guages all messed up..please help fix

[imraan47]

Hey guys.
Ok so i went to replace the dash pannel which is going great. I wanted to see how the wiring all is to re-wire the lights which i got alot of help on previous thread. Now i look at all the wire's for the guages and they are all mixed up and the guages arent even all at zero.
how do you reset them back??? i guess it has to do with grounding them properly right?
here are the pics...i cant find any where how to really hook them up all the way to the harness, which there are two (black and white)

1988 glasstream tempest 120hp mercruiser

Tach and Oil guage:

Temp guage:

Fuel:

 

[imraan47]

Re: guages all messed up..please help fix

Ignition:

Batt and speedO:

Fuel & battery:

The MESS!

 

[underwurlde]

Re: guages all messed up..please help fix

Hello again.

Now that's what one calls a 'rats nest'. Looks complicated but actually it's quite simple - many of the connections are repeated (e.g. common grounds, power, back-lighting).

The way the original wiring is done seems OK to me... it doesn't look 'bad', it looks a mess in your picture because it's all there, loose items connected up, but there are looms (bundles of wires taped up) and this is good, some thought has gone into the orignal wiring and it has not been done on an ad-hoc point-to-point basis (which would be a right bl00dy mess).

At the mo, I therefore don't think anything is inherently wrong due to 'bad earths' (although I am not dismissing that idea)....

....and the guages arent even all at zero.
how do you reset them back??? i guess it has to do with grounding them properly right?

So let me guess. Even with the power to all those guages completely OFF, the guages are still not zero'd correctly?

Cheers,

Andy

 

[Don S]

Re: guages all messed up..please help fix

From the OEM service manual.
Plus, there is a whole section on instruments.
Mercruiser Service Manual #10

 

[imraan47]

Re: guages all messed up..please help fix

Yes underwurld, there is no power to them at all (battery pos and neg are both unpluged and yet not all show zero!

I have the seloc manual for 1992- which i assume is the same concent interms of the wiriing. what is confusing me is how to follow the wires and know whats is happening at the harness and from the harness where are they actually going? also why are there 2 harness (black and white). When i look at this it seems like the guages on the right and left are split interms of wiring then they hook up at the harness somehow

 

[Fl_Richard]

Re: guages all messed up..please help fix

Zero usually does not register until they have power.

 

[imraan47]

Re: guages all messed up..please help fix

Zero usually does not register until they have power.

ok so i wont be too worried about that right now...just all the other stuff

 

[underwurlde]

Re: guages all messed up..please help fix

Yes underwurld, there is no power to them at all (battery pos and neg are both unpluged and yet not all show zero!

The guages may be of the moving coil type. The indicator needles within each guage are moved by a solenoid acting against a magnet. The needles are held 'at zero' by a spring, hence the more juice through the solenoid, the futher the needle moves around the dial. All very mechanical in other words - to keep them cheap the offset zero position can be altered by adjusting the spring and this can be done via turning a screw either at the back of the guage or sometimes at the front.

The majority of the signals that drive the guages come from the engine, sometimes via the throttle control box. These will be some or all of the connections shown in DonS' post. This may be one of your looms.

Other signals come from 'around' the boat such as your fuel guage and speed (which will be hydraulic). This may be the other of your looms.

Guessing here, but each guage may have something like:
1) Connection to Batt- (guage power) - connect to Batt-
2) Connection to Batt+ (guage power) - connect to IGN (some guages such as your moving coil guages may not need this)
3) Connection to Batt - (guage backlight power) - connect to 1)
4) Conncection to Running Lights (guage backlight power) - connect to running lights
5) The signal wire. Connect to signal source.

The voltmeter won't need 5) as the 'signal' will be the number 2) connection.

Does that make sense? (pardon the pun).

Andy

 

[imraan47]

Re: guages all messed up..please help fix

Guessing here, but each guage may have something like:
1) Connection to Batt- (guage power) - connect to Batt-
2) Connection to Batt+ (guage power) - connect to IGN (some guages such as your moving coil guages may not need this)
3) Connection to Batt - (guage backlight power) - connect to 1)
4) Conncection to Running Lights (guage backlight power) - connect to running lights
5) The signal wire. Connect to signal source.

The voltmeter won't need 5) as the 'signal' will be the number 2) connection.

Does that make sense? (pardon the pun).

Andy

No sense of this at all!

 

[underwurlde]

Re: guages all messed up..please help fix

OK, sorry about that then, didn't mean to confuse you.

Andy

 

[Fl_Richard]

Re: guages all messed up..please help fix

Purple wires are +12VDC when the key is on and supplies power to the guages. These can be looped from guage to guage or one wire from each gauge all connecting to the purple in the harness. All gauges will get a purple wire.

