Wayward temp gauge

[Ronaro]

So after around ten days of sitting unused I took the Ro for a little drive. All was well until after around half an hour when I noticed a usually rock steady temp gauge fluctuating between quarter and it’s normal position. Having stopped and checked both the coolant and oil levels (both are spot on and no leaks) it then went back to its normal position. Since then it struggles to go above the quarter mark but then when I look again it is on its usual mark. The photo is where it usually is.
Could this be the thermostat or a dicky sensor - or something else?

[Lincsls1]

It could well simply be the sender. I once had an old Rover car that had a temp gauge suddenly start going waffy, everything else about the car was fine. It was just the thermistor sensor that solely drove the gauge. There was another sensor that controlled the fans.
If its simple enough to change I'd start there first.

[Ronaro]

Thanks for the reply. This is pretty much where it hovers before going back to normal.

[THUNDER STORM]

I would be tempted to try sensor and no difference change thermostat

Ade

[Ronaro]

Agreed. Is it easy to get to as I’m not entirely sure where on the LS1 it is located?!

[mfp4073]

Ronaro said:

Agreed. Is it easy to get to as I’m not entirely sure where on the LS1 it is located?!

Its on the passenger side cylinder head at the front of the engine, next to the exhaust manifold, very easy to get to.

[Ronaro]

Thanks mfp

[S0updr4g0n]

Had a similar issue, LS2 though..

It would reach temp ok but then on close inspection (idling on driveway) it would fluctuate between temperatures (+-15 degrees) from readout. I missed it initially as the drop on a run seemed like the stat was opening and there was enough airflow to compensate. In reality, the coolant sensor was bad, fans never kicked in for long when in traffic (needle didn't rise either) and thus the temp went up and the oil temp rose unacceptably.

Coolant sensor gets my vote here, if the stat and oil pressure sensors are of a similar age, I'd do them too but coolant first. YMMV.

[stevieturbo]

Get a proper scan reading of the temperature,. OEM dash gauges rarely reflect an accurate temperature

[Ronaro]

mfp is this the sensor in the centre of the photo?

[mfp4073]

Ronaro said:

mfp is this the sensor in the centre of the photo?

Yes that's the one, if I rember correctly there are three pins in that connection, one for the temp gauge and two for the PCM which controls it all.

[Ronaro]

I meant to update this ages ago, but after a couple of good runs it righted itself and now stays firm at its correct position. I guess it didn’t like me going away for a bit

[ianwayne]

mfp4073 said:

Yes that's the one, if I rember correctly there are three pins in that connection, one for the temp gauge and two for the PCM which controls it all.

Mine only has two (2004 LS1), supplying the gauge only, and coincidentally I'm after one, having discovered today that mine is only held together with a bit of glue!

Searching provides the OEM part number as 12608814. There are lots of alternatives though, it seems to be used by a vast number of car manufacturers.