Sigma Gauges

[chelrob]

I have a 2011 Sigma and both Fuel Gauge and Oil Pressure gauge are reading zero. I started out by checking the actual fuel gauge by shorting the sense terminal to earth - the gauge reads full so that seems ok…

I was then about to set to work checking things at the sender end – but thought I would search on here first. Seems on older cars the sender signal is a black & green wire that goes straight through to the gauge. However, in my case it is a yellow at the gauge end (although there is a green/black at the tank). Looking at the wiring diagram, the yellow at the gauge comes from the tacho! Anyone know what is happening here – does the sender signal just get wired into tacho and then straight out again, or is the tacho actually doing anything?

Anyway using a multimeter to check the various lines, gives the following:

Yellow from gauge to Tacho - Good

Green/black from Sender to Tacho – Good

Sender: green and black terminal to earth terminal is reading ~28Ω (tank ~quarter full)

Tacho: green and back terminal to yellow terminal open circuit

If the signal is supposed to go straight into the tacho then straight out, the above would suggest a tacho fault? But what could possibly go wrong with a direct internal connection??

Same question goes for the oil pressure gauge – I see that this is also fed from the tacho…. Seems a coincidence that both gauges fed from the tacho have failed? Could this be a similar tacho fault (though it’s working fine as a tacho)?

Any thoughts /experience would be welcome… Thanks

[Jonathan Kay]

Which terminal on the tachometer are these connected to/ What are all of the other connections on the tachometer with their wire colours? 

Ordinary instruments, not Stack?

Jonathan

PS: I'll go and find the diagram, but as a first approach if more than one instrument fails at once suspect what they have in common: the power feed/fuse and the earth. But you might be beyond that already...

 

[chelrob]

Jonathan - Yes ordinary instruments. Have checked power and earth for the fuel gauge and definitely ok. Not got as far as the oil pressure yet. Earth to the tacho must be ok as it is working ok as a tacho...

[Jonathan Kay]

Edited: Crossed with yours... please ignore.

Jonathan

 

[chelrob]

Connections to the Tacho match the wiring diagram exactly. Yellow is 3rd from the end and green/black 6th.

    Just tried bypassing the Tacho and connecting the black/green feed from the sender, to the yellow from the guage and now get a reading (albeit higher than I was expecting, tho maybe there is more fuel than I thought)

     Seems strange that this connection is open circuit within the Tacho...Not something that I would have thought an obvious failure or am I missing something here?

   Anyway the question is do I fork out £175 for a new tacho or stick with my bit of wire?? Then we also have the same issue re. the pressure gauge to resolve...

[Jonathan Kay]

How's it going?

Have you worked out where the Yellow wire connects to the Green/Black?

Jonathan

[chelrob]

Not had chance to spend any more time yet, but they just seem to connect together within the Tacho. Would be tempted just to short across and bypass the Tacho, but I seem to have a similar problem with the oil pressure. I haven't worked out the wiring for that yet as the diagram that I have just seems to show a pressure switch and not a transducer.... more head scratching..

[roachw]

On a related topic, my sigma gauges keep splitting!

oil pressure first and now temp. The car is only 18 months old, anyone else had this problem I wonder?

 

 

 

[Jonathan Kay]

Where are they splitting? (I don't think I've heard of this before.)

At 18 months I'd ask for replacement by the vendor.

But they can probably be repaired.

Jonathan

[roachw]

They split around the front edge, so just behind the black plastic bead/rim. It's actually the white plastic body that splits away. Oh and the posts have broken off too. I'll try to post a picture of it.

regards,

Will

[roachw]

[roachw]

this is the "repaired" item..