Range Rover Temp Sender Thread Size?
Discussion
Hi all,
Can someone 100% confirm the thread size for what is commonly referred to in TVR circles as the Range Rover temp sender?
I believe the above Range Rover temp sender marked with a green arrow has a 1/8 NPT thread?
If I'm correct I may have located a 1/8 NPT sender with the exact same resistance qualities to match the original Caerbont coolant temperature gauge used in the majority of Chimaeras and Griffiths. This would allow Chimaera and Griffith owners to simply remove the redundant Range Rover temp sender TVR never used and replace it with a 1/8 NPT threaded sender that has the exact same resistance characteristics as the original 5/8 UNF threaded sender TVR used.
For those who are unaware of the problem I should explain; because TVR used a sender with 5/8 UNF thread they were forced to fit in an adapter which is well known to give inconsistent readings, the adapter is effectively a dead end spur so water contact and circulation around the sender is very poor.
As a work around for years TVR owners (myself included) have used a resistor on the Range Rover temp sender like this....
However recently I had cause to test this resistor idea, I had a temporary radiator fan failure caused by one on those nasty cheap waterproof fuse holders I have come to dislike so much, at idle with no fans I noticed the temperature reading on my Canems software was heading to and past the 100c point with the digital reading on my Davies Craig fan controller showing the same.
However my TVR temperature gauge running the Range Rover temp sender and resistor mod was still displaying 90c
Quite clearly the resistor mod is a dangerous idea, a temperature gauge that rises to 90c normally is fine but one that stops there no matter how hot the coolant becomes is actually worse than useless as you think you're at 90c when the engine is actually dangerously overheating.
So if someone can come on to confirm 100% that the Range Rover temp sender has a 1/8 NPT thread we may well have ourselves a solution that will solve the problem of poor and inconsistent temperature gauge readings on our Caerbont gauge equipped Chims & Griffs..... and solve properly this time!
Thanks, Dave.
Can someone 100% confirm the thread size for what is commonly referred to in TVR circles as the Range Rover temp sender?
I believe the above Range Rover temp sender marked with a green arrow has a 1/8 NPT thread?
If I'm correct I may have located a 1/8 NPT sender with the exact same resistance qualities to match the original Caerbont coolant temperature gauge used in the majority of Chimaeras and Griffiths. This would allow Chimaera and Griffith owners to simply remove the redundant Range Rover temp sender TVR never used and replace it with a 1/8 NPT threaded sender that has the exact same resistance characteristics as the original 5/8 UNF threaded sender TVR used.
For those who are unaware of the problem I should explain; because TVR used a sender with 5/8 UNF thread they were forced to fit in an adapter which is well known to give inconsistent readings, the adapter is effectively a dead end spur so water contact and circulation around the sender is very poor.
As a work around for years TVR owners (myself included) have used a resistor on the Range Rover temp sender like this....
However recently I had cause to test this resistor idea, I had a temporary radiator fan failure caused by one on those nasty cheap waterproof fuse holders I have come to dislike so much, at idle with no fans I noticed the temperature reading on my Canems software was heading to and past the 100c point with the digital reading on my Davies Craig fan controller showing the same.
However my TVR temperature gauge running the Range Rover temp sender and resistor mod was still displaying 90c
Quite clearly the resistor mod is a dangerous idea, a temperature gauge that rises to 90c normally is fine but one that stops there no matter how hot the coolant becomes is actually worse than useless as you think you're at 90c when the engine is actually dangerously overheating.
So if someone can come on to confirm 100% that the Range Rover temp sender has a 1/8 NPT thread we may well have ourselves a solution that will solve the problem of poor and inconsistent temperature gauge readings on our Caerbont gauge equipped Chims & Griffs..... and solve properly this time!
Thanks, Dave.
Yep 1/8npt, however I ditched the crappy sender, drilled out to m10x1 , installed a PT100 sensor, fitted the spyda converter box and now have a calibrated temperature readout at all temperatures. Makes you wonder why they never fitted a sender to match the gauge in that position in the first place.
Edited by hoofa on Tuesday 18th June 18:25
Ok thanks chaps 
I was also 99% sure the so called Range Rover sender has a 1/8 NPT thread but appreciate the double confirmation from Bobfather and hoofa, I will place my order tomorrow and do some testing before releasing the details, I want to be sure the sender I've identified does indeed deliver the results I've been promised.
If all goes well, in the spirit of supporting the TVR community with open source information and rather than attempting to profiteer from my discovery I will make the part number and supplier public on these pages. To be clear fitting the sender will be a simple case of winding out the Range Rover sender and replacing it with the new one that is expected to cost no more than £20 including postage.