Black wires are all grounds and can be all hooked together then to the black on the harness. These can be looped from guage to guage or one wire from each gauge all connected to the black wire in the harness. All gauges will get a black wire.

Lt Blue is from the oil pressure sender and attaches to the S on the oil gauge.

Tan comes from the water temperature sender and connects to S on the water temp gauge.

Grey comes from the engine and connects to the S on the tachometer.

Brown-White comes from the oil temperature sender and attaches to S on the oil temp gauge.

Its really pretty simple, each gauge gets power (purple) a ground (black) and the sender(Tan, Brown/White or Lt. Blue) wire from whatever the gauge displays. How the purple and black wires get to the gauge doesnt matter for operation but they are usually looped from gauge to gauge.

As for the white and black harnesses... do you have twins? Perhaps one comes from each?

Whatever you do buy the right colored wires (if you need additional length). If they are all black and you have a problem you'll never find whats wrong.

Hope this helps!

Richard

 

[imraan47]

Re: guages all messed up..please help fix

As for the white and black harnesses... do you have twins? Perhaps one comes from each?

What do you mean by twins? to me as i traced the wire it looked as if they are connected as primary and secondary then they go to the back.

You mentioned about the ltblue wire...well that is hanging out since last season and i need to trace it. i see that all of the sudden the ltblue wire goes into becoming yellow with a red strip then goes into harness. this confused the heck out of me!

 

[Fl_Richard]

Re: guages all messed up..please help fix

Twins - Dual engines.


I think Yellow-Red is choke.

 

[imraan47]

Re: guages all messed up..please help fix

Twins - Dual engines.


I think Yellow-Red is choke.

oh in that case..no it isnt a dual engine. the boat isnt even made for a dual engine.

i dont have a choke system on the engine or anywhere. its just a merc 2.5L engine 120hp 1988

 

[Fl_Richard]

Re: guages all messed up..please help fix

Other than coming over drinking your beer and fixing it myself I think I'm out of help....

Sorry

Richard

 

[imraan47]

Re: guages all messed up..please help fix

Your most welcome to come down but you are really far.
I will try and tackle it based on what you have said above. Today weather was horrible here...we got trees going down and stuff with 70-100km/hr winds.
anyhow i will post back when i get to the boat again.

 

[imraan47]

Re: guages all messed up..please help fix

ok finally got to the boat and tried to figure it out...
damn sucker dash pannel i made is a little too big so i need to trim the edges.
i tried to follow the wires and back the the engine. its not exactly as the diagram above or from the 1992+ seloc manual..i found one in my ref library that covers the 1988 engine but cant check it out so i will have to go in this week and photocopy the pages there and compare.
my issues are the wires aren't even looping up to make any sence to me because of the other 2 white harness...oh ya btw there are 2 of thoes!

another problem i didnt notice on the diagrams i have from manuals is that the speedmeter is not shown?? so how exactly is that hooked up if anyone can point this out to me please.

i did my best to trace the purple, black and red wires the way Fl Richard said and also based on diagram. then i plugged the terminals to batt and the guages still dont set to zero. i turned ignition on and still nothing changes.
i couldnt fire the engine yet because it still needs to be summarized but i need to deal with all these wires otherwise it could short out with sparks LOL.

 

[seabob4]

Re: guages all messed up..please help fix

imraan,
All the speedo needs is the blue and black for back-lighting. The speedo hose is water pressure, no electrical needs at all...

 

[imraan47]

Re: guages all messed up..please help fix

imraan,
All the speedo needs is the blue and black for back-lighting. The speedo hose is water pressure, no electrical needs at all...

ok kool so thats what i have done. the blue just pulled from gauge to gauge and likewise with black as ground
i will be going to the boat on saturday so dash will be in place along with the gauges. i wont be able to test them since engine still needs to be fired up for the first time for this season to begin

 

[imraan47]

Re: guages all messed up..please help fix

Hi guys.
ok i got the dash in and looks good..all guages in and put the ignition on and every guage reset to zero EXCEPT fuel guage!!
So WTF is going on here..it pretty much stuck at just less then 1/4 so it reads as 1/4tank gas. it read that since i took everything apart. Originally before i took the dash out the fuel guage was working and i put the wires back where they went. i dont think that i have mixed anything up. can someone help with this issue.
also the damn backlights for all guages DONT work!!! i dont know what is wrong. is there a way to temporary hook each one maybe by passing a small wire and see if each lights up so that way i know that the should be working??? i was thinking of just using a small black wire, 14guage and hook that up to the neg bus and shouldn't it light up just fine???