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voltage leakage to kill wire on new switch

rocknroj

Contributing Member
thanks for your reading

I have merc classic 50 4 banger circa. 1985

just replaced the ignition switch on my new remote control.. used the sierra Mp41070-2. listed as a direct replacement.

I also did a retrofit for a newer rectifier with regulator.. cdi 193-5114 seems like a steady 12.67 voltage reading but need to take my meter out on the water to see what higher rpms do..

after loosing my cdi box to a faulty switch I exercised due care on testing voltage to the kill wire. So to test I ran the motor with kill wire
disconnected. Results below.

With the ignition key in the off position, engine running or not.. .05 volts

With the ignition key in the on position, engine not running .05 volts

With the engine running and the key in the run position .5 volts..

With the engine running and the key in the off position .05 volts..

I did not see any continuity using my digital multimeter between the terminals at the engine side connector but still get the juice to the kill wire. The controls are new.


I read 12.67 volts at the battery and at the engine..

Switch leaking juice across terminals??.. its one of those sealed pods


read numerous tidbits on this.. CDI, the company cautions to test and sets a limit at 2 volts.. though I also read that any positive voltage
to the ignition box can cause damage....

right now i have a separate kill switch wired.. works great but its an extra switch and some extra wires.

anyone else test this stuff and have similar results?

is the rectifier update pushing more juice that the system is designed for?

is this commonplace and normal?? I just spent a bunch on replacing most of the ignition and charging and don't want to do it again..

Thanks in advance for your thoughtful replies
 
Voltage is good. Fully charged battery is considered exactly 12.65 volts. Do you get voltage at new ignition switch with kill wire disconnected? Do you get voltage at ignition switch end of kill wire itself....when only hooked up back at motor? Do you get the .5 volts at the switch box itself .....with kill wire disconnected? Now....you may find that you have to run a new kill wire between ignition switch and switch box. Neutral safety switch may have a part in this too.
 
The kill wire is connected to, is part of, the trigger circuitry. Trigger circuitry has bias voltage for the firing device (Silicon Controlled Rectifier) and other places, but these are milliampere current circuits. Like the water pressure at your house, if the faucet is off and you measure pressure, it's the static, non flowing, non resistive (voltage reducing in electronic circuit) potential. Turn on the tap and flow is determined by how far you opened the tap....aka the hole is small so the flow is low, aka restricted......in electronic circuits flow is determined by amount of resistance. So, just because you measured voltage, doesn't mean that you are hooked directly to the 12v supply. As others have said, it's normal.
 
thanks for all the input!

figured it was probably ok and normal..cannot say I really understand ghost voltage.. sounds like voltage thats there, we cannot control, its minimal, and so we ignore it...and you need an expensive meter to call it ghost voltage..

seeing the components get fried and spending the bucks to replace em makes me quite cautious... cdi box, trigger, rectifier, stator, now the choke too..

the tests were made at the end of the kill wire where it connects to the cdi box and not connected to the cdi box. Also tried disconnecting the kill wire from the mercury switch.. no changes.

manufacturer talks about making their ignition switch (the thing with the key) to minimize leakage.. so i take it there is some..

I read somewhere about putting an extra wire in a loom with one end to ground, the other to nowhere to pick up any emf induced current.. Maybe an interesting experiment.

Right now i am ok with the separate kill switch.. too much money on parts for the ignition system.. today a new stator and water test.. just glad to be running again with fishing season going on.
 
My comments were directed at looking back into the engine, from the ignition switch, with the voltmeter hot on the kill wire while attached to the ignition switch in On or Start position.
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Leaking through the switch contacts is highly possible on highly used rotary switches. The contacts are a printed circuit board with conductors protruding at specified points for the wiper on the switch to rotate around and make contact as designed. Over time silver/copper contact material migrates from terminal to terminal. You said your controls are new so forget that.
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Next comes "ground loops" where things are connected to different reference points and current flowing through the connection points cause an "error" voltage to develop. Your readings of 0.05V engine off, and 0.5V engine running, help to identify this as a potential source for your problem.