With the resistor mod proven to be untrustworthy and a Spyda Design Gauge Wizard selling for £44.00 I'm hoping this easy to install £15.00 sender swap could be the cost effective and straightforward solution to that TVR sender thats stuck in blind hole adapter?
Watch this space
I was also 99% sure the so called Range Rover sender has a 1/8 NPT thread but appreciate the double confirmation from Bobfather and hoofa, I will place my order tomorrow and do some testing before releasing the details, I want to be sure the sender I've identified does indeed deliver the results I've been promised.
If all goes well, in the spirit of supporting the TVR community with open source information and rather than attempting to profiteer from my discovery I will make the part number and supplier public on these pages. To be clear fitting the sender will be a simple case of winding out the Range Rover sender and replacing it with the new one that is expected to cost no more than £20 including postage.
With the resistor mod proven to be untrustworthy and a Spyda Design Gauge Wizard selling for £44.00 I'm hoping this easy to install £15.00 sender swap could be the cost effective and straightforward solution to that TVR sender thats stuck in blind hole adapter?
Watch this space
I drilled and tapped the original gauge sensor adaptor hole to 5/8" NPT, thereby moving the sensor into the waterway. There was no discernible difference in the gauge reading before and after.
The accuracy of the gauge is now confirmed with a new GM sensor mounted in a re-drilled and tapped hole in place of the CUX sensor.
Perhaps the inconsistent readings mentioned are unrelated to the position of the original gauge sensor.
The accuracy of the gauge is now confirmed with a new GM sensor mounted in a re-drilled and tapped hole in place of the CUX sensor.
Perhaps the inconsistent readings mentioned are unrelated to the position of the original gauge sensor.
ed_crouch said:
So the one-wire gauge sender is 1/8NPT.
The two-wire ecu CTS is threaded M12*1.5. I know this for definite because I was making a reducer bushing for one last night.
The one underneath that needs forgetting about.....no idea.
Excellent, thanks The two-wire ecu CTS is threaded M12*1.5. I know this for definite because I was making a reducer bushing for one last night.
The one underneath that needs forgetting about.....no idea.
I have ordered two senders as this is the minimum order requirement, one I will test in my Chimaera and the other will go to a local friend also with a Chimaera.
So before I release the details of the the new supposedly matched 1/8NPT sender it will have been tested and confirmed to work correctly in two Chimaeras both running the Caerbont gauges.
Lets hope it works
, my resistor mod needs to go as it is not to be trusted 
Good morning all,
Sorry for the long post but it might throw some light on the apparent innaccuracy of Chimaera gauges (Caerbont in my case).
I went through a similar exercise as Dave is doing a couple of years ago, having already replaced the TVR sensor when I first bought the car, and the outcome was "interesting".
My temp gauge readings were very erratic and to my mind low. I put this down to either/all of the usual reasons i.e. sensor broken/airflow/silted up sensor/air pocket/not in a decent waterflow/etc.
Fortunately I had a spare proper unused TVR sensor in stock so plotted its resistance/temp graph. I did the test twice using a saucepan of water from 100 degrees down to room temp, an infrared thermometer and a digital thermometer. Both thermometers gave the same results.
I then sourced an industrial 1/8" NPT sensor with the same resistance curve and checked the restance/temp curve as above before I fitted it. It was the same as the TVR sensor.
Before fitting I tested (a number of times) the gauge reading with the industrial sensor in a saucepan of water from 100 to room temp again measuring water temp with both infrared and digital thermometers. Across the whole range the gauge readings were way out. I tested the TVR sensor and got the same results.
I assumed from these tests that the gauge may need recalibrating or simply replacing so I sent both gauge and industrial sensor off to Speedy Cables who tested both gauge and sensor. Their conclusion was that no sensor with that temp/resistance curve would give a correct temp reading on that gauge. When I told them that it was the same as a TVR sensor, their reply was that the TVR gauge and TVR sensor were mismatched and would never give a correct reading!!! I asked if they could supply a 1/8" NPT sensor that would match the gauge and they couldn't but could put a new movement in the gauge and supply the correct sensor.
I took up this option and, when the bits arrived back, I bench tested again. Gauge reading to thermometer reading were spot on. Subsequently the car went into Southways for a service and they checked gauge temp against ECU temp and they "accurately matched". I got the impression from them that this is unusual.
