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One call a/c
01-20-2014, 02:57 AM
Hello. Looking to power the horn circuit constant so I can use it for my alarm system. I know the relay is neg triggered and I tried to power the relay with a constant positive with no luck. Any thoughts ? :idunno:
2006 dodge sprinter

ECU
01-20-2014, 03:21 AM
How about adding a relay that grounds when active and add it in that way.

One call a/c
01-20-2014, 03:39 AM
My problem is the relay is fed from a 15 amp fuse that powers other vital circuits. I need the horn circuit to be hot all the time if possible. I tried to feed 12v to the relay but there's something else in the way ?

ECU
01-20-2014, 04:24 AM
The power to the horn is only on with the ignition key. So you need to feed power to the hot side as well as grounding. Does your alarm have enough current to feed the horn directly?
In the picture you can see that the green wire is 12v that feeds the horn at #85.
At the same time the alarm trigger will trip a relay you add in to give the relay a ground. This will trip the horn relay and connect the horn to ground. OR you could connect the grounding relay NO (normally open) to #87 on the horn relay and this will trigger the horn without triggering the horn relay.
Not that I've done this, just looking at the diagrams.
57008
After looking at this, it might fire up the entire circuit. All the other stuff. You might have to put a double pole relay in to the horn. If that is the case, you might just be as well off to add a new horn/siren to the mix.

One call a/c
01-20-2014, 03:11 PM
I did try to cut and feed power to 85. The relay triggers with the push of the horn button but no horn.

One call a/c
01-20-2014, 03:12 PM
When I tried to power 85 while still connected it powers up all kinds if other stuff.

Aqua Puttana
01-20-2014, 03:23 PM
When I tried to power 85 while still connected it powers up all kinds if other stuff.
A polarity blocking diode installed in the correct position of the circuit should stop the backfeed. S206 is a splice point.

I don't know the horn draw. A 3 amp diode is probably enough, 5 amp rating would be better. Radio Shack sells them. vic

57010

autostaretx
01-20-2014, 07:15 PM
sigh... How To Read A Sprinter Wiring Diagram (and the steps you've gotta take...) :professor:

Vic posted: (trimmed to area of interest):
57019

See the (circled) 8w-10-22? That means you *really want* to go look at THAT page.

57020

... which shows every thing *else* that attaches to that "splice" (S206)

The actual physical "splicing" may not happen at only one point along the wire.

--dick
p.s. personal opinion: the OEM Sprinter "horn" is so pitifully weak.. (could you hear it in a crowed theater, even if it was sitting only two rows back?)(is someone stealing an old VW bug?).. why not install a separate noisemaker in a place that's not so easy to reach (and unplug)? (MB does when they're installing the factory alarm)

p.p.s. this was NOT meant to be a "dump on Vic" :hugs: (he knows this stuff)... it's to help future readers who might not

Aqua Puttana
01-20-2014, 07:49 PM
sigh... ...

Hence my comment.
A polarity blocking diode installed in the correct position of the circuit should stop the backfeed.
I suppose I was a bit short.
S206 is a splice point edit: which you should investigate enough to determine where in the circuit the polarity blocking diode should be installed.
...
I often provide suggestions, not detailed design. Messing with things without a bit of background can be dangerous. I know that from personal experience. :bash: Sorry for any confusion.


p.s. personal opinion: the OEM Sprinter "horn" is so pitifully weak.. (could you hear it in a crowed theater, even if it was sitting only two rows back?)(is someone stealing an old VW bug?).. why not install a separate noisemaker in a place that's not so easy to reach (and unplug)? (MB does when they're installing the factory alarm)
I agree. I will add that based upon my next door neighbor's string of false alarms I would be happier if they had used a Sprinter horn.

vic

autostaretx
01-20-2014, 08:37 PM
I wrote: "The actual physical "splicing" may not happen at only one point along the wire."

Looking at the schematic diagram, i would have expected the splice to be "distributed" through the Sprinter.
Nope.
Since the power arises on Fuse Block 1 (under the steering wheel), good old S206 may be in the worst possible place for "tapping in" to one leg...
It's in the nexus where it passes through the firewall.

57021
(page 8w-91-31 in the 2006 manual)

--dick

Aqua Puttana
01-20-2014, 10:16 PM
sigh...

p.p.s. this was NOT meant to be a "dump on Vic" :hugs: (sometimes he knows this stuff)... it's to help future readers who might not
Thanks. I fixed it for you.

To continue on your course.

There is some pretty good description and overview included in the first pages of the 8W Section of the Service Manual. These pages should be enough to give the idea. There are even more pages in the manual.

57025

57026

57027

57028

57029

vic

hulagun
01-20-2014, 11:15 PM
I'm gonna agree with the recommendation on just adding a separate horn and power feed for the alarm. Far easier than trying to splice into the OEM horn circuit. And any decent horn draws a fair amount of power. The stock horn circuit shows 16 g but in reality it measures out more like 18 or 20g which could burn up under constant use by larger horns.

You can pull constant 12v hot right off the fuse panel at the battery. If you don't have dual A/C compressors there's an unused terminal there, ideal for adding a fused line to power whatever you want under the hood or along the radiator support.

I did this when I replaced the stock beeper with dual Fiamm horns. Not wanting to feed two horns thru the OEM relay I added a second one near the horns, and triggered it using the factory original horn circuit. I wanted the horns to only work with the key on (and when I push on the steering wheel).

I located the inline fuse very near to battery 12v+ source, so that would protect the longest possible run of the new wiring.

One call a/c
01-21-2014, 12:14 AM
I went ahead and cut the positive feed to the horn. Then ran a fused feed from fuse block to horn. Then I cut the feed 85 to relay and feed that with a constant fused and now the horn works even when ignition is off. I may change the stock horn in the near further but at least if I needed attention I can blow the horn without having the key on. I've yet to see a vehicle that you had to have the key on to blow the horn. :/

One call a/c
01-21-2014, 01:09 AM
Thank you all that replied. Greatly appreciated. And the info from the service manual is awesome. !!

Aqua Puttana
01-21-2014, 01:43 AM
... I've yet to see a vehicle that you had to have the key on to blow the horn. :/
From my memory that is pretty much standard on the VW, Porsche, Mercedes, etc. German made vehicles with the '60's models when I started working on them.

You are probably more familiar with Detroit iron.

vic

autostaretx
01-22-2014, 04:35 AM
Thank you all that replied. Greatly appreciated. And the info from the service manual is awesome. !!

If you haven't grabbed it yet, the full 2006 service manual set can be downloaded from:
http://aie-services-2.net/Sprinter/

--dick