Voltage differencel between Display on volt gauge vs. read per multimeter@ batteries.

Okay, so pretty much the whole time I've owned the boat the volt gauge on the dash would read really low. And the digital voltage reading on the perfect pass would be about the same as the volt gauge on the dash.

So, today I got the following readings:

Voltage display per PP or Volt Meter on dash with the boat idling or at higher RPM's fluctuated between 10.5 and 11.

Voltage measured at the batteries with the engine on was between 13.7 and 14 depending on which battery I had the perko switch pointed at (one was stronger than the other because it'd been running the stereo with the engine off for a lot of the evening). Voltage at the batteries with the engine off were around 12.5 if I remember correctly.

So the reading per my handheld volt meter at the batteries is exactly what I'd expect. But the reading per the dash gauge and per the perfect pass were really low and always have been since I've had the boat.

Has anyone ever come across this before? My guess is that there is a poor connection somewhere on the Dash's wiring harness.



EDIT: I did some more testing just now. With the key off, the hot wire to the ignition switch was reading around 12.68 or so. However, when I turned the key to the on position (dash lights and perfect pass being the only things taking voltage, the reading on the hot and the switched terminals of the ignition dropped down to 11.8 or so. furthermore, I would get that 11.8 reading at most of the fuses at the fuse block. And the digital readout on the Perfect pass was actually down at 9.8 volts. I was getting a similar reading checking the voltage at the red wire near the servo motor (around 9.8 volts).

I have two good batteries, and I've just replaced the power wires that connect the batteries to the Perko Switch with brand new terminals and zero gauge welding cable. Likewise I have a brand new zero gauge with new terminals for the ground to the block and for the neg that connects the two batteries.



So, my gut is telling me to replace the ignition switch...

Any insight? Run across this before? Anything else I should test?

I had the same problem. Ran new 10 gauge wire to the fuse block and ground block and it fixes it. Make sure all con connections are good and clean.

I have the same problem but not as bad, reads about 1-2 volts lower on the dash than at the batteries. I get 13.x at dash and I believe 14.6 at batteries with engine running. Probably feed wire or ground, I need to clean or replace I'm sure.

If i was working on this boat, here is what I would want to know. With all electrical loads off, but battery switch on, what is the voltage:

Battery post
Common post of the switch
Helm BUSS/Fuss block
B+ side of key switch

With the key switch on:

Battery post
Common post of the switch
Helm BUSS/Fuss block
B+ side of key switch
Switched output side of key switch
any suspect devices such as volt gauge an PP

With engine running:

At alternator main post
Battery post
Common post of the switch
Helm BUSS/Fuss block
B+ side of key switch
Switched output side of key switch
any suspect devices such as volt gauge an PP

If you find you have a voltage drop from one point to the next, you are getting close. But take note of where you clip the ground lead for the meter. A poor ground cable or connection will result in low voltage same as a problem on the B+ side will. If you have low voltage under the helm, then move your meter's ground lead to the battery ground post directly and retest. if voltage no is higher, the problem is with the ground side feeding where ever you had the meter lead hooked.

It could be as simple as the wires running to the helm area are a tad overloaded. With the addition of the modern amenities they should be placed on their own separate circuit from the battery to a fuse block and to the accessory. This way the factory stuff remains clean and tidy with no future issues due to poor workmanship or wiring hack jobs.

Quote:

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Originally Posted by villain

I had the same problem. Ran new 10 gauge wire to the fuse block and ground block and it fixes it. Make sure all con connections are good and clean.

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Good to know.

Quote:

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Originally Posted by cadunkle

I have the same problem but not as bad, reads about 1-2 volts lower on the dash than at the batteries. I get 13.x at dash and I believe 14.6 at batteries with engine running. Probably feed wire or ground, I need to clean or replace I'm sure.

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Always something with these boats.

