Temp gauge reading high XU5JA

[309SRiguy 15]

The temperature gauge is flicking straight to high when I turn on the ignition. The XU5JA is in a 309 but the engine is the same as the 205 GTi of the same era. I replaced the sensor about 1000miles ago when the old one started to read higher than usual, working OK but in the wrong range.

I tested the 2pin blue top sensor. 2700 ohms across the pins. I had 11v from the supply wire (orange) so tested from the ECU plug to the sensor and found 50ohms resistance. The green wire which goes to earth would not show any contact with earth at all.

I took the leap and spliced a new wire for each and earthed the green to the earth mount by the coil. Both new circuits showed a nice fault free result. The original wires were cut and the new wires fitted to the old  ends so I could use the ECU and sensor blade connections.

After replacing everything and turning on the ignition it was disappointing to find the needle flicking straight to the top.

I have no voltage at the sensor now. There is no fuse in the circuit as for as I can see.

Does anyone have a suggestion about what is going on? Is the ECU now failing to provide any power to tab #10 the orange wire?

 

The car was running OK. I think the mixture was slightly richer because the light pinking on a light throttle seemed to have gone. It is not running hot and is pulling cleanly.

I have to make a fairly long trip. What are the likely results if I run the car with this fault?  How much does the LE2 Jetronic alter the fuel ratio based on the feedback from this sensor? Is it enough to cause sluicing of the bore leading to damage or will it just use a bit more fuel? ( The SAD handles cold starts and leans out as it heats so all is OK there)

I really have to make the 200 mile trip and I am in a remote location with no alternative transport. Should I attempt it?

 

M889 is the sensor orange is 'or' and green/yellow is 'vj'

 

 

[Tom Fenton 1,542]

That 2 pin sensor has no relation to what the gauge on the dash shows. If the gauge is going straight to the top, you have an earth fault most likely on the single wire that goes to the sensor for the gauge.

[SRDT 175]

Look at 43/118 on your PDF for the temp gauge wiring. There is also a water temp warning light (at 47/118) so if you really have a problem it will show on the dash even with the gauge not working.