Temperature guage reading

[stuarte]

Hi all,

According to the temperature guage in my 400, the fans have always kicked in at just over 90 degrees. However, the last couple of days the fans have started kicking in at at about an indicated 78 degrees and the guage never goes above this.

Since I'm a spanner with a spanner, any advice as to what might cause this? Where do I start?

Cheers.

BTW, i've tried using the woeful PH search facility but to no avail...

[portzi]

hi Stuart, simple things first, try the connector to the temp sensor, sometimes they can get dirty or work itself loose, someone here will put a photo up to its whereabouts , but its right behind the Dizzy, just remove the cap to gain better access to remove the connector, give that a go first.

Mark

[stuarte]

Thanks Mark. I'll take a look. Pretty sure I know where the sensor is now (thanks to the power of google). Cheers, Stu

[JPW231]

Similar query I guess?
My temperature gauge has been rock steady and the fan kicked in at around 90C for the couple of months tat I've owned te car..
Recently it's started to flicker between 60-70C (and I mean flick between the too, rarely remains steady as it I'd), although if I leave it after a run the fan kicks in, although it doesn't seem to get anywhere near 90C.

Any ideas? Just checked the sensor connection, although its bloody hot! Should've learnt - I changed the temperature sensor on my Golf today & got a shock as the coolant was far hotter than I was expecting :-(

[ChimpofDarkness]

You all need to do the Range Rover sender mod.

[JPW231]

Which is?????

Just a new sender?

[ChimpofDarkness]

JPW231 said:

Which is?????

Just a new sender?

Nope, you've already got a Range Rover sender stuck in the inlet manifold, TVR just never used it.

Pull the wire off the TVR sender & connect it to the Range Rover sender.

You'll need a variable resistor from Maplin too.

Adjust your variable resistor to tune the TVR gauge with the Range Rover sender and it's job done.

You can use the fans cutting in at 85+ ish as a general guide to tune the gauge.

You will find the temperature rises faster on warm up and the readings are more consistent on the gauge.

http://lmgtfy.com/?q=Range+Rover+sender+mod

[JPW231]

Thanks. Not sure why it was rock steady and the fans cut in at the right time since I've had it and now it wavers?

[Dr Mike Oxgreen]

On that thread you mentioned buying a thermistor. Why was that necessary - is there nothing behind the Range Rover sender?

[ChimpofDarkness]

Dr Mike Oxgreen said:

On that thread you mentioned buying a thermistor. Why was that necessary - is there nothing behind the Range Rover sender?

A temperature sender is a thermistor.

Any electrical device designed to show a change of resistance in response to temperature change can be refereed to as a thermistor.

A temperature "sender" is how how some might typically refer to the thermistor that controls the resistance seen by the temperature gauge (IE: sends to the gauge).

A temperature "sensor" is how some might typically refer to the thermistor that controls the resistance seen by the ECU (IE: sensed by the ECU).

The truth is they are all one & the same thing, a thermistor.

[stuarte]

Thanks CoD. I think I'll give that a go when I can find someone that knows what a sender is and what a variable resistor is and what a Range Rover is.

No, looks pretty straight forward even for a retard like me.

Curious though, exactly like JPW, my gauge read just over 90 when the fans cut in for exactly the first 2 months of owner ship. Now reading late 70s. Spooky...

[Dr Mike Oxgreen]

CoD: I know what a thermistor is. I was using the words "thermistor" and "sender" interchangeably as well.

Your post earlier in this thread implies that all you have to do is disconnect from the TVR sender and connect to the Range Rover one (with a resistor for calibration purposes), but your post on that other thread talks about needing to buy the thermistor. That's where my confusion lies.

Is there a thermistor lurking under the Range Rover sender, or is it empty and hence you need to buy the thermistor to populate it?

Edited by Dr Mike Oxgreen on Saturday 4th August 18:08

[slideways]

ChimpofDarkness said:

JPW231 said:

Which is?????

Just a new sender?

Nope, you've already got a Range Rover sender stuck in the inlet manifold, TVR just never used it.

Pull the wire off the TVR sender & connect it to the Range Rover sender.

You'll need a variable resistor from Maplin too.

Adjust your variable resistor to tune the TVR gauge with the Range Rover sender and it's job done.

You can use the fans cutting in at 85+ ish as a general guide to tune the gauge.

You will find the temperature rises faster on warm up and the readings are more consistent on the gauge.

http://lmgtfy.com/?q=Range+Rover+sender+mod

Don't spose you have the variable resistor part number?

