No water temperature reading

[boxerairhead]

I've recently bought a T25 with an EJ20 engine in it. It all works and drives fine except the water temperature gauge doesn't work.
So far i've done the following.

1. Bought a new sensor, unplugged the old one and plugged the new one in and dropped it in a mug of hot water, no reading.
   
2. Earthed terminal 6 on the loom plug to the body and the gauge slowly crept to max,
   
3. Put 12v across the 2 outer terminals on the back of the gauge and it crept up to max
   

From this can i assume that the gauge works but the wiring from the sensor to the front is faulty?
Can i just run 2 wires from the plug underneath and to the gauge in the cluster bypassing the loom?
The other thing to note is if the plug is not on the sensor the car will not start, seems strange too.
Any ideas of what else to check/look for please?

[silverbullet]

Does the engine conversion have any provenance i.e.is it an RJES harness or some diy hack job or worse (old TSR)
afaik the Subaru gauge temp sender has a different resistance value range compared to the VW one, so the wiring needs a resistor mod to make the gauge read about right.
One of the Fuji Heavy lot will be along eventually with more info.l, or you go to fb and find the VWKD Subaru group which is the RJES information source.

[boxerairhead]

Thanks for the reply. I've sorted it now i think. The dealership sold me the ECU sensor not the gauge sender so i just assumed that i was tracing a fast of that system and it wasn't until i un plugged it and tried to crank it over that it dawned on me that something wasn't right.
I had a new sender in the garage drawer, as you do, for something else so rigged up a little tester with a cup of boiling water and the gauge worked straight away so from that i take it the sender is u/s and i've ordered a new one.
Conversion wise, i have no clue who did it but its not a diy job as far too neat and tidy but no bills or invoices for the work done as lost by previous owner.
Hopefully now this will solve the problem and i'll go and check out the FB drop you recommended. I've been in contact with Richard from RJES who was a great help with something else.

[slowcoach]

Is it a 3pin or 2 pin temp sender? The 3 pin has the gauge sender, ECU signal, and earth al together. If it's a 2 pin one, then you'll have 2 separate senders, one for ECU and one for the gauge. Both are under the intake manifold but easy to access as far as I know

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