gas gauge no work ?

[badbird]

Got my boat out of storage this week end....trying to figure out why the gas gauge is not working :confused:
I have 12volts at the light for the gauge....and 10 volts to gauge....when i turn the key on i see a slight movement from the gauge,but in the wrong direction....I check for voltage at the sending unit,no voltage ?

I will search for a wiring diagram.

Any help greatly appreciated.

Thanks

[zelatore]

First place I'd look would be the connections at the sender. Especially the ground as it's just a push-on spade terminal on a lot of them.

[badbird]

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The connections at the sender are good.....we have no voltage at the sender.

Going to search for that diagram.....I have seen one here before.

Thanks

[mattyboy]

Verify ground at both the sender and the gauge. Disconnect the sender then short the sender term on the gauge to ground on the gauge, should peg full. To check the ground at the tank use ohm meter should show a dead short from gauge ground to tank ground on a dig meter should be OL or all zeroes

[mattyboy]

Sorry forgot the key needs to be on to check the gauge remove the sender wire from the gauge then short the sender term to the ground on gauge

[mattyboy]

If that test passes the gauge is good if not the gauge is bad

Next if gauge is good reconnect gauge remove the sender wire and ground to sender at the tank with key on short those two wires gauge should peg if it does sender bad if it doesn't then there is an open in one of those two wires each wire will need to be tested for continuity

[badbird]

Thanks for the replies Matt :)

I think one of those wires must be open.....as there is no power at the sender,...so the two wires at the sender,one red and one black...should go up to the gauge...red and black?
If the ground at the sender is bad could i not just run a jumper from batt neg to check it ?

Thanks matt....i'v been working on the boat all weekend...looks great.
Had to fix the lights and blower...just need to get this sorted out.

[mattyboy]

usually what happens after winter layup there's a ground wire that didn't get re connected to the battery


the ground in the system should be common engine block to neg of the battery to every ground needed on the boat if it is a metallic tank the tank should be grounded as should the filler neck

[Tidbart]

You shouldn't have voltage at the sender. The gauge is reading an impedance across the terminals of the sender.

Also, you have 2 wires a the sender, one is pink, the other is black. Don't mistake the pink one as a red wire that would have 12 volts to it. It is a signal wire.

If you need a sender, let me know.

B

[badbird]

Thanks for the help guys....I got it figured out tonight....both wires to the sender are bad :frown:

I jumped the gauge out like you suggested Matt....gauge good ;)

Thanks for the no voltage at the sender tip Tidbart :D the sender shows 70 ohms resistance and that's 3/4 full with with bad wires jumped out.

So now I need to run two new wires from sender to the gauge....if u guys have a good route for me please pass it on.

cheers

[badbird]

New wires in and working :beer:

I will check to see if tank is grounded tomorrow Fixx....and why does the tank need to be grounded ??

thanks

[joseph m. hahnl]

I will check to see if tank is grounded tomorrow Fixx....and why does the tank need to be grounded

All metal should be bonded.But primarily the gas tank and filler port are bonded to prevent a static charge igniting fuel vapor while filling






http://www.boatus.com/pressroom/previewImg/hiRes/474.jpg

[badbird]

GOT YA.....:kaioken:so if its not grounded,could I ground it with a jumper from the ground wire at the sending unit ?

thanks for the heads up.

[Just Say N20]

Attached a ground wire to the fuel fill. Run that wire to the ground on the tank.

[Tidbart]

Bad,

As far as the ground goes, no, you can't just attach a jumper to the black wire of the gauge. The black wire is not a grounding conductor, it is a grounded conductor. See this drawing. 71045

There is usually a third, green conductor (ground), attached at the sender to one of mounting screws. Look around the top of the tank and see if there is one and see if it is attached elsewhere.

Also, heed what Fixx said about the fuel fill ground.

B

[badbird]

Thanks Tid...I'm with you on the jumper thing,I was thinking about it today....I will have to run a separate wire and attach to sending unit mounting screw,thx for the link.

Fixx I'll check for the wire at the fill...thanks

Neil

[badbird]

Well thanks for the lesson on grounded conductor and grounding conductor :wink:

good news is checked the fuel fill...big wire from fill to tank..checked it with meter,were good
All dash lights working,3/4 on the gauge :yes:

New flush valve next....maybe fire her up this weekend.

thanks everyone

[zelatore]

Careful there - those green 'grounding' wires are not grounds, but bonding wires. What's the difference you say? Well, not much and a whole lot - bonding should tie all metal things in the boat together and protect them via the on-board zincs, but shouldn't be used as a current carrier for electrical devices as that's a good way to eat up metal and zinc.

Sounds complicated, but basically remember not to use the green wires in place of the black wires - every circut needs it's own black ground wire along with it's power suppling wire.