[Alexdaredevilz]

Pm Nigel he has my resistors

[ChimpofDarkness]

slideways said:

Don't spose you have the variable resistor part number?

Honestly you lot

All you've got to do is invest 3 minutes to read the post I linked you to

http://web5.pistonheads.com/gassing/topic.asp?h=0&...

Read it fully & you will see that I bought a 0-1000 Ohm variable resistor from Maplin for £1.62.

You will also see I measured the resistance of it once it was tuned to the gauge.

I then said this:

"In both tests the variable resistor value required to exactly match the gauge scale was 170 ohms"

And this.

"The variable resistor will stay put until I get myself down to Maplins for a fixed rated 170 ohm resistor"

Alex came up with this years ago, I just followed his lead & tested it on my car.

Today I did some more testing while running my Canems ECU software that shows the true coolant temperature.

My Range Rover sender mod is confirmed to follow the original ECU coolant temp sensor used by the Canems system.

Well it follows it perfectly from cold start right up to 85* and is therefore a significant improvement on the original TVR sender.

However, from 85* the Range Rover sender mod stalls out hovering at a steady 85*, while the Canems software shows the true coolant temp at idle actually rises to a maximum of 98*.

I've tuned the fans using the Canems software to maintain an average true idle coolant temperature of 95*, doing so it never rises above 98* and never falls below 92* at hot idle.

At a true 98* my TVR gauge woth the Range Rover sender mod never rises above 88*, basically it's about 10* behind but only from 85* on if that makes sense?

My TVR gauge will still show a dangeouse increase in coolant temperature because I tested it my taking the fan fuse out.

Like this I watched the true temperature rise to 105* the TVR gauge followed showing 95* at which point I aborted the test on the grounds of safety.

So if I ever see the TVR gauge rise to 95* I know it's time to pull over and make some checks.

Finally I did some hot running tests, the Canems said I was holding a consistent 83* at 70mph & my TVR gauge with the Range Rover sender mod was spot on with this true reading.

This is where the TVR sender would have been showing a worryingly low 65 - 70*, this demonstrates just how misleading it is.

In sumary the Range Rover sender mod while not perfect is a vast improvement over continuing to use the hopeless TVR sender.

You do need to spend some time tuning your variable resistor & I expect the relationship between the gauge & Range Rover sender will be slightly different on every car.

But once you get it right you will have a much more accurate & reliable temperature gauge.

A highly recommended mod in my humble opinion, & thanks to Alex for bringing to my attention

Edited by ChimpofDarkness on Sunday 5th August 21:23

[Ribol]

David Beer who first worked this out reckoned that a 200 ohm variable was the way to go:

http://pistonheads.co.uk/gassing/topic.asp?h=0&amp...

[ChimpofDarkness]

Well whoever discovered it first is somewhat irrelevant, but I guess they do deserve a pat on the back because the point is it works extremely well.

Actually given 170 Ohms seems to give 85* on the TVR gauge, a 0-200 Ohm variable resistor would probably be easier to tune than my 0-1000 Ohm one.

I would want to do some safety tests on it first though, just to make sure it allowed the TVR gauge to rise to say 100*.

After all it's nice to finally have a gauge that's showing the correct running temperature, but if it fails to warn you of a critical coolant temperature rise it's going to be worse than useless.

My guess is a 0-200 Ohm resistor would work fine, 170 Ohms is still 170 Ohms irrespective of the variable resistor's range, but for now I'm happy that my current 0-1000 Ohm resistor shows just such a dangerous situation.

Here are some snaps to show my variable resistor in place, the Range Rover sender position and tuning the variable resistor to the gauge with the help of the Canems software.

Edited by ChimpofDarkness on Monday 6th August 07:57

[Ribol]

ChimpofDarkness said:

.............a 0-200 Ohm variable resistor would probably be easier to tune than my 0-1000 Ohm one........

Correct - hence the reason for pointing it out for anyone doing this.

[sgrimshaw]

ChimpofDarkness said:

Today I did some more testing while running my Canems ECU software that shows the true coolant temperature.

Where is the Canems getting the temperature from?

[ChimpofDarkness]

sgrimshaw said:

Where is the Canems getting the temperature from?

From the same sensor used by the Lucas 14CUX ECU.

The nice thing about the Range Rover sender mod is it's right next to the ECU temp sensor so in theory they should be subject to the same coolant temperature.