Author Topic: Horn Relay as Starter Relay?  (Read 1866 times)

Offline Scoozi My Guzzi

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Horn Relay as Starter Relay?
« on: May 13, 2009, 12:31:09 PM »
Can a garden variety analog 12V horn relay be used as a starter relay on an 850T? PO rewired the starter switch without a relay and it also can spin the starter without the key. This also puts all the current through the switch. I happen to have a NOS 80s vintage horn relay in stock.
1974 850T Black Cafe

Offline rodekyll

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Re: Horn Relay as Starter Relay?
« Reply #1 on: May 13, 2009, 12:37:53 PM »
If the relay has a sufficient amperage rating, yes.

Wayne Orwig

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Re: Horn Relay as Starter Relay?
« Reply #2 on: May 13, 2009, 12:47:30 PM »
Some horn relays are intended for intermittent use. They may overheat if left on for something like driving lights. But they should be fine for a starter.

Offline Goose

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Re: Horn Relay as Starter Relay?
« Reply #3 on: May 13, 2009, 01:42:00 PM »
Some horn relays are intended for intermittent use. They may overheat if left on for something like driving lights. But they should be fine for a starter.


Being that I will be installing lights this weekend...I was going to use a 30amp relay from Radio shack. Are they long or short duration?

Wayne Orwig

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Re: Horn Relay as Starter Relay?
« Reply #4 on: May 13, 2009, 02:20:15 PM »
Some horn relays are intended for intermittent use. They may overheat if left on for something like driving lights. But they should be fine for a starter.

from Radio shack. Are they long or short duration?

Radio Shack has been around for years.











 ::)

You'll need to look at the spec. Most are continuous duty unless they say otherwise.

Offline WeirdTim

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Re: Horn Relay as Starter Relay?
« Reply #5 on: May 13, 2009, 02:24:53 PM »
I usually just buy a relay intended for fog lamps.  The numbers next to the pins on the stock 850T relay will be the same on a standard four or five pin fog light relay.  The nice part is you can buy a socket for the four/five pin relays and relocate it underneath the seat near the fuse box. 
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Offline Pfaff!

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Re: Horn Relay as Starter Relay?
« Reply #6 on: May 13, 2009, 03:07:52 PM »
Scusi my ignorance,

-but wouldn't the "starter relay" questioned just be pulling the solenoid, the relay which really is taking the load?
In that case any relay probably would be usable, as the current for the solenoid coil is very low.
Anders Holt

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Wayne Orwig

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Re: Horn Relay as Starter Relay?
« Reply #7 on: May 13, 2009, 03:21:57 PM »
Scusi my ignorance,

-but wouldn't the "starter relay" questioned just be pulling the solenoid, the relay which really is taking the load?
In that case any relay probably would be usable, as the current for the solenoid coil is very low.

Sort of. But a solenoid actually takes a lot of current. Easily 10 amps or so.
But even worse, when it releases the coil there is a huge back EMF spike and arc. The contacts on a whimpy relay would get burned quickly by that.

Offline tocino

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Re: Horn Relay as Starter Relay?
« Reply #8 on: May 15, 2009, 01:34:22 PM »
I wanted to hook up some relays for the headlight (high & low) and the horn. Where does one get these? Radio Shack? Generic auto-parts store? I know if I walk into either of these (the ones in my area anyways) and ask for a relay I'll probably get a blank stare - or worse: get asked what kind? :)

Do I just ask for a generic automotive relay of ?? amps? Specific Radio Shack part #?

I can do wiring and all that, but I have no idea how to identify the type of relay I would need, nor how to ask the counter guy for the appropriate ones.

And am I correct in understanding that (at least for my 850-T) there is NOT a relay between the starter switch to the starter solenoid? So that'd be *4* relays I should add?

thanks all
  Steve

Offline Dharma Bum

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Re: Horn Relay as Starter Relay?
« Reply #9 on: May 15, 2009, 01:45:01 PM »
I have used NAPA relays for replacements on my '96 Cali.  Part # AR606 are 5 pin relays that plug right into the stock receptacles.

Offline rjamesohio

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Re: Horn Relay as Starter Relay?
« Reply #10 on: May 15, 2009, 02:33:14 PM »
I recently installed a 30 AMP 'generic' relay on a BMW that used a Bosch Starter, it works beautifully. And - you can get them at any auto parts store, so interchangeability is great.

Photo of installation on a BMW is below - note relay to the left, and harness leading up to it would allow plug-in replacment of the relay if it ever failed. Harnesses are available from most good automotive shop as well.

