Hi i recently fitted an oil pressure gauge to my classic Impreza, it's all wired up and fitted as recommended on instructions, but it doesn't work, do I need to ground the body of the sender unit? Or have I missed something

Any help would be appreciated.

Thanks in advance.

 

If the sender has 3 wires it shouldn't need to be earthed, but if it only has 2 then it probably will need earthing.

If it's a Pro-sport type gauge (3 wire sender) then the little plugs on the back of the gauge sometimes don't click into place properly so I would check that the sender wire is securely plugged in.

Obviously if the gauge doesn't even light up then it's a power wiring issue.

 

Thanks Tim, yes it's got three wires, ones ground second ignition and third to sender unit, everything lights up but the needle does not read correctly, the needles shoots up to 100 and stays there, I know the Gauge works as I tried it in another car which has a similar gauge and it read perfectly.

Thanks

 

OK - what gauge is it? Many/most gauges provide power for the sender rather than connecting it to battery - the sensors usually need +5V not +12V. But without knowing which unit you have it's difficult to advise.

 

The red and black wires powers up the lighting Of the gauge, the green goes to the sender unit and gauge, they are Dragon Gauges,

 

A quick search suggests the dragon sender only has 1 wire going to it so, yes, the body of the sender needs to be earthed. This is normally done through the 1/8" NPT threaded part being screwed in to the engine block, but if you have remote mounted the sender - via a braided hose perhaps - then chances are you will need to add an earth.
I will take a look.

 

Thanks mate appreciate that, so I just need to earth to body of sender unit?

 

Yes - give it a try

 

Will do mate, I'll update you soon as I've done it.

Atb

 

Earthed the sender to good ground, checked sender unit and wiring with tester and everything is fine power wise, but pressure Gauge still shoots to 100 when I the ignition is turned on and stays there, the other thing I've now noticed is that the temp gauge is fluctuating and wasn't doing that before.

Pressure Gauge works as i swapped the temp and pressure gauge wires around and it works.

Baffled as to what might be causing this not to work

 

Most likely is an installation error. Probably worth triple checking everything to the installation instructions.

I am not familiar with these gauges, but I did Google and found this thread on here so might be worth you looking at that and seeing if there are any clues?

Or you could have a duff sensor? If you disconnect the sensor at the gauge end does it read 0 or 100? If it reads 0, compared to 100 with it connected, then I would be suspicious of the sensor. If it also reads 100, then I would maybe suspect a break in the wire to the sensor.

Some basic electrical fault finding should find the issue.

 

Hi Tim thanks for the info,
If I disconnect the wire to the gauge the needle drops to zero, however if I disconnect from sender it stays at 100.

Regards

 

Check the whole length of the wire for breaks, abrasions, kinks that might hide a break etc.

Sounds like it's either short circuiting, or broken.

 

I've checked all the wiring all seems ok, emailed the guy who I bought the gauges from and he's sending me a new sender unit for me try, I'm hoping that should sort it,

Thanks for the advice.

 

If there is a difference in behaviour when you disconnect the wire at the sender, and the same wire at the gauge, it is most unlikely to be the sender at fault.

You need to check with a test meter that the wire is not shorted to +12V or to ground IMHO

 

New sender unit arrived today fitted it and still te same the needle shoots to 100 and stays there, Switch the engine off and needles falls to zero?

Checked all the wiring and everything seems ok, the oil temp and boost are running fine as the positive and negative terminals are all connected together,

This what I've done so far
Got a t piece conected to the car then added the the original oil pressure to the t piece then the gauge oil pressure sender unit was connected to t piece, the existing wire was connected to the original pressure unit, ran a wire from gauge sender unit to the gauge, hope that makes sense

Thanks

 

Could be a duff gauge then.

You are CERTAIN you haven't connected the gauge wiring to the old oil pressure switch?

 

Yes positive the old wire is conected to the original sender, then new wire from gauge sender unit goes straight to the gauge, the thing is I swapped the wires around temp/pressure, what happens then is the pressure gauge works fine but the temp gauge goes to 100 and says there,, I've rewired everything with new wires,

 

What make gauges are they?

Any connectors along the wires? Not possible they are reversed? What about at the gauges?

 

Hi
They're Dragon Gauges, only connecters are male/female spade conectors,
There's 3 wires that come from directly behind the gauge red black and green,

 

So what do you have the red/black/green connected to?

 

Thanks mate got it sorted finally,
Red to ignition, black to Ground, there was a fine slit/cut in the wiring which was touching the body of the vehicle hence Gauge not working.

Thanks for everyone's help appreciate it.

 

LOL, thought you had put all new wiring in place?

 

Well I thought it sorted itself out, after unistalling it and reinstalling it, now it's reading backwards,