Quote:

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Originally Posted by Wylietunes

If i was working on this boat, here is what I would want to know. With all electrical loads off, but battery switch on, what is the voltage:

Battery post
Common post of the switch
Helm BUSS/Fuss block
B+ side of key switch

With the key switch on:

Battery post
Common post of the switch
Helm BUSS/Fuss block
B+ side of key switch
Switched output side of key switch
any suspect devices such as volt gauge an PP

With engine running:

At alternator main post
Battery post
Common post of the switch
Helm BUSS/Fuss block
B+ side of key switch
Switched output side of key switch
any suspect devices such as volt gauge an PP

If you find you have a voltage drop from one point to the next, you are getting close. But take note of where you clip the ground lead for the meter. A poor ground cable or connection will result in low voltage same as a problem on the B+ side will. If you have low voltage under the helm, then move your meter's ground lead to the battery ground post directly and retest. if voltage no is higher, the problem is with the ground side feeding where ever you had the meter lead hooked.

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Makes sense. Checking all those spots I'm sure will uncover something.

Quote:

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Originally Posted by DAFF

It could be as simple as the wires running to the helm area are a tad overloaded. With the addition of the modern amenities they should be placed on their own separate circuit from the battery to a fuse block and to the accessory. This way the factory stuff remains clean and tidy with no future issues due to poor workmanship or wiring hack jobs.

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Well, honestly the only things added are:

1. Depth Gauge
2. Perfect Pass in place of one of the speedos
3. Wetsounds WS420sq instead of a head unit
4. LED lights replaced the Court Lights (this probably is a decrease in load vs OEM)

So, it's not like I'm taxing the system with much more. Sure the PP might be a little, but can't be that much. All my stereo amps are wired such that they're triggered by a remote turn on lead and in turn pull their power with a straight run from the Perko Switch (just next to the batteries).

But Yeah, I get what you're saying. I'm sure that there might be some new runs of upsized wire in my future.

Quote:

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Originally Posted by villain

I had the same problem. Ran new 10 gauge wire to the fuse block and ground block and it fixes it. Make sure all con connections are good and clean.

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This may be a dumb question, but I haven't stumbled across the 'ground block' yet. I would think that somewhere under the dash there's a place where the grounds are accumulating, but I haven't noticed it yet. I'm sure that I just need to start tracing the ground wires off the gauges or the switches...

At least the fuse block is obvious. Is that powered by a run from the starter relay terminal?

My ground block is right under the fuse block. And it used to get power from the starter relay. I ran power right from the battery switch.

Do a voltage drop test from your main feed wire and the ground wire. Connect a volt meter from the battery + to the hot wire under the dash and turn on some load, sounds like turning the key on will suffice. If you have a voltage reading on the meter it is telling you you have a large resistance to electrical flow in that circuit. Same thing with the ground side. What you will be reading is current that is flowing through the volt meter instead of through the circuit, electricity is lazy that way, always looking for the easy way out. If it weren't so useful, I'd swear it was a supporter of our current government. But back to the point, you want little to no voltage to show on the meter. If you do show a reading then try and isolate where it is by doing the same test at different points. It is really quick and easy and foolproof.

You are looking for less than .20 volts DC on your circuits, with lower loads that number should be lower still. anything over that have too great a drop. This test can be used to check battery terminals as well, one lead to the post, one to the clamp or wire coming off the battery. You should see nothing at all there for voltage, even under a high load, like cranking the engine. The higher the load, the better this test is. You must have current flowing for this test to be valid.

Quote:

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Originally Posted by villain

My ground block is right under the fuse block. And it used to get power from the starter relay. I ran power right from the battery switch.

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Huh, I looked again tonight and I can't even find a ground block in the dash area. Wierd. I know they have to go somewhere.

FWIW, I tested voltage on the ignition switch and it doesn't seem like it's dropping. I might just replace it anyway, because a 3 position 3 prong switch is damn cheap. Maybe I can find some time tomorrow night to add a new run of power/ground from the battery over to the area by the dash. The power is easy because the fuse block is obvious. Just wish I could where all those grounds are going.