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problem with horn relay

  • Thread starter Thread starter p_s
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p_s

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The main ignition switch on my '85 GS550ES was dropping some voltage, so I added a 30 amp horn relay. It worked great in my garage, and then after 3 blocks the main fuse burnt up and when I got home the relay was dead as well. (No continuity between the switching terminals--86 and 85. No more click. Dead.)

I wired it with frame ground to 85, orange wire from ignition switch to 86, and then 12v+ through 87 and 30 to the fuse box.

In other words, the trigger side from the ignition switch was going through the main fuse, and then the 12v+ when the relay was active was passing through a fuse I wired in and then all the other fuses in the fusebox.

Are these relays not specced for constant use? Bad installation (all the wires had plastic insulators everywhere)? Just bad luck?
 
Not sure you had it connected correctly. You don't want any of the terminals connected directly to ground. Easiest way is to take the two original horn wires and connect them to 85 and 86 on the relay. (One of them will be hot whenever the key is on, the other will be grounded when you push the horn button.) Connect terminal 30 to power (through a fuse) and connect 87 to the horn(s). The other terminal on the horns should be connected to ground.

These relays are spec'ed for constant use. I use several on most of my vehicles for fog lights, trailer marker lights and other goodies. Out of 20+ relays spread out over 5 or 6 vehicles, I might have to change 1 a year, which is not too bad.

.
 
Steve said:
Not sure you had it connected correctly. You don't want any of the terminals connected directly to ground.
Click to expand...
Sorry, the subject line is misleading. I'm using a generic horn relay from NAPA to make up for the voltage drop on my ignition switch. The horn has nothing to do with it.
 
andrewclaycomb said:
So this is for the coil relay mod?
Click to expand...
Kind of. Actually my starter relay was not getting enough voltage to fire. I found most of the drop was only in the main ignition switch, so I just put the relay around it. I found not much of a drop at all anywhere else.

The only thing I can think of is that the coil inside the relay somehow shorted out and burned up the main fuse. I guess I'll buy another and see what happens. :shock:
 
what size fuse did you put inline with the relay? That should have blown well before the relay would.
 
andrewclaycomb said:
what size fuse did you put inline with the relay? That should have blown well before the relay would.
Click to expand...
Well inline with the 12v+ from the battery to the relay I put 15 amps, which is spec--and it didn't blow.

The fuse that blew was the main fuse in the fuse box that was in the circuit with the trigger side of the relay. There's no continuity across the coil in the relay anymore.
 
A horn relay is meant for intermittent use. So is a starter relay or solenoid.

If you want constant use, use a fog light relay.

.
 
Steve said:
A horn relay is meant for intermittent use. So is a starter relay or solenoid.

If you want constant use, use a fog light relay.
Click to expand...
Ah, that explains it. Somehow I got it in my head that a horn relay was okay for everything.
 
In the coil relay mod a lot of people are using horn relay without any problems. It seems like it should have taken it. I'm wondering why the main fuse blew and why that messed up the horn relay but left the in line fuse alone.
 
andrewclaycomb said:
In the coil relay mod a lot of people are using horn relay without any problems. It seems like it should have taken it. I'm wondering why the main fuse blew and why that messed up the horn relay but left the in line fuse alone.
Click to expand...
The in-line fuse is on the switched 12v+ from the battery. So it wasn't involved. The only thing that makes sense to me is that the coil in the relay shorted out internally, which would send massive current through the main fuse, which is the only thing between the relay coil and the battery (besides the main ignition switch). Then ... somehow the coil became an open circuit.

It worked for a few blocks with a new horn relay, but I'm going to get a fog light relay tomorrow and go for a ride and see what happens.
 
Steve said:
A horn relay is meant for intermittent use. So is a starter relay or solenoid.

If you want constant use, use a fog light relay.
Click to expand...
I took the horn relay back to NAPA to exchange for a fog light relay, and the cashier asked me some very confused questions and it turns out what I had was an accessory relay suitable for fog lights or any constant use device. *shrug*
 
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