Relay upgrades for '79 GS850G

[sarathchandars]

I agree.. I'm not adding another circuit for the starter. But planning to add relays for the headlight and horns. I was figuring out the rating for the starter relay to replace the existing one because it is clearly old and the terminals are rusting.

 

[pdqford]

But planning to add relays for the headlight and horns.

The whole electrical system is fused at 15 amps.

The full lighting system is fused at 10 amps.
The "signal" circuit (horns, turn signals) are fused at 10 amps.

That should give you an idea of relay capacity required. for the original system.

Put your meter across your big new horns and measure the resistance.
Divide 15 by that resistance and the result will be the amps draw of those new horns.
Be sure the wire gauge can handle that amount of current for best results.

 

[sarathchandars]

Thanks Jim, this is super helpful...

 

[Griffin]

The bike already has a starter relay. Don't add another into that circuit. Some people add a relay to feed voltage to the coils. That's, arguably, the only relay that will be beneficial.

I did that to a couple of my GSes about 18 years ago. That was one of the "things to do to a new-to-you GS" back in the day. Gained between 1 - 1.5 volts at the coils. These bikes are cold starting, one crank and fire up wonders.

I was reminded of it today when I did a brain fart and installed a new battery backwards, frying the main fuse. I checked the other fuses, they were fine. I changed the main and hit the starter button after she was all buttoned up. Nothing. No click, nothing.

Oh yeah, there's a 10 amp fuse in my coil relay mod. Checked it, it was fried. Replaced that fuse and all is well again.

Something to think about if you buy a GS from a GSR old timer like me. There might be an extra fuse lurking somewhere under the gas tank.

The relay is circled in black. The fuse holder in blue.

 

[salty_monk]

I did mine through one of these fuse boxes and put a relay in front of it. https://www.easternbeaver.com/Main/Wiring_Kits/Fuseboxes/PC-8/pc-8.html These ones are also well thought of if you want an integrated relay: https://www.fuzeblocks.com/

There are also some clever "programmable" ones on the market now..... Rowe, Motogadget etc.