All in this cost me about £200 but to me it was worth it as I can now be confident that the temp gauge is telling the truth. However a few weeks after this I went ot Switzerland to drive the Andermatt loop but in the tunnels under Zurich the temperature gauge started reading very high, up to ca. 105/110 degrees. The fans were obviously working as I could hear them cutting in and the temp was going up and down with the fans working. I stopped as soon as I could, turned the headlights off and the temperature gauge returned to normal. On turning the headlights on again there was an immediate jump in temp gauge reading of 10 -15 degrees!!! I presume this is because the headlight causes volt drop to the gauges resulting in a higher indicated temperature.
I am not sugesting that this is an inherent problem with the choice of sensor and gauge made by TVR, but it does seem odd that the original sensor when I bought the car, the replacement I fitted to try to fix the problem, a spare I bought to replace the replacement sensor and an industrial sensor with the same temp curve all displayed the same low gauge temperature readings. All I know is that with a matched gauge and sensor the displayed temperature is correct.
I hope this helps
All the best
Dick
Sorry for the long post but it might throw some light on the apparent innaccuracy of Chimaera gauges (Caerbont in my case).
I went through a similar exercise as Dave is doing a couple of years ago, having already replaced the TVR sensor when I first bought the car, and the outcome was "interesting".
My temp gauge readings were very erratic and to my mind low. I put this down to either/all of the usual reasons i.e. sensor broken/airflow/silted up sensor/air pocket/not in a decent waterflow/etc.
Fortunately I had a spare proper unused TVR sensor in stock so plotted its resistance/temp graph. I did the test twice using a saucepan of water from 100 degrees down to room temp, an infrared thermometer and a digital thermometer. Both thermometers gave the same results.
I then sourced an industrial 1/8" NPT sensor with the same resistance curve and checked the restance/temp curve as above before I fitted it. It was the same as the TVR sensor.
Before fitting I tested (a number of times) the gauge reading with the industrial sensor in a saucepan of water from 100 to room temp again measuring water temp with both infrared and digital thermometers. Across the whole range the gauge readings were way out. I tested the TVR sensor and got the same results.
I assumed from these tests that the gauge may need recalibrating or simply replacing so I sent both gauge and industrial sensor off to Speedy Cables who tested both gauge and sensor. Their conclusion was that no sensor with that temp/resistance curve would give a correct temp reading on that gauge. When I told them that it was the same as a TVR sensor, their reply was that the TVR gauge and TVR sensor were mismatched and would never give a correct reading!!! I asked if they could supply a 1/8" NPT sensor that would match the gauge and they couldn't but could put a new movement in the gauge and supply the correct sensor.
I took up this option and, when the bits arrived back, I bench tested again. Gauge reading to thermometer reading were spot on. Subsequently the car went into Southways for a service and they checked gauge temp against ECU temp and they "accurately matched". I got the impression from them that this is unusual.
All in this cost me about £200 but to me it was worth it as I can now be confident that the temp gauge is telling the truth. However a few weeks after this I went ot Switzerland to drive the Andermatt loop but in the tunnels under Zurich the temperature gauge started reading very high, up to ca. 105/110 degrees. The fans were obviously working as I could hear them cutting in and the temp was going up and down with the fans working. I stopped as soon as I could, turned the headlights off and the temperature gauge returned to normal. On turning the headlights on again there was an immediate jump in temp gauge reading of 10 -15 degrees!!! I presume this is because the headlight causes volt drop to the gauges resulting in a higher indicated temperature.
I am not sugesting that this is an inherent problem with the choice of sensor and gauge made by TVR, but it does seem odd that the original sensor when I bought the car, the replacement I fitted to try to fix the problem, a spare I bought to replace the replacement sensor and an industrial sensor with the same temp curve all displayed the same low gauge temperature readings. All I know is that with a matched gauge and sensor the displayed temperature is correct.
I hope this helps
All the best
Dick
Yeh I'm doing similar at the moment, but I will be driving the gauges with a microcontroller through the PWM output. I've tested it on the bench and it works a treat. Plus, it means that I can use any sensor I please as I can calibrate the microcontroller to suit. Also, I'll be spitting out sender readings from the megasquirt3 ecu over CANbus and picking them up with the uC.
Thanks Dick (trumpet1608), thats a very comprehensive and well written response but with a concerning conclusion that the gauge and sender were never actually correctly matched in the first place 
It seems I'm following your lead, but as I've just committed to the new sender when it arrives I will test it against my Canems software that gives accurate coolant temp readings and see what results I get.
On the separate point of Chimaera gauges being affected by electrical load I too can confirm if the earthing on the car is not spot on the gauges are the first to show you, I recently found the following poor connections at both my battery terminals others had missed.
