Water Temperature gauge

[fastlady]

OK I know I'm going to get flak for being female and posting these sorts of dumb technical questions.... but if ya don't ask ya don't learn, so here goes anyway! 😬

 

Just bought a Seven last month (1.8K Roadsport) and it has a dual oil / water temperature gauge with a switch in the dash to toggle between them. I noticed the other day that when switched to water temperature the needle was at the left hand side of the scale permanently, no matter how long I'd been driving. It had been working OK a few weeks ago when I first bought the car & the oil temp. reading (apollo tank) is fine and sits at around vertical, reading around 60-80 on the gauge, when the car has warmed up, which is I guess what I'd expect for a 'normal' reading.

 

I did a bit of a search on the Tech Talk forum and came up with some suggestions to test the temperature sender by shorting out the wiring from the sender to the gauge with the ignition on.

 

So here's the stoopid question - what exactly IS a sender and where can I find it on the car to do the test on the gauge??

 

Also I did find at one point that fiddling randomly with the wires at the back of the gauge seemed to bring back the reading temporarily. So I'm not sure if this is actually just a faulty connection to the gauge or whether that was just coincidence and it really is a problem with the sender - so if anyone can point me at a diagram or explanation of what the wiring at the back of the gauge should look like so I know exactly which connection to check that would also be really helpful.

 

TIA,

FastLady

[JAG]

THE BAD NEWS; Can't direct you to where the sender is or what wiring on the back of the gauge should look like - I don't own a Caterham 😳

 

THE GOOD NEWS; A sender is 'normal' speak for a temperature sensor. It sits somewhere on the engine immersed in the engine coolant. It tells the gauge how hot the coolant is getting by changing resistance in proportion to the coolant temperature.

 

Take no notice of the uppity 'types' on here - THE ONLY STUPID QUESTION IS THE ONE YOU NEVER ASKED

 

 

Justin

 

A closed mouth gathers no foot.

[Shaun_E]

Water temp sender is in the water rail but I can't remember which end. Follow the radiator top hose to where it joins a black metal pipe mounted on the engine - this is the water rail - and you should easily find the temp sender near one end of it. Not sure that shorting it will cause a reading as I would have thought that as the temp increase then so does the resistance - shorting will effectively give you zero resistance and therefore a low temp reading.

If fiddling with the wires has an effect than it could be the connections from the sender to the switch that flicks between water and oil temp are what is causing the problem. Probably just need cleaning up or maybe the connectors need re-crimping to the wires.

 

Yellow SL #32

[James Tricker]

pic here

(just to the left of where the chain is shackled to the engine)

 

James (1.8 SV)

[Ozzy]

Top Tip!!!!!!

 

Join your local Caterham owners club. Always loads of very nice people, willing to help novices (like me).

 

Still Shaking

[paulyb]

Agreed with Shaun...sounds most likely to be a connection with the switch.

 

I'm in Kensington if you want to bring it over to have a look

[pinstripe pete]

The temperature sender can be found on the water rail where it exits the engine block (ie passenger's side). See James Trickers post above. There are two fittings in the water rail here; the temp sender is the one closest to the block and it only has one wire coming out of it (as opposed to the other one which has two; not sure what this one does). Temp senders are always playing up and sending worrying messages about the coolant temperature (most recently for me on the Isle of Skye miles and miles from civilisation; 120 degrees indicated - nothing wrong with the engine).

 

CC do a replacement; they're very cheap and easy to fit in. However, it's a tapered thread so don't overtighten it; ISTR that it only needs to be tightened until it just grips.

 

I've had my VVC for just over one year and will soon be on my third temperature sender!

 

'A gentleman is a man who opens the door for his wife to carry the coal in'

[Trevor Newman]

If you pull the green /blue wire off the sensor at the rear of the engine and short the insultaed metal tab to earth (ie something metal on the car or engine) it should give you Max temp on the gauge

if not get your compact mirror to look behind the dash

and see if you have 3 wires on the back of the switch the water temp wire should be green with a blue stripe

if you need a sensor it will be cheaper from your local motor factors

[j_thombs]

Definately sounds like a temp sender failure to me. It is located as described/shown above and is the small brass threaded part. The other part next to it with the brown or black connector is the temp sender for the ECU which thankfully is about 1,000,000 times as reliable as it is actually used for something important. You can check the gauge operation (again as mentioned) by removing the connector (green wire I think) and touching it against the engine block, the gauge should show max temp.

 

The temperature sensors are about £8 from Caterham and are not difficult to change so long as you don't overtighten them.........

 

Jon

 

Ex Beaulieu no31 and now ex Supersport R......so 7less at the moment

 

My Caterham Pics

[Chris W]

For the avoidance of doubt, please note that to do the test above, the ignition needs to be ON.

 

I agree it's most likely to be the sender although they normally fail a bit erratically at first rather than completely failing. It can't be the gauge if the gauge is OK on oil.

 

Before you replace the sender, it would also be worth checking that the connections on the back of the toggle switch (ie: the water/oil gauge switch)are all sound. It might be that one of the wires (the water sender side) has come adrift. If all looks well on the switch then replace the sender.

 

Chris

 

2003 1.8K SV 140hp see it here