Replacement cost with the old-style Bosch relay? $75. I install these for my customers for 1/3 of that.

The ones I use typically have the following terminals:

87
87a
85
86
30



Our friend Dave Richardson and his excellent reference Guzziology will show you how to wire them up, but if you need help I can make some suggestions off-line
Ron James
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LURP01

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Re: Horn Relay as Starter Relay?
« Reply #11 on: May 15, 2009, 03:39:24 PM »
Go to a auto salvage yard {junk yard} Find an 80s model Volvo. Look on the left inner fender and about any amp relay you need will be there. If those are gone look under the dash, there be a few more there. They have the amp load marked on them. 
  I just cut the wires and keep the connectors also, Make a real neat installation.
I forget what wire number does what but I can get you the info if you go this route. They are small and easy to stow.

Offline rodekyll

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Re: Horn Relay as Starter Relay?
« Reply #12 on: May 15, 2009, 04:15:55 PM »
Go to a auto salvage yard {junk yard} Find an 80s model Volvo. Look on the left inner fender and about any amp relay you need will be there. If those are gone look under the dash, there be a few more there. They have the amp load marked on them. 
  I just cut the wires and keep the connectors also, Make a real neat installation.
I forget what wire number does what but I can get you the info if you go this route. They are small and easy to stow.

+1

I strip fuses, relays, light bulbs, wiring harnesses, and fasteners from junked cars for the stash.  My junkyard shopping saves my a$$ regularly.

Offline rjamesohio

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Re: Horn Relay as Starter Relay?
« Reply #13 on: May 15, 2009, 04:23:37 PM »
Good info on the Volvo  relays.

That said - the generic relays are not that expensive, and you have a NEW non-corroded version. My money is on a new electrical part every time, as the amount saved on using used, unknown electrical parts is generally not worth it, especially for the price of a relay!

Starters, generators, et al are different, as they can be inspected, brushes re-newed.

Just my opinion, but if you're stranded and a Volvo junk yard is handy, it's always good to know that.

Rocket
« Last Edit: May 16, 2009, 12:16:07 PM by rjamesohio »
Ron James
Appalachian Spring Rally
http://wildguzzi.com/forum/index.php?topic=59640.40
Ex LM V - somewhere in NE Ohio
Ex SP1000 - now in Australia with Morizzi
Ex Eldorado - living in KY now
Ex Quota - parts live on
Waynesville, Ohio
937-886-2665

LURP01

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Re: Horn Relay as Starter Relay?
« Reply #14 on: May 15, 2009, 05:07:34 PM »
Naw, ya cain't trust old Volvo relays.                                                                                                                             
I melted the starter switch,  I used to work on old Volvos when my  work was slack in the early 80s and
had a few relays laying around so I installed one into the system. It is still there. Since them I have seperated the high & low beams,turn signals L&R and have breakers{from  behind the  light cord receptical from a semi trailer.}
  When I bought the bike new I had the dealer put on a Califia fairing, with an amp and oil gauge mouted in the fairing dash. Well while they were mounting the fairing they crushed the wire to the side stand under a 'U ' bolt and burn't most of the wiring up. I was told that
 they had to replace the entire harness, butttttt- ?? thats where my electical problems started.
It worked fine for a few years until the butt connectors started eroding, they had slipped them into what looked like shrink wrap tubing so as not to show cutting into the original harness, only not shrunk. This is where I found my problems.
    BTW the mechanic ended up later being my son -in - law. He offered to help me sort thing out and I turned him down.I flat told him that I wouldn't let him work on my lawn mower, let alone the Guzzi.
    He ain't my son in law any more, but he does have a job fixing lawn mowers now ;D
   
« Last Edit: May 15, 2009, 06:46:38 PM by LURP01 »

Offline LarryinKC

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Re: Horn Relay as Starter Relay?
« Reply #15 on: May 16, 2009, 09:37:58 AM »
I used a single pole double throw relay as a starter relay and run the head and tail light through the side of the relay that is normally closed.

When the starter button energizes the relay to start the motor the lights are turned off while the starter is cranking the engine.

Offline tocino

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Re: Horn Relay as Starter Relay?
« Reply #16 on: May 16, 2009, 01:35:19 PM »
Thanks -

so what amp relays for:
horn
high / low beams
starter
?
Or do I just use 40 amp relays for them all?


Offline rodekyll

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Re: Horn Relay as Starter Relay?
« Reply #17 on: May 16, 2009, 02:31:05 PM »
40 should be good.  Overkill, but good.

 

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