Voltmeter wiring: would this work?

axeslinger1957 · Jun 17, 2009

I have obtained a voltmeter because it appears it would be a good idea, based on my experiences, to be able to monitor the voltage output of the battery that starts my motor. I have read here that the voltmeter is wired into the ignition switch so that it is not on all the time. OK, that concept is reasonable. However, doesn't that mean you can only get a voltage reading when you are attempting to start the boat? That might be a bit late to find out your voltage level is low. Plus, I have no freaking idea how to achieve this hookup.

I have a different take on it. That means there must be something wrong with my idea, however, I'm going to ask anyway: What if one connected the voltmeter directly across the battery all the time (with a fuse, probably?) -- in series with a momentary-contact pushbutton? That way, I could get a battery measurement whenever I wanted. This is too good to be true and I'll set my boat on fire if I try it, right? OK, if so, how does one determine ignition switch wiring?

Phantom_II · Jun 17, 2009

Re: Voltmeter wiring: would this work?

The problem I see with what you're suggesting is that your voltmeter will only work with the pushbutton switch depressed so you won't know what your alternator is doing while cruising around.

The normal method is to connect it to the ignition switch so it reads all the time while the engine is running. If you want to spot check your battery voltage, just turn the ignition switch on for a moment, read the meter, and turn it off again.

Not really more difficult to turn a key than to push a button.

However, if you really like the pushbutton switch idea you can still use the wiring at your ignition switch. There should be three terminals at the switch. One has power all the time, one has power when the switch is on, and on has power when the switch is turned to the start position.
Connect the voltmeter between the "on" terminal and ground, then run a second wire from the power terminal through your pushbutton switch to the meter.
That will give you normal voltmeter operation and still give you a pushbutton spot check.

axeslinger1957 · Jun 17, 2009

Re: Voltmeter wiring: would this work?

Phantom, thanks for the reply! That's more than I was looking for. I like the way you think!

One more question, if you please: Would I use a DVM to determine which ignition terminal has "on" power and which has "constant" power?

Phantom_II · Jun 17, 2009

Re: Voltmeter wiring: would this work?

axeslinger1957 said:
One more question, if you please: Would I use a DVM to determine which ignition terminal has "on" power and which has "constant" power?

That would be the simplest way.

Read between the terminals on your ignition switch to a convenient ground point.

One terminal will have 12 volts, the other two will have zero.
Then turn your ignition switch to "on"
Now there will be two terminals with 12 volts on them. The terminal that went 'hot" when you turned the key on is the one you want to connect your voltmeter to, and the one that was hot when the switch was off is the one you want to connect the pushbutton switch to.

bruceb58 · Jun 17, 2009

Re: Voltmeter wiring: would this work?

Problem is that when you push the button, you will be turning on the entire ignition system as well...just like turning on the key. Sure you want to do that with a pushbutton? If you don't mind that, then no problem.

Splat · Jun 17, 2009

Re: Voltmeter wiring: would this work?

Personally I have mine wired into my accessory switch, which also controlls my fishfinder, and my 12v power outlets.

When ever I'm out this switch is always on for me, so I can monitor the battery voltage. I can also kill it when I get back to the ramp so it bot sitting there eating up juice.

If your going to hook to the ig switch, and a pushbutton you need to install a diode between the posative terminal on the volt meter and the ignition switch.

Bill

flargin · Jun 17, 2009

Re: Voltmeter wiring: would this work?

Phantom, great simple idea.

I agree with bruce and splat that may not be optimal, but it sounds like it works with Axe slinger's knowledge.

I think the easiest, and least complex is to put the key in, turn it one click, and turn it back off. but I like simple.

axeslinger1957 · Jun 17, 2009

Re: Voltmeter wiring: would this work?

Flargin said:
Phantom, great simple idea.

I agree with bruce and splat that may not be optimal, but it sounds like it works with Axe slinger's knowledge.

I think the easiest, and least complex is to put the key in, turn it one click, and turn it back off. but I like simple.

The button was a crutch to compensate for my total lack of knowledge regarding the ignition switch. If I can actually get to the terminals, I can figure out their function and implement the "click to test". However, the ignition is the "start and push to choke" kind. It's packaged with a throttle lever and a choke lever. Any ideas how to expose the ignition switch?

flargin · Jun 17, 2009

Re: Voltmeter wiring: would this work?

axeslinger1957 said:
The button was a crutch to compensate for my total lack of knowledge regarding the ignition switch. If I can actually get to the terminals, I can figure out their function and implement the "click to test". However, the ignition is the "start and push to choke" kind. It's packaged with a throttle lever and a choke lever. Any ideas how to expose the ignition switch?

I think what this says is you have a key, when you turn it one click, then to start it you push the key in, and turn it one more turn to get the starter to work, is that correct? I think that is normally an outboard installation. what make /model is it?

I am assuming you currently do not have a volt meter on your system and that is where your question is coming from. If so, they are the easiest to install. Look at the stickies and you will see a diagram.

but, to help explain, on the back of the key (normally you can climb under to take a look) there is at least 3 lugs (outboard has more at times) one is direct from the battery, one is the "Ignition" and that goes to +12v when you click it once. On Mercruisers, this is a purple wire.

