voltage loss data

[psyguy]

found a seemingly nice relay with a fuse incorporated as well as the mounting bracket, is this a good idea?

[Matchless]

It seems as if that fuse is on the input side of the contact i.e. #30 that means you are fusing/protecting the wire feeding the power form the relay to the coils. If you mount the relay any where further than the sidepanel I would suggest that you still use a fuse for the main supply as close to the battery as possible. The reason is protection, any wire shorted should blow a fuse rather than overheating and starting a fire. So that relay is excellent, but you may still need an additional fuse for the new positive supply from the battery.

[psyguy]

ok, so i've read this and other related threads enough times to feel confident i can do this mod [-o<
checking the voltage loss, from 12.4v at the battery the coils get 11.4v and the headlight 11.2v

now, does this level of voltage drop warants the instalation of relays?

[Kcwiro]

Go for it

ok, so i've read this and other related threads enough times to feel confident i can do this mod [-o<
checking the voltage loss, from 12.4v at the battery the coils get 11.4v and the headlight 11.2v

now, does this level of voltage drop warants the instalation of relays?

do you even have to ask?... I would do it just becuase it is more quality time with the GS ...not really hard to do. Cept I am still waiting on the headlight mod...just have relay done for now.

[psyguy]

do you even have to ask?... I would do it just becuase it is more quality time with the GS ...not really hard to do. Cept I am still waiting on the headlight mod...just have relay done for now.

yea, i know that, thanks, by asking the question i kind of wanted to learn more about the elctrics (lol)

[Matchless]

Again Hi psyguy,
As you said you want to know more about the electrics, hope this gives you a better insight into the issue.
That voltage drop will become even more significant as more current is drawn on that feed. With headlights on and brake light on, check the voltage at the battery again and at the the coils and headlight. Also try and blow the horn at the same time, it may have trouble. Do your flashers flash at the same speed when headlight and brake light is on?
A small part of the drop is a design factor and will be over the total length of the wire and allowed the designers to use the minimal diameter copper that would do the job. Thereafter age and other gremlins, like owner doing some funny things to the electrical system, starts taking their toll and if you are the persistant type you may be able to localise each drop and maybe even clean a contact to give minimal or no voltage drop, but then you land up with your 28 year old wiring and they may have a more significant drop and you again can clean them, but may find them worn and hard to get as new.
The relay mod does two things, it provides a completely new and heavier supply wire with brand new connectors for only that circuit, such as the coils or headlight, with its own fuse (new type) and removes the heavy current from the old thinner supply wire. It also routes the wire carrying the load via a relay with brand new contacts that are gold, paladium or platinum plated and uses a direct path instead of going via numerous other connections, such as the original stock wire did. A relay coil is not so sensitive to a slight voltage variation and also requires very little current to operate.
In theory the negative or earth wire should be used at all terminating points, but should be earthed to the frame at that point as well and then taken further, but one sometimes sees a negative wire that is only earthed at the start of its run. This puts the return path of all the battery operated items on the full length of the negative wire, where the frame could have helped to beef up the ground conduction path. In other cases one sees a negative picked up from the frame, but the earth wire to frame is a long way off and that connection is corroded and could even be hot to the touch.
This all just means that any electrical path needs a good positive and negative feed to make it work properly and manufacturers seldom run extra wires or thicker wires or add extra relays, the cost, the bulk and space can affect profits and they hoped you will buy a new bike every few years and not refurbish you old one 28 years down the line!
Very similar issues can be found on older motor vehicles and if you search on Google you will find many such modifications as these were an older technology, many manufacturers copied each other and kept it simple in those days. Once computers and electronic fuel injection started taking hold all vehicles have undergone radical changes to the wiring and fitting of components. For example the connectors used in many motor vehicles today are a major improvement.
Hope this helps a bit.

[Matchless]

Yes, this is the practical approach for a bike with old wiring, use the frame, but additionally run a direct earth with clean and good terminating surfaces. The "thiness" of earth wire will be determined by the current drawn on the positive side and then the same current via the earth wire. Ideally the same thickness.

Look at a starter in a car. The first heavy red wire goes directly to the starter/solenoid, heavy enough to carry all the amps that the starter requires. The first earth strap or negative wire to the frame is just as heavy as the positive and is terminated as close to the starter as possible. When the starter is turning the current to the starter motor runs through both wires. If you put a thin earth wire there you may find it heating up and maybe even burning out.You will then also find lighter earth straps to jump over a mounting and to the chassis and body. If one of these go bad, everything that picks its earth up from say the body will not be earthed properly.
The first fix for the GS's most people have done is the earth strap on the battery to the regulator. So instead of depending on the chassis or frame to conduct the earth you actually double up on this with a nice heavy wire. The practical approach would be the same for other earths on the bike, especially when you land up in the headlamp shroud, any metal around there is connected to the main frame via a couple of bearings on grease and maybe a metal outer of a cable. I personally would want a proper earth conductor to connect to there, that goes back to the battery, then it could be bonded to the steering frame AND the main frame, but again metal that is clamped and was clamped together 28 years ago may not be making a good electrical contact any more, so a direct wire again is the safest bet.

When drawing high current at 12 volts a measurable voltage drop develops over thinner copper and longer and less so over thicker and shorter. The rule is the longer the wire the thicker the copper, the higher the current (amps) drawn the thicker the copper. Use only very thin automotive wire for light current items such a gauges, dash lights, relays etc. If in doubt go heavier. Also keep in mind the accumalative effect when you have a single earth wire of a specific gauge and more than one (i.e. 3) positive wires of the same gauge using the single earth as a common conductor, if all three positives are drawing maximum current the poor earth wire will be handling 3 times as much as each positive wire on its own. Here the earthing to chassis and frame becomes important to helps conduct the much heavier load.
Hope this helps you "see" it in your minds eye.

[82Shafty]

I believe this to be the relay junkies thread!

I'm going to have to go home and bust out the DVOM now.

[82Shafty]

I found a 1.5V drop at my coils and well, I went and got the chinee 4 pronger from Autozone to hook it up for the mean time.

I also set it up for if any reason the aftermarket relay fails, I can plug in the stock wires to get me home.

Perhaps in due time, I will upgrade to one of the TYCO relays.

[peterpressure]

Any updates from anyone on this topic? I was thinking of performing this mod over the weekend, but I have a Motorcycle Safety Test on Monday and don't want to mess up my bike!

[peterpressure]

Finished!

Voltage before:
12.5 at battery
11.25 at coils

Voltage after:
12.5 at battery
12.4 at coils

Another happy customer!!

Took me a few hours, first time working on the electrical stuff on this bike. PO covered everything with electrical tape.

I left all the original wiring completely together and just took the 2 old Coil POWER "eye" butts and added another "eye" butt for the "trigger" plug on the relay. Bolted all 3 together, so if I ever need to I can just disconnect it all and go back to stock wiring.

Bike cut out once for a second on the highway, but probably because it was running better and faster then I have had her before! Definitely more power in the high end. I'll check my "trigger" connection again and Main ground again.

[peterpressure]

Update:
Recently my engine cut out a few times on the highway so I went back to my stock wiring. When I first performed the mod I left all the stock wiring in place and simly ran a wire connecting to both of the old Positive connections to the coils.

Also I tested again recently and I was again losing like .5 at my coils even with the relay mod. I must have a bad connection somewhere. I will try and rewire the relay again this weekend...