After correcting the issues illumination of all the gauges became brighter and their reading became more accurate too.
I suspect the reason for your temp gauge over reading with the headlights on was due to the poor grounding that can plague these cars, being sensitive instruments the gauges by their very nature are also very sensitive to grounding issues and voltage drops within the car's electrical loom.
And because they are gauges the driver gets to see a clear visual representation of these issues
It seems I'm following your lead, but as I've just committed to the new sender when it arrives I will test it against my Canems software that gives accurate coolant temp readings and see what results I get.
On the separate point of Chimaera gauges being affected by electrical load I too can confirm if the earthing on the car is not spot on the gauges are the first to show you, I recently found the following poor connections at both my battery terminals others had missed.
After correcting the issues illumination of all the gauges became brighter and their reading became more accurate too.
I suspect the reason for your temp gauge over reading with the headlights on was due to the poor grounding that can plague these cars, being sensitive instruments the gauges by their very nature are also very sensitive to grounding issues and voltage drops within the car's electrical loom.
And because they are gauges the driver gets to see a clear visual representation of these issues
ed_crouch said:
Yeh I'm doing similar at the moment, but I will be driving the gauges with a microcontroller through the PWM output. I've tested it on the bench and it works a treat. Plus, it means that I can use any sensor I please as I can calibrate the microcontroller to suit. Also, I'll be spitting out sender readings from the megasquirt3 ecu over CANbus and picking them up with the uC.
Out of interest what microcontroller are you using, also can you do a multipoint calibration ?? I have been using a PT100 probe and the spyda box. I have both a decade box and hotwell calibrator to check the probe against a set temperature right the way through the gauge temps. Would be good to see what your using. Dave, Dick and Nigel (and all the others), this makes fascinating reading, and a big thank you from me for making your combined knowledge public.
I am presently on the Range Rover sender with variable resistor, but can confirm that on a recent track day my water temperature gauge was only at 80-90 degrees, at a time that my recently fitted Caerbont oil temperature gauge was shouting “Stop” at well over 115 degrees C. Part of the problem was my schoolboy error at the start of the day.......I got the car and myself ready, but was too busy chatting to friends and completely forgot to remove my front number plate, thus reducing the cooling airflow. I have now relocated the numberplate out of the airflow, so I no longer need to remove it.
To my mind it is only at times of high temperatures that these gauges really matter, and having previously noticed that my water temp gauge was not telling me anything useful, I am after a more truthful set up regardless of cost - a new engine costs a damn sight more!
Our mutual friend Peter (Phazed) has a twin oil and water temp Spa gauge fitted in his car. Horror of horrors, it doesn’t match the other gauges, but it does give digital readouts of both temperatures and employs its own senders I believe, which presumably are matched to the gauge. It also can be set to flash red at any temperature that the owner thinks it would be relevant to be warned there is a problem.
What does the collective brain power on this thread think of my present thought that I should fit a Spa gauge (or two separate Spa gauges)?
I am presently on the Range Rover sender with variable resistor, but can confirm that on a recent track day my water temperature gauge was only at 80-90 degrees, at a time that my recently fitted Caerbont oil temperature gauge was shouting “Stop” at well over 115 degrees C. Part of the problem was my schoolboy error at the start of the day.......I got the car and myself ready, but was too busy chatting to friends and completely forgot to remove my front number plate, thus reducing the cooling airflow. I have now relocated the numberplate out of the airflow, so I no longer need to remove it.
To my mind it is only at times of high temperatures that these gauges really matter, and having previously noticed that my water temp gauge was not telling me anything useful, I am after a more truthful set up regardless of cost - a new engine costs a damn sight more!
Our mutual friend Peter (Phazed) has a twin oil and water temp Spa gauge fitted in his car. Horror of horrors, it doesn’t match the other gauges, but it does give digital readouts of both temperatures and employs its own senders I believe, which presumably are matched to the gauge. It also can be set to flash red at any temperature that the owner thinks it would be relevant to be warned there is a problem.
What does the collective brain power on this thread think of my present thought that I should fit a Spa gauge (or two separate Spa gauges)?
LLantrisant said:
sorry to hi-jack this thread:
could it be that pre-serpentine engines do NOT have this rover sensors installed, neither a thread in that area? just the ECU sensor and beisdes of it a casted unthreaded boss?
That's correct. Pre interim manifolds have a different gauge sensor and it's mounted as belowcould it be that pre-serpentine engines do NOT have this rover sensors installed, neither a thread in that area? just the ECU sensor and beisdes of it a casted unthreaded boss?
