Recently the engine temperature gauge on my Laguna (2 litre petrol 
engine) has started reading low - hardly moves off the bottom of the 
gauge unless I let it sit idling on the drive for several minutes. 
The gauge is dual function and shows engine oil level when the ignition 
is first switched on and that works fine so the gauge itself is OK.
 
I'm pretty sure that the actual engine temperature is OK too and that the 
thermostat isn't stuck open because the bottom radiator hose stays cold 
until the engine has been running for a while and then gets warm as the 
thermostat starts to open. Heater temperature also seems about right. 

The sender unit is fitted into the thermostat housing and is simply held 
in place by a clip - not a screw in type.  This suggests to me that it 
isn't going into the actual water system so can be simply pulled out and 
replaced but the Haynes manual isn't very helpful in this area. I've got 
a new one from the Renault dealer but the resistance when cold measures 
very close to the one on the car so I'm not convinced that the existing 
sender is actually duff. It may well be a problem with the regulated 
voltage that feeds the gauge/sender, the circuitry of which is gonna be 
hidden up behind the dashboard somewhere - something I don't fancy 
fighting my way into.
Has anyone else changed a Laguna temperature gauge sender and if so, can 
it be simply pulled out of the recess it sits in without having to 
partially drain the cooling system?
Also, could anyone tell me what voltage is fed down to the sender so I 
can check on my Laguna to see if it's low.

-- 
Roger Shilcock

The VW senders are similar, but they do contact with the coolant. If the 
resevoir cap is on and the engine is cool, you should be able to pull the 
old one out and replace it without losing too much coolant. Sensor voltage 
is usually 4.5 - 5.5 volts.



"Roger Shilcock"  wrote in message 
news:Xns96CBA08D56AA1shilcorukibmcom@32.97.166.131...

> Recently the engine temperature gauge on my Laguna (2 litre petrol
> engine) has started reading low - hardly moves off the bottom of the
> gauge unless I let it sit idling on the drive for several minutes.
> The gauge is dual function and shows engine oil level when the ignition
> is first switched on and that works fine so the gauge itself is OK.
>
> I'm pretty sure that the actual engine temperature is OK too and that the
> thermostat isn't stuck open because the bottom radiator hose stays cold
> until the engine has been running for a while and then gets warm as the
> thermostat starts to open. Heater temperature also seems about right.
>
> The sender unit is fitted into the thermostat housing and is simply held
> in place by a clip - not a screw in type.  This suggests to me that it
> isn't going into the actual water system so can be simply pulled out and
> replaced but the Haynes manual isn't very helpful in this area. I've got
> a new one from the Renault dealer but the resistance when cold measures
> very close to the one on the car so I'm not convinced that the existing
> sender is actually duff. It may well be a problem with the regulated
> voltage that feeds the gauge/sender, the circuitry of which is gonna be
> hidden up behind the dashboard somewhere - something I don't fancy
> fighting my way into.
> Has anyone else changed a Laguna temperature gauge sender and if so, can
> it be simply pulled out of the recess it sits in without having to
> partially drain the cooling system?
> Also, could anyone tell me what voltage is fed down to the sender so I
> can check on my Laguna to see if it's low.
>
> -- 
> Roger Shilcock
> 

On Thu, 08 Sep 2005 20:53:28 +0100, John wrote:


> The VW senders are similar, but they do contact with the coolant. If the 
> resevoir cap is on and the engine is cool, you should be able to pull the 
> old one out and replace it without losing too much coolant. Sensor voltage 
> is usually 4.5 - 5.5 volts.




The clips to get them out are a complete and utter arse if they are like
my Laguna.  You need two very small screwdrivers and have to push both
sides in and pull the sender out at the same time.  Have you got three
hands?