Turbojack

Yes, buss bar would be good way to do it but I bet if you ran some #8 from the engine to any gauge's ground that you can get to will make problem go away. Just leave other grounds there also. Not best way to do it but I would not worry about burning down / up boat.

Tinkerer

If all your gauges are going down when you turn on your running lites the problem is probably a bad hot wire connection or a hot wire that is not big enough to handle the load. The oil pressure and engine temp guage don't use batterie ground - they get their ground through the sending unit. If the voltage drops to the instrument cluster all the guages will read low. The easy way to test this is to run a temporary hot wire from the batterie to the hot connection on the guage cluster with the engine and lights on - if they go up to normal then that is the problem.

Audiofn

Foul give me a call and I will help ya out with this one as much as I can.

Jon

Bulldog

Foul-

Remember Rule #1 of electrical systems: There is only 1 true ground!!!! (forgive me supercrash). This is at the negative POST of the battery. All readings MUST be taken with the negative voltmeter lead connected directly to this point.

Rule #2: there is only 1 true positive point- at the positive POST

Use the procedure below- it only takes a few minutes and eliminates guesswork.

First Connect the Voltmeter negative lead to the battery negative terminal, and check BATTERY voltage at the battery positive POST. It should read about 13 volts.

Now verify positive side connections:
You will take all voltage readings with the positive lead. All readings should be near the battery voltage reading of 13 volts.

Now turn on the key- instruments appear OK. Measure voltage at the instruments. The voltage reads 11.5 volts. The voltage drop (1.5 volts) is due to current flowing through the resistance somewhere in the positive circuit.

Now, turn on the lights. They are also connected on the bad side of this bad connection. This means you are pulling more current through the bad connection, and the voltage drop will now be greater. In this example 5 volts dropped- the meter will now read 8 volts.

This sudden voltage change causes the instruments to change readings instantly.

Next place to check is at the fuse panel. Assume the voltage behaves the same. This means the problem is upstream from the fuse panel.

Measure voltage at the switch, on the terminal that feeds the fuse panel- same voltage readings occur.

Drop back to the supply lead from the battery- 13 volts all the time- bad switch or connection.


Now, what if you measure at the battery, instruments, etc. and find 13 volts. Turn lights on- 13 volts, with crazy instrument readings. Haunted boat maybe???

No- bad ground. It's the same thing, only different.

With bad grounds, you will measure voltage on the ground terminals. A good reading is 0 volts.

Start taking voltage readings again, at the instruments, but measuring for voltage on the ground terminals.

With an identical bad connection on the ground side, you would read not 0 volts, but 1.5 volts. Turn on the lights- the voltage at the ground is now 5 volts. The instruments go nuts.

The instruments change, because you have 13 volts at the positive terminals and 5 volts at the negative terminals. th voltage difference of 8 volts is what the instruments get.

Just work your way backwards from the instruments to the battery. When you read 0 volts, you have isolated the bad ground connection.


good luck
Bulldog

formula31

What Bulldog said. I just ran 2 new #6's from my house battery to 2 new buss bars under the dash and all new fuse holders and fuses and all new wires to the switches and gauges. Problems gone. Also did away with all spade connectors and only using ring connectors now. Was a pain but electrical problems gone. I think most of mine was corrosion on the fuse holder clips.

28Eliminator

Bulldog is absolutely correct. Good job on the trouble shooting procedure. If you do what Bulldog said, you should be able to isolate the problem in less that an hour.
Some times you won't be able to find where the problem is, but you run a new wire to replace the bad one. Some riggers may splice a wire in the middle of the front and back of the boat and the connector can have a bad connection or get corroded.
Happy hunting

Waterfoul

Couple of issues to me using that method. No fuses. Previous owner installed circuit breakers for all the switches and "stuff." Second, it is almost impossible to get to the back of the gauges. If I really wanted to do this right, I'd just re-wire the whole damn thing. But, it's too late in the season for that now. I'm thinking I'll try the one big ground to the nearest gauge I can reach, and re-wire the docking lights independent of everything else (it's own + and - wires).

Mike

blown formula

What formula 31 said!! Put in new buss bars & #6 or #4 wiring back to the main ground block off the battery or direct from the battery. This goes for positive leads also. It is possible that the grounding problem you have is not a "bad" ground, but either a ground loop or grounding thru a gauge or sensor. I would start with a new ground CABLE under the dash & wire all gauges , switches & lights to it. It will probably solve the problem. The world's worst problems are either woman or wiring related!!

Turbojack

Go with the # 8 or 6 to where you can reach a ground wire. The gauges are working off the difference between the ground it is getting from the sending unit & the ground wire you have connected at gauge. I thing bulldog said it best by if you put a volt meter between the ground at the gauge & ground at the engine you should get a "0" reading. The input voltage to the gauge should not make a difference in the readings (except the volt meter)

Tinkerer

I repeat --- it has to be a positive connection problem. The oil pressure and water temp guages DON"T use a ground wire at the guage for anything other than the ilumination . If those guages are droping when you turn the running lights on than the problem HAS to be with the positive connection between the guages and the batterie. I work with MUCH more complex electrical systems than this everyday. If the engine turns over easily than it has a good ground. The oil pressure and water temp senders get their ground from the engine. That engine ground then goes through a varible resister in the sender and then to the guage. The lower the resistance the higher the reading on the guage.