Think of the spokes of a wagon wheel and the battery - terminal is the hub. You don't get "ground loops" if negative terminals of electrical equipment are wired directly to the - battery terminal (reference point could be the battery - lead attachment point on the engine....usually engine block, not necessarily the battery itself), as are the spokes connected to the wagon wheel's hub. However, you remove half the spokes as an example, and "daisy chain" the system's grounds into another system's ground and that system's ground is the spoke then you have the voltage developed on the connected wire appearing on the "piggy back's" ground.

Another example of daisy chain syndrome is where the engine and associated equipment are referenced at the battery connection point on the engine proper, while accessories, lights, whatever have their neg wire tied directly to the battery....this setup surely reflects your change in voltage with the engine running. Connection back to the switch would be on the purple or red/purple striped wire, the "Switched" 12v distribution power coming from the ignition switch while in the On or Start position.......like you want all accessories OFF if you turn the ignition off so they are wired off the ignition HOT wire.

Check your battery - terminal. If you have anything connected to that terminal besides the ONE #4 or greater AWG wire going to the engine block, you have your source for "ghost voltages". To rid yourself of them, connect your accessories ground reference to the engine block where the battery - is connected.
 
You do realize that when engine is running and switch is in the on position that there is about 300V setting on the blk/yel wire waiting to go to ground when switch is turned off.
 
Right Pappy, agreed....For me it's a bit unnerving. Why? I know it's just milliamps, but for me, I would rather engineer to interrupt the power to switch box from stator....than short it to ground, in order to stop the motor......but then who the hell am I? I just try to fix 'em.....I never even went to college. It's way more convenient, with all the safety switches....to just make ground available.....to do the stop.
 
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Hard to beat something as simple as grounding a voltage divider feeding triggers into the capacitor dump switch (SCR or MOSFET). Yes sir it's milliamps and millivolts. Can't get much simpler than that.
 
I tested at the engine side of the kill wire while disconnected from the cdi box.. actual ignition switch is difficult. I kind of guessed about the phenomen you describe as ground loops. So that means that the coill grounds have the potential for feeding back to the cdi box as well?. they ground to the same place. Most of the grounds connect to the starter.. but the starter activator (solenoid) and the rectifier ground to the engine with wires to their mounting screws. That part of the engine sits in front of the carbs and is removeable. So if those bolts are not good and tight I could see some big problems.

I don't think i have any accessories pulling juice from the iginition switch purple. There is a small breaker next to the battery and a wire running to the dash. I am gonna redo all that.

Took the boat out and it runs. Noticed the sonar part of my lowrance couldn't get a reading for quite a while after going for a run. The transducer lead of course runs under the gunnel next to all the other stuff including my new kill wire.. So I took a guess and turned the sonar unit off prior to starting and running the outboard and subsequently stopping the outboard via the kill switch.. Turned on the sonar and no problems. I think Faztbullet expained that one below...300v.. Holly smokes...hopefully not my wire.. Makes me want to use a relay near the battery for the kill function.

I think its the keyed ignition switch as you described since the reading changes with the switch position.
 
Wow 300 volts.. So that explains my sonar going haywire when i hit the kill switch... All that juice created an emf that the tranducer cable picked up i think. With the sonar powered down during engine operation and kill then no problem.. Usually I am running the kicker so its not an issue less i forget the proceedure.

Seems like a relay located close to the battery would be a good idea. The ignition key switch powers the relay to ground the CDI Box..
 
I am no one to argue with Faztbullet. However. Killing triggers to the CDI or CDM is not to be done at the high voltage to which the capacitors contained therein are charged. The place to do it is as I said at the trigger input to the electronic switch (Silicon Controlled Rectifier...SCR, or Metal Oxide Silicon Field Effect Transistor....MOSFET) that dumps the capacitors. That voltage is no more than 5 and would be off a voltage divider from the batteries 12v supply.

Line Modulator Pulsed RADARS use the same principle and are triggered as I said. (Reference: 40 years in the business: Design, development, production, and maintainence!)