Some reading I stole from marinesurvey.com:


There is only one point where the DC side is grounded, and that is at the battery. It, too, is a "free floating" system in which nothing is ever grounded to any metallic part of the vessel, most especially not the bonding system. Just like a car sitting on rubber tires, completely insulated from earth potential, the battery itself provides the negative potential.The bonding system, also green wire, has nothing to do with electrical systems. Underwater metals are simply wired together to equalize differences in potential of different kinds of metal. Nothing should ever be grounded to the bonding system. Unfortunately, some people don't understand this and use it to ground electrical equipment, occasionally with disastrous results.
Bonding Systems
Bonding simply means wiring all the boats underwater metals together. This is done because of the galvanism caused by the different metals. By wiring them together, the differing potentials are equalized. Bonding does not solve problems of galvanism or electrolysis, but it does spread the the flow of current around over more metal, so that 1/4 volt or so won't cause any damage. Whereas if that 1/4 volt were going to one small seacock, it would probably eat it up in a hurry. In other words, bonding lessens the effect of small amounts of current. On the other hand, it also spreads it around to all underwater metals so that higher currents end up damaging everything.

[Tidbart]

Not to nitpicky but, for clarification,
"Careful there - those green 'grounding' wires are not grounds, but bonding wires." Grounding and bonding wires can both be green. The green one on the tank is a grounding wire, but not a ground. Some may say it is a bonding wire, but not the ABYC.

"every circuit needs it's own black ground wire along with it's power supplying wire." I am sure this a typo, but, there is no black ground wire. It is the negative conductor of an electrical circuit. Too many people refer to the black wire as a ground, not just in boating but in the ac world also. In the ac world, there is a neutral conductor many mistakenly identify.

I know this seems trivial but the semantics of this can and does lead to mis-wired circuits and damaged equipment, and sometimes injuries and death. The latter is not that likely in these smaller boat.

If it helps any, here is a generic boat wiring diagram.

B

71060

[badbird]

Thanks again for all the help....I was reading my Volvo repair manual,it said the fuel line from the tank to the engine should provide a continuous metal to metal contact for proper grounding.If any part of this line is non metallic material,then a copper wire must be run to bridge the non metal material.the power train provides a ground through the engine and drive shaft,to the propeller in the water.

I know my fuel line at the tank is rubber,and rubber at the fuel pump.

should I run this wire also.

cheers

[mattyboy]

a few things to remember one being things have changed a bit as far as recomendations from years past. tank materials, grounding, clamping, the fuel itself.

the steel tank in my 16 didn't even have a lug for a ground. the requirement for the filler to be grounded came after a few mishaps I am sure again my 67 didn't have the filler neck grounded.

I would think that as long as the tank is grounded to the block, ground is ground the routing of the wire doesn't matter depending on how the fuel line is routed running that wire with the fuel line might prove quite difficult. some of the older classics only had single hose clamps on the filler hose that needs to be double clamped now.

I have a few different era volvo manuals some things changed some didn't as time moved on.

a rainy day reading material would be the uscg regs on fuel systems that can be a real thriller owning an early classic.

I never really metered out the drive and the transom plate but i would imagine with the plastic bushing on the drive suspension and rubber hubs in most volvo props it might be difficult to find continuity to the block on the drive case or prop.

my new setup has the tank and filler gounded it also has the sender grounded on a seperate wire, the sender changes resistance to ground in the circuit the gauge is reading the change in current in milliamps of 12 volts to ground thru variable resistence. most sender housing are not grounded to the tank because of the gasket that seals their connection.

[zelatore]

Tidbart, you're correct that the black is actually the DC 'negative' instead of 'ground'. Lots of literature/manuals still use the term 'ground' though, right or not. I haven't checked the ABYC codes, but I didn't know green was used for anything other than bonding.

And you're also right about the possible confusion between the black AC hot wire and black DC 'ground' wires (not to be further confused with the green AC 'ground' wire). That's why ABYC has started using yellow for DC negative, though I've only seen it in heavy current situations like right at the battery neg post, engine blocks, thrusters, inverters, etc.

Heck, I've got half a spool of 4/0 yellow out in the garage now if anybody wants some...:kingme:

[mattyboy]

yes granted a boat that has ac and dc systems is a different animal for wiring , but i think badbird has a mid 70's 18 with just dc. working with negative and positive dc circuits all day I might over use the term "ground" but with out a "ground" to complete the circuit dc voltage will not flow. In most of the circuits I deal with the neg side is earth ground in a boat that would be block ground

[badbird]

Ok....so what I have left to do,is run a wire from the sender mounting screw to the DC main negative."This will be my grounding conductor ".

Thanks guys