Dougal.
QBee said:
Dave, Dick and Nigel (and all the others), this makes fascinating reading, and a big thank you from me for making your combined knowledge public.
I am presently on the Range Rover sender with variable resistor, but can confirm that on a recent track day my water temperature gauge was only at 80-90 degrees, at a time that my recently fitted Caerbont oil temperature gauge was shouting “Stop” at well over 115 degrees C. Part of the problem was my schoolboy error at the start of the day.......I got the car and myself ready, but was too busy chatting to friends and completely forgot to remove my front number plate, thus reducing the cooling airflow. I have now relocated the numberplate out of the airflow, so I no longer need to remove it.
To my mind it is only at times of high temperatures that these gauges really matter, and having previously noticed that my water temp gauge was not telling me anything useful, I am after a more truthful set up regardless of cost - a new engine costs a damn sight more!
Our mutual friend Peter (Phazed) has a twin oil and water temp Spa gauge fitted in his car. Horror of horrors, it doesn’t match the other gauges, but it does give digital readouts of both temperatures and employs its own senders I believe, which presumably are matched to the gauge. It also can be set to flash red at any temperature that the owner thinks it would be relevant to be warned there is a problem.
What does the collective brain power on this thread think of my present thought that I should fit a Spa gauge (or two separate Spa gauges)?
Can’t argue with that. I am presently on the Range Rover sender with variable resistor, but can confirm that on a recent track day my water temperature gauge was only at 80-90 degrees, at a time that my recently fitted Caerbont oil temperature gauge was shouting “Stop” at well over 115 degrees C. Part of the problem was my schoolboy error at the start of the day.......I got the car and myself ready, but was too busy chatting to friends and completely forgot to remove my front number plate, thus reducing the cooling airflow. I have now relocated the numberplate out of the airflow, so I no longer need to remove it.
To my mind it is only at times of high temperatures that these gauges really matter, and having previously noticed that my water temp gauge was not telling me anything useful, I am after a more truthful set up regardless of cost - a new engine costs a damn sight more!
Our mutual friend Peter (Phazed) has a twin oil and water temp Spa gauge fitted in his car. Horror of horrors, it doesn’t match the other gauges, but it does give digital readouts of both temperatures and employs its own senders I believe, which presumably are matched to the gauge. It also can be set to flash red at any temperature that the owner thinks it would be relevant to be warned there is a problem.
What does the collective brain power on this thread think of my present thought that I should fit a Spa gauge (or two separate Spa gauges)?
The only thing I’d note is 115d for oil temp is fairly normal on track id have thought and not an indication that you are over heating,,, more the friction you are causing with your right foot.
Oil temp being critical would have me wanting an oil temp gauge with a sender that’s fitted in a place that can give accurate readings.
I’d suggest many a driver sat in traffic in South of France has had oil temps rising to well over 100d and probably on many occasions.
Engine builder always told me on track 115 with good oil is just about ok, 120 and above would be iffy so you are right to be considering this.
I noticed Powers have added the small (racers) screen on one of their Ecu installs the other day, this is a brilliant bit of kit that can give you all the info you need and flags things up if going out of your pre set windows,,,
I’d like to think other Ecu can offer a similar solution, after all its only like having the laptop plugged in.
If I had a miraculous life turn around
and did trackdays for kicks I would/will invest in the latest MBE ECU and the small compact screen I mention as to me that’s going to give far more accurate readings as its using the same info the Ecu does. Forget trackdays, traffic is enough to have me wanting to protect my rebuilt engine so this is like a no brainier, I don’t know if it’s available on other platforms but it should be.
Most single seater race car uses these small robust screens inside a 10inch steering wheel as they can’t afford the room for lots of gauges so it’s not like they are not available on some aftermarket Ecu.
This tool could save you a small fortune if you think about it.
Dougal9887 said:
Megasquirt uses a display called shadow dash which displays all the info over bluetooth on your mobile device. This is very convenient as smart phones are very often in use for navigation etc, so all the info is available for the cost of a serial connection bluetooth device.
Dougal.
Very good use of a tool already in use. Dougal.
It’s the way forward and something any tuned engine owner should be looking at mainly for his own sanity
The more I can leave things looking original matters to me so things like this can be good additions without having to alter the looks. It’s kind of very cool to be able to use computers on such old engined cars and keep up with modern diagnostics and information streams.
How many race engines and crashes have been saved because drivers had flashing lights telling them something very wrong is about to happen, the days of cars dumping oil on race tracks is actually quite rare and probably because of tools like these.
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