The term in the business is "Single point Chassis ground" and is necessary when you have sensitive receivers of high power RADARS and can't afford any unnecessary noise generated by ground loops.
 
Here is schematic....the keyswitch and kill switch ground the voltage from rectifier in switchbox to ground killing the capacitors input..
kill.JPG
 
Wow.. interesting stuff! Way over my head, though I am learning a lot. I have been working off the manuals, seloc and clymer, l and using the schematics. They show a black/yellow grounding the cdi box making contact to ground via the ignition (key) switch.. I try to load the page here and a pic of my engine. Thumb is on the old kill wire.. I done replaced all the ignition and the rectifier.. so thats stator, trigger, cdi box, and enhanced rectifier/regulator.. Leads 2 leads from the stator go to the cdi box, 2 yellow leads from the stator go to the rectifier to charge the battery..

heres a link to manual page and pic of engine.. Its a google photo album since i cannot upload here.. I really struggle with the photo sharing stuff... The wiring diagram is clymer b726 p.368

https://photos.app.goo.gl/Y1Da2duKqfq6QiA17
 
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As I said, "I am no one to argue with Faztbullet". Since you have the schematics and don't mind posting, would you post the trigger circuitry from the trigger coils including the switch and connection to the capacitors and HV coil firing the spark plugs? Since Mercury has established this "brute force" method of trigger control, I can't imagine what the rest of the circuit looks like.

On a person detecting the 300 volts at the black/yellow stripe wire in the control box, at the ignition switch terminal, with the pulses being in the microsecond region and the rest time being in the double digit millisecond region, a DVA adapter to a DMM would be required to measure it, I would assume. Amazing that ignition switches last as long as they do without shorting out in a marine environment. I suppose they last because the pulses are so narrow, the electrons in the switch material/surface contamination don't have time to get established before the pulse disappears.

Wikipedia lists energy (watt-seconds) consumed in the spark of a spark plug in general usage as 30 milliJoules (0.030 Joules). A joule being a watt second, aka a volt x amp per second. Amps depends on circuit resistance once the plug plasma ignites so it's an unknown without measuring. Volts are the actual volts across the discharging capacitor and the spark plug gap when firing (cap v - plug v) which are estimated to be in the hundred volt region, realizing that there is a high voltage transformer involved which transposes that 300V stored energy to 40kV (open circuit potential) and determines the reflected voltage during the discharge. Once volts and amps are established it's a matter of duration of the spark for dissipating the stored energy.

So looking at the energy stored in the capacitors, (½ CV exp2), with the 300V charge level, to store 30 mJ per pulse the caps would be in the range of 0.7 microFarads at 600vdc (double the working voltage).....not all that big of a cap to put in a little module (CDMs)

Since the schematic shows no resistance in the circuit the wiring resistance would have to be the only resistance along with the switch contact area. Assume 10 ohms for 20' of #20 AWG wire and 300V potential, seems the ignition switch has to resist the possibility of 30 amps for a few microseconds every time a plug fires.......not what I would call a reliable design.....but it has a proven track record for the application, has few components to fail and is inexpensive. What more could you ask for?

I am looking forward to the rest of the schematic if you have the time. I am 15 years retired and try to keep my brain functioning. Little skits like this help to ward off Alzheimers which I understand is encouraged by brain drain. Besides, what else is interesting while having morning coffee....surely not the news!
 
Excellent information, Texas. I certainly enjoy your posts. My Dad was an electrical engineer, built and managed 2 TV stations in the 1960's, 3 radio stations.....AM/FM, beginning in the late 1950's, then a TV cable system in 1964/65 in Hibbing MN, the first system north of the Twin Cities, then a broadband system, introducing fibre optics, in it's early years. I maintained the "head end" of the cable/broadband system until the family sold out to Mediacom in 2006.....against me and Dads vote. What we sold for 4 million in '06 is worth 20 million today.....with new equipment consideration and maintenance costs rolled in.....the sale proved foolish. Dad was also a student physics teacher at the University of North Dakota, but enlisted in WWII 1942. 4 years in the infantry in China took alot out of him, but still made it to 82.
Keep that mind sharp, my friend.....I understand what your saying. Many of my mentors here stay sharp the same way....I'm here to learn too.....and treasure the information.
 
