Electrical problem I've been chasing for years. Help???
 

I have had this problem basically since I bought the boat 8 years ago. When I turn on my nav lights, all my gauges back up. That is, they all change their readings, oil pressure goes from 50 to 30, volts goes from 14 to 12, etc... Only thing that is not effected is the tach, I put that in myself several years ago. And when I turn on my docking lights, everything really goes down a ways. Been pissing me off for years, but I'm not that good at chasing bad electical problems. To me it seems I have a bad ground somewhere. I have the stereo running to it's own buss bar grounded to the block and have no trouble when I turn that on with the other systems. The previous owner re-wired the entire dash when he CNC cut a custom dash panal for it (which looks awsome by the way). But I'm not sure he got the wiring totally correct.

Any thoughts on where to start???

Sounds like you answered your own question there Mike! What i would do to verify its the ground is to try and run like an 8-10 guage wire from your batt to one of the ground wires in the dash and see if it still does the same thing.
From the sound of things the previous owner may have used the ground from the stock wireing harness in the boat that goes to the engine. Try and run a new gounding block or use that other one you have for you stereo/or tach. Hope that helps. :D

You definitely need to make sure that your ground is not only clean but that the wire/s providing the ground is at least equal to your power supply wire size. I would also recommend getting a higher output alternator with a smaller pulley to increase the output at all rpms. I had a similar problem and did this and it is much better now. Also the stock alt output is only about 55 amp but you can go up to around 100 amps.

I've got a high output alternator already. Still does it. So I know it's wiring related. What color is the ground in the Mercruiser wiring harness??? White? Black??

same deal
 

i posted pretty much the same question a while back and got good responses...the most consistant response was the "bad Ground" response...Wallys response to use a large gauge wire direct to the battery is one of those "duh" ideas that is the perfect way to isolate if it indeed is a bad wire harness ground wire..i will try it this weekend...

i will also say that i have observed this "gauge back up" phenomenon to a certain degree on two other boats i have ridden in recently so it may not necessarily be a problem. simply a reflection on the gauges that there is a voltage drop due to current flowing to the devices turned on....

it does bug me though.....

keep us posted with your results...it may help me also!!

gary

I had the same problem with a FourWinns and it was an inadaquate ground or a loose or dirty connection some where. All I did was run a seperate ground from the battery to the instruments and it cleared the trouble. My present Formula also showed low voltage and slightly elevated temps. Had 11.5 volts to the guages and 12.5 on the back of the ignition switches. Found a dirty connection on the hot side and now volt meters match battery voltage , and temps are back down to normal. I just couldn't believe both engines were running exactly the same high temps at exactly the same time!

all roads lead to the ground.....figuratively speaking that is ..cannot count the times I've chased down electrical gremlins only to find a poorly connected or inadiquate ground...

my wife is laughing as I type this... she has seem every time ...now when something wierd is happening with any kind of electrical gizmos I go straight for the ground wire


good luck

O.K. I know all my grounds are tight and clean, I just had the motor out and redid most of the connections. No improvement at that time. So, it has to be the ground from the gauges, but I have no idea what color wire to look for. The previous owner siad he used Mercruiser/Baja color codes, so I'm not even sure what wire to chase down!!!!

But, I did get my non-functioning bilge pump to work today. Turns out the hose clamp at the pump wasn't makeing a good seal so it wouldn't pump the water past about half way up the hose. Issue solved with a little silicone and a new clamp. Now, 1100 gph out that little puppy. Which is good, cause I have a leak I can't seem to solve either!!!! If it's not one thing, it's another!!!!

Now, out to find bad grounds!!!

Common ground wire in a home is WHITE, Common ground wire in automotive (boat) is black. I have see some green tho. When people are saying ground what is really happening is you are having a voltage drop. When you are turning on your lights the lights are getting there ground from your dash area. The greater load on the ground wire the greater the voltage drop. Running a larger wire from motor to the gauges should solve the problem. Remember the gauge is working off the voltage difference, As you increase load on ground voltage drop increase.

I just notice on my motor home last sunday same problem. Last week when I was going to lake in rain (lights on) I thought the engine temp was a little high. On way back (lights off) is was at its normal place. Sunday went to get fuel (lights off) & temp was norma, when I got home (dark & had lights on)I was starting to worry. I then turned lights on / off, temp would go up & down 25 degrees. So problem is just not boats.

I've been living with this issue for 8 years. And with my new motor I just want to know where my oil temp and pressure are, even in the dark!! So, what you're saying is that if I really want to get it right, I should run a new, larger ground wire for all the gauges, perhaps to a buss bar under the dash, to which I can run all the gauge grounds????? Man, given the dash layout on this boat, that's a LOT of work. Looks like spaghetti under there too (NOT the way I would have done it).

Oh, and the trouble shooting gun gets another notch. Figured out why my depth gauge kept turning on and off when on plane, loose POSITIVE wire at the ignition. Hit a wave, gauge beeped because it went off and came back on. Issure resolved. No more beeping.

