Coolant temp sensor

Hi

After replacing the battery on my Alpine GTA turbo I fired the car up and let it warm through

The coolant temperature gauge did not work. Gauge moves to the 50 degree spot with the ignition is put in but moves nowhere there after. The fans still kicked in when warm so I assume it's either the sensor in the engine or a fuse possibly ( I've checked all the fuses but can't see any blown ) ? Also the front fans came on but the blower in the engine bay did not seem to trigger when the engine was switched off ?

Any suggestions ? Also I assume the sensor for the gauge is located around the thermostat housing somewhere but I can't locate it or see it mentioned in my workshop manual?

Thanks
Brad

Sensor is on the rhs of waterpump .Only feeds gauge,has no other function.
Rad fans are triggered by sensor in the rad and bay fans are switched by sensor on bracket near turbo .None are related .
Sounds like the sensor has packed up .It shouldn't move to 50 with ign,it should only wiggle a bit to base point .Readily available on Ebay .

http://www.ebay.co.uk/itm/Renault-25-2- ... SwawpXsB--

Thanks Lee

Yes the needle just wiggles a little onto the 50 mark and then does not move any further up so looks like the guage is working.


Are there any pics showing location ? I can't see any diagrams showing it in workshop manual? Does anyone have the part number for a new sensor so I'm sure I get the right one ;0)

Also if it's a bit further down near the pump I assume I will lose a fair bit of coolant when changing ? Is it best to drain down first and then change or let the coolant drain out when changing. I changed all the coolant last year and flushed through and replaced with correct coolant.

Cheers
Brad

Sorry just seen eBay link so ignore my part request ;0)

It might be worth just unplugging the lead from the sensor, and see if you get a different reading when switching on the ign.

It does not really read to honest . Just moves up a fraction on ignition turn on and then does not shift.

Give the plug/wires a wiggle when it's warmed up a tad .See if it moves.

Bought a new sensor as they were only a fiver so going to replace it anyway.

Has anybody got any pics / diagrams on location and replacement advise ?

Will i lose much coolant when replacing ?

Cheers
Brad

Yes you will lose a bit,not much,no way round it unless you drain it a tad before removal .I wouldn't bother overly but just put a washing up bowl underneath and catch what you can

Here....RHS of the pump,plug fits to sensor .Other side is for ECU and has flying lead.

WP_20150822_001.jpg

Thanks Lee. All much clearer now . Much appreciated mate .

Brad

Will i lose much coolant when replacing ?

Brad ...... the trick here is with the engine cold, undo the coolant reservoir cap to release the pressure, then do up again. With the thermostat closed and no pressure in the system, and very little head of coolant ...... If you slacken off the old sensor till it is loose enough to turn with your fingers of your left hand .... have the new one ready in your right hand .... unscrew the old one and quickly pop in the new one and give it a couple of turns. If you are quick, I would be surprised if you lost any more than a tea spoon full of coolant.

So I have just tested the new sensor before fitting it to the car to ensure that it was the sensor.

So to test it I connected the plug from the loom to the new sensor , switched on the ignition and then placed the sensor in some boiling water. Temp Gauge still did not rise? Does the sensor need an earth possibly of being screwed in to operate? I am pretty sure its not the gauge as this flicks up slightly when I turn on the ignition so its still alive it seems. Could be a broken wire somewhere I assume?

This stopped working after I changed the battery the other week so I am not sure if is related?

Are there any other tests I can perform with a multimeter to start ruling things out?

Thanks
Brad

Does the sensor need an earth possibly of being screwed in to operate?

The answer to your question is Yes. ....... There are two wires coming from the sensor and both will not operate unless the sensor is grounded by screwing it into the thermostat body. One of the wires goes to operate the gauge, and the other goes to operate the over temperature warning light on the RHS of the instrument unit. Both require the earth return to work.
Of course the thing is that the OE temperature sensor does both the gauge and the warning light, but do other non OE temperature sensors incorporate the warning light switch........ that I do not know.

Thanks John

I will earth the sensor and test it again tomorrow ;0)

Thanks again

Brad