You would tap off of this lug, bring the wire to the + of the voltmeter, and take a black line form the - on the voltmeter back to some return line/ground line (normally Black)

If this still does not help, show us some pictures and we can help walk you through it.

Sorry if I am having a tough time figuring out exactly what we can do to help directly... but we never give up... that is the cool part

bruceb58 · Jun 18, 2009

Re: Voltmeter wiring: would this work?

Splat said:
If your going to hook to the ig switch, and a pushbutton you need to install a diode between the posative terminal on the volt meter and the ignition switch.

I wouldn't think you would want to do that either because you will show 0.7v low when the ignition is on.

bruceb58 · Jun 18, 2009

Re: Voltmeter wiring: would this work?

Flargin said:
I think the easiest, and least complex is to put the key in, turn it one click, and turn it back off. but I like simple.

Me too...I subscribe to the KISS principle.

Splat · Jun 18, 2009

Re: Voltmeter wiring: would this work?

bruceb58 said:
I wouldn't think you would want to do that either because you will show 0.7v low when the ignition is on.

Yea i forgot about the volatge drop issue. I was only thinking about how to eliminate the hotwire issue.

you got me there.

Bill

Phantom_II · Jun 18, 2009

Re: Voltmeter wiring: would this work?

If you can't physically access the terminals on your ignition switch, an alternative would be to attach the positive lead of your voltmeter to the red wire on any of your existing instruments, such as fuel or temperature.

Both of these indicators generally require 12 volts from the ignition switch to operate and are usually easy to access.

axeslinger1957 · Jun 18, 2009

Re: Voltmeter wiring: would this work?

Phantom_II said:
If you can't physically access the terminals on your ignition switch, an alternative would be to attach the positive lead of your voltmeter to the red wire on any of your existing instruments, such as fuel or temperature.

Both of these indicators generally require 12 volts from the ignition switch to operate and are usually easy to access.

Heh-heh, wal, ya see, pilgrim, it's like this: they AIN'T no other instruments. I ain't got none. This voltmeter is the first. I'm not saying I can't get to the wires, I'm just saying I don't know how. If I remember right, the unit says something like "Evinrude Power Pilot" on the side.

flargin · Jun 18, 2009

Re: Voltmeter wiring: would this work?

can you get to the key switch back? if so, we can help you there.

Are there any wires you have access to?

Pictures?

axeslinger1957 · Jun 19, 2009

Re: Voltmeter wiring: would this work?

Flargin said:
can you get to the key switch back? if so, we can help you there.

Are there any wires you have access to?

Pictures?

I'm out of town right now. When I get back, I'll investigate access to wires and get pictures.

Silvertip · Jun 20, 2009

Re: Voltmeter wiring: would this work?

Another simple project made overly complex. A voltmeter does not need to be wired to the ignition switch. It is installed like any other gauge and can be wired to the "I" and "Ground" terminals on any other gauge. You don't need to go near the igntion switch which seems to cause folks even more grief and has the potential to screw other stuff up. You also don't need a separate switch. Since the gauges are active only when the key is in the RUN position, the voltmeter will also be active only when the key is in the RUN position. Why flip a separate switch to get a voltage reading when all you need to do is flip the key to RUN to get the same effect. There is no need to have a "continuous" voltage reading when the engine is stopped.

flargin · Jun 20, 2009

Re: Voltmeter wiring: would this work?

not trying to make it complex, as I read the thread, I think the key gap here is he has nothing to use, he has no other gauges. His previous post:

Heh-heh, wal, ya see, pilgrim, it's like this: they AIN'T no other instruments. I ain't got none.

Silvertip · Jun 21, 2009

Re: Voltmeter wiring: would this work?

In that case the +12 volt input to the gauge goes to the "A" terminal on the ignition switch and operation is the same as in my previous response. And just in case this is a tiller steered boat or one without electric start, then break out a spool of wire and use the separate switch.

axeslinger1957 · Jun 22, 2009

Re: Voltmeter wiring: would this work?

Silvertip said:
In that case the +12 volt input to the gauge goes to the "A" terminal on the ignition switch and operation is the same as in my previous response. And just in case this is a tiller steered boat or one without electric start, then break out a spool of wire and use the separate switch.

Guys, I'm not trying to stir up any trouble here. Really! Silvertip, the issue is that my ignition switch is inside of an Evinrude Power Pilot remote control. I happened to ask about how one might open it up when I was at a marine repair this past weekend. I knew the thing was old. Everything on my boat is old. The guy at the store actually SNORTED and curtly replied that they "didn't work on anything that old". See, the problem is that I understand electricity and electronics very well, but I have little "wrenching" experience. The only thing I could find out about disassembling the Power Pilot is that you are supposed to be careful not to lose some spring when you open it. The other thing I know is that I have three cables coming into mine. I am willing to bet two of them have to be hot and ground. I am also willing to bet that cable 3 is actually a cable bundle that leads to some kind of wire bus on the motor. Another issue is that there are many screws on that thing. It looks like you could take the top and/or either side off. I have not figured out the "least invasive" way to look at the ignition switch yet.

Voltmeter wiring: would this work?

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