First post! And I need help with my horn...

[G50911]

Hello all!

As the title states this is my first post and I need some help. I have a 68 with the old style horn. I wanted to update it to the trumpet style and for some reason the new horns don't work. Here's what I know:

1) Old horn works but swapping to new ones don't
2) I hear the new ones need a better ground?
3) I also hear an updated relay would work

Can anyone help identify the contacts on my old relay? I've labeled them on this image:


My old relay is old and I cant read the contacts so which one is 87, 87A, 85, 86, 30?:
A = ?
B = ?
C = ?
D = ?
E = ?

[Jim Breazeale]

If you have power to the old horns and they work, there is no reason why the new ones wouldn't work just as well or better.

Ciao

Jim

[G50911]

Thanks for the reply Jim. I'm not sure I agree with you. Is there anyone that can verify my questions #2 and #3 above or what Jim's saying?

[304065]

Everything about SWB relays is here: http://www.early911sregistry.org/for...elays-Analyzed

A = 87 (pair of fat reds, one is power wire, other is a multiple to 86 (relay coil POSITIVE)
B = 30/51 (black/yellow)
C = 86 red multiple from 87 (relay coil POSITIVE)
D = 30/51 (black/yellow) order doesn't matter at this is a cross connect between the two black/yellows
E = 85 (switched ground (brown with white tracer) relay coil NEGATIVE)

So yours is mostly correct, except you have the relay coil positive and negative reversed (not critical in a relay without a quench diode but not right either) and you have the fat red on the relay positive with the multiple to 87 instead of on 87 with the multiple to the relay positive. Again, electrically OK but harder to troubleshoot (especially over the internet).

Nothing wrong I guess with the Bosch ice cube relays (not made by Bosch anymore) but as you can see yours doesn't have a place for the second 30/51 wire, so you need one of those male fastons with a female/male end on it (maybe try Digikey) or a power relay with a dual 87. (If you do get a dual 87 then you need to put the 30/51 black/yellow on each 87 terminal and then put the fat red on 30 (with multiple to 86).



http://www.rallylights.com/all/elect...d-bracket.html

[304065]

What Jim means is that if your existing relay is adequate to power the old-style UFO or snail-shell horns, it's adequate to power the later trumpet-style. There is nothing about a modern horn that is electrically different from an early one. They both draw a certain amount of amps which your relay should be able to handle. If it doesn't handle it, the defect is in the relay-- if you carefully pry back the metal tabs that hold the phenolic base to the can, you can pull off the can (it's not sealed to weather) and can see the coil and contacts inside (probably rusty).

That said, SAVE everything-- almost without exception in the Porsche world, no matter how good a replacement seems to be, it's not made like the original.

[G50911]

it works!!!

i plugged in a new relay and connected my + lead from the new horn to B/D and then connected the - to a good ground spot on the chassis. it scared the crap out of me when it worked but it works none the less.

thanks guys! looking forward to learning more from this forum.