So, that's two down, MANY to go.

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.

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.

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

Jon

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

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.

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;)

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

:) 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!! :rolleyes:

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)

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.

Tinkerboater

Then what you are saying is as the alt. increased or decreased the voltage the gauges will change their reading? When engine is not running battery voltage of a fully charged battery with no surface charge is aprox. 12.7v. When alt is putting out voltage is anywhere from 14.4-13.5 volts based on state of charge of battery, temp, & a few other varables.

I have been wrong before, but I thought when I turned on the iginiton the gauge would go to the lowest point if I had wire connected to sending unit or not. When I get in boat tonight I will have to try it.

HMmmm, I should have read Fouls original question more closely. Tinker is right. But how would turning on the Nav lights affect the engine guages? They are effectively a seperate circuit. ?? Id like to drag my Simpson over there and have at this one. Sounds interesting.

The guage cluster uses power fed from the key switch. And the nav light s probably feed from the same power wire or fuse block.The slight difference in voltage from when the engine is off to when it is on will not usually make a difference in the guages. With everything turned on FOUL probably has 9 to 10 volts at the guages instead of 13.

TURBO -- when I turn on my ignition keys my guages read what the pressures and temperatures are at that time. Same for drive possition and volts. Fuel level reads the amount of gas in the tank also. The engine doesn't have to be running for all your guages to work.

Tinker- I agree with when engine is on or not gauges read what the condition is at that time. What I was trying to say is (& did not do a good job at it), take the oil pressure gauge, when key is off needle could be anywhere on scale. When key get turned on with engine off gauge will go to "0" oil pressure. I am thinking that gauge goes to "0" if the sender wire is connected or not. If I am correct, then the gauge does need ground. Otherwise gauge would just stay where ever needle likes sitting at if the sender wire is off.

formula31- Wish boat was closer to me so I could see exactly what problem is.

Foul- Do you have a volt meter on dash? When lights are turned on or off what is it showing in voltage?

Turbo --- the sender wire is the ground. If you remove the wire it will read 0 --if you short it to the engine block ( ground ) it will read full scale. This same process works with the engine temp also. The sender has a reverse acting variable resister in it -- as the temp or pressure goes up the resistance goes down ( more ground) gas tank sender works the same way.

Tinkerboater - Just got home & checked out my gauges (eliminator brand??) Needle on water temp was at 200+ mark. disconnected wire going to water temp sender. Turned iginition on, gauge then went to all the way down. Reconnected temp sender wire & gauge moved up to 100 (temp in garage). I did not disconnect ground wire at gauge because too hard to get to. If the ground was not used by the gauge at all, the gauge would not have gone to the lowest point with the sender wire disconnected when power was applied to gauge. I am not saying all gauges need ground just ones I have in my boat.

Most boats with stock guages--The needle will be at 0 with the power off.

Waterfoul;
In your earlier post, you said your navigation lights were causing the problem, in a later post, you said your docking lights. Which is it? The nav lights don't take much current and your problem is probably in the plus wire to the dash (per tinker boat). If you have your docking lights on the dash curcuit, you are overloading the wire and the voltage starts to drop. You need to run an independent circuit with sufficient capacity.

Foul-
I was trying to give you a general troubleshooting technique- it does not matter if you have fuses or breakers. Start at the end and work your way back to the battery. Whatever you do, don't let the smoke out, it makes all that stuff work.

I have an issue of hot boat(?) about 4 years old with the foul in it!

Tinker-
You are probably right, but I would still do a complete check of the system. I have seen bad connections do some strange things- and he may have more than 1 problem.

It would be kinda nice if you told us what you found. After all, a lot of people responded with suggestions. You don't even answer back. What is with that?

Dude, I have a busted gimbal ring I'm trying to get fixed at the moment. The gauge issue unfortunately is second at this time.

My plan though is to run a new ground wire forward to the nearest and easiest gauge to reach to see what that accomplishes. I'll post with any results.

Mike

i was not the original poster but i did ask a similar question a while back and have a similar issue...

so far i have only done the neg side...ran a #10 from batt terminal to dash terminal block ...no real change...
i also added a relay setup from rex marine to the hatch actuator (which ran really slow). this helped tremendously...this improvement suggests that indeed it is a positive side issue with the dash gauges...
my question...

from where does the +12vdc wire start back in the engine area that goes to the "run" position on the switch...this is the next one that i will replace...

thanks

gary

Of course it depends on your boat. Main 12+ comes from battery to the starter post, there should also be a small wire #10?? that is connected to the lug at the starter. Wire then goes in wiring harness on engine to big round plug. From there it goes thru wiring harness up to the dash.

My hatch motor also runs really slow this season. I have to help it up the first several inches too. Hmmm....a positive issue you say?? Have to check that out too I guess. But first, I have to get my transom assembly fixed.