Excellent information, Texas. I certainly enjoy your posts. My Dad was an electrical engineer, operating a coin machine/amusement business for 20 years, then built and managed 2 TV stations in the 1960's, 3 radio stations.....AM/FM, beginning in the late 1950's, then a TV cable system in 1964/65 in Hibbing MN, the first system north of the Twin Cities, then a broadband system, introducing fibre optics, in it's early years. I maintained the "head end" of the cable/broadband system until the family sold out to Mediacom in 2006.....against me and Dads vote. What we sold for 4 million in '06 is worth 20 million today.....with new equipment consideration and maintenance costs rolled in.....the sale proved foolish. Dad was also a student physics teacher at the University of North Dakota, but enlisted in WWII 1942. 4 years in the infantry in China took alot out of him, but still made it to 82.
Keep that mind sharp, my friend.....I understand what your saying. Many of my mentors here stay sharp the same way....I'm here to learn too.....and treasure the information.
 
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I will try to post the schematic.. Having hard time uploading without loosing clarity... So here it goes.. well its a freakin huge picture.. Pardon.. best i can do now



DXnHvOh.jpg


DXnHvOhm.jpg
 
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Excellent information, Texas. I certainly enjoy your posts. My Dad was an electrical engineer, built and managed 2 TV stations in the 1960's, 3 radio stations.....AM/FM, beginning in the late 1950's, then a TV cable system in 1964/65 in Hibbing MN, the first system north of the Twin Cities, then a broadband system, introducing fibre optics, in it's early years. I maintained the "head end" of the cable/broadband system until the family sold out to Mediacom in 2006.....against me and Dads vote. What we sold for 4 million in '06 is worth 20 million today.....with new equipment consideration and maintenance costs rolled in.....the sale proved foolish. Dad was also a student physics teacher at the University of North Dakota, but enlisted in WWII 1942. 4 years in the infantry in China took alot out of him, but still made it to 82.
Keep that mind sharp, my friend.....I understand what your saying. Many of my mentors here stay sharp the same way....I'm here to learn too.....and treasure the information.

Thank you sir. If I didn't have boat (and farm) related forums to put some gusto in my day, life would be much less interesting. You get to running with a forum over the years and develop a remote friendship/respect for the other folks sharing the experience.
 

Thank you sir for posting. i see that they used the same schematic to show both trigger kill (first picture) and a triggering device "activated" plus dashed line reference to the kill wire to the control box (second picture). The closed switch in the second picture would be the SCR or MOSFET.

Do you happen to also have a schematic of that circuit showing the link between the Trigger pickup coil (under the flywheel) and that closed switch? We have gone this far, just be neat if we could get "the rest of the story"....Paul Harvey, renown news caster/radio commentary.

I was on the CDI www this AM and I can understand why none of their schematics were posted. Course when you're selling modules, contents are proprietary and they do mention competition from abroad.
 
I will try to post the schematic.. Having hard time uploading without loosing clarity... So here it goes.. well its a freakin huge picture.. Pardon.. best i can do now



DXnHvOh.jpg


DXnHvOhm.jpg

Thanks for the effort. It does show the switch-box interconnection more clearly than the schematic in my 2015 revised manual for '94 and above 3 and 4 cyl. engines. The missing parts of your picture are in the manual and are easy to understand. I'll copy and add to my manual.
 
Dad was also a student physics teacher at the University of North Dakota, but enlisted in WWII 1942. 4 years in the infantry in China took alot out of him, but still made it to 82.
Keep that mind sharp, my friend.....I understand what your saying. Many of my mentors here stay sharp the same way....I'm here to learn too.....and treasure the information.
I was also searching for mentorship, but I discovered that sometimes even reading book summaries is more helpful (nothing bad to say).
 
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