indicate how they work. The 87/87a relays are always powered on one of those two terminals, depending on whether there is power to the 85/86 terminals. 87a is normally hot (NC, or normally closed; when no power to 85/86) and 87 is NO (normally open). The BMW relay 87/87b has both 87 and 87b powered the same way. They are NO, so no power when 85/86 is unpowered.

For a dual horn, you would wire 87 to one horn and 87b to the other horn. If you have a single horn, the wire from 87b is superfluous. The green or green/black wire itself is wired to one of 85 or 86, and the other terminal is wired to the horn button as a ground (a brown wire).

The 87/87a relay is only useful for a single horn*, and even then, 87a would not be used.

*You could use a quick disconnect splitter to take 2 wires off 87 and go to each horn.

[RideSolo]

The diagrams on each relay indicate how they work. The 87/87a relays are always powered on one of those two terminals, depending on whether there is power to the 85/86 terminals. 87a is normally hot (NC, or normally closed; when no power to 85/86) and 87 is NO (normally open). The BMW relay 87/87b has both 87 and 87b powered the same way. They are NO, so no power when 85/86 is unpowered.

For a dual horn, you would wire 87 to one horn and 87b to the other horn. If you have a single horn, the wire from 87b is superfluous. The green or green/black wire itself is wired to one of 85 or 86, and the other terminal is wired to the horn button as a ground (a brown wire).

The 87/87a relay is only useful for a single horn*, and even then, 87a would not be used.

*You could use a quick disconnect splitter to take 2 wires off 87 and go to each horn.

Thank you very much. Yeah, I got a quick education on relays during all my study time last night. I'm pretty sure that though they work slightly differently mechanically but get the same end result, the 87/87b and the 87/87 that Hella has would probably be interchangeable. But since I didn't know that for sure I just ordered the 87b to be done w/ it.

As for a horn, that was an easy no-brainer for me. The existing BMW harness has two wires all set up for a horn so I just picked the best of the two Fiamms I had and plunked it on there. If I were going to travel or commute I might feel more secure w/ something that sounds like a locomotive but the fairly loud Beep Beep that I ended up with will be perfect for my puttering around. However, if I find that I'm needing to get the cages around me to pay better attention I may switch to something louder. For now all is good!

[wa1nca]

Interesting, looks like the 87a is much more common than the 87b. What's the difference between an 87/87 and an 87/87b? It looks to me like the 87/87 powers both terminals as does the 87/87b but differently. Does it matter as long as both are energized?

https://www.amazon.com/HELLA-Main-Curre ... B008R8KFG6

Yes that would have the same function as 30 to 87 + 87b compared to 30 to dual 87,energized on when power to relay coil by 85 & 86
Still 40 amp ratings but not sure if the MINI is physically smaller than the original size and would not fit the socket

Let us know how you make out with the original replacement part

[RideSolo]

Yes that would have the same function as 30 to 87 & 87b compared to 30 to dual 87, energized on when power to relay coil by 85 & 86
Still 40 amp ratings but not sure if the MINI is physically smaller than the original size and would not fit the socket

Let us know how you make out with the original replacement part

Will let you know, for sure. Most likely won't even need to see it here, prolly will just hear me yelling.

In my case the size wouldn't matter because there's no socket, just five wires to plug into the five terminals.

[RideSolo]

Unbelievably... no.

Plugged in the new relay from B2V and the symptoms are the same. Seems like it just about has to be the key switch.

Park lights work front and back; key on park lights, light switch on park light

Park lights work front and back; key on run, light switch on park light

Head light flasher; works as expected, as it should

Headlight, lo and hi, works as expected; key on, light switch to lights, BUT NO TAIL LIGHT

Key OFF, park lights stay on until you disconnect the battery

I've got something else to work on this morning, but I'm going to start going backwards w/ things; i.e., make sure the taillight connections are all connected right, make sure the key switch is connected right (though I've done this already) and carry on. Will even pull the new relay out and make sure it's a 87b and not another 87a... checked that, too.

[wa1nca]

I think i'm getting a headache

Double check the colors going to the new headlight relay
Red to # 30
Yellow to 87
Brown to 85
Grey to 87B
Grey/Green strip to 86

Grey and Grey/green strip wires reversed ?