RV8 Temp sender variable resistor mod
Discussion
Hi all, as my car is only reading around 60 degrees on the move in this cold weather, I reckon first port of call in checking if there is a genuine problem is to do the sender mod and use the LR one with a resistor. Popular opinion seems to be that I need a 200ohm variable - I am at a loss with electronic components, can anybody tell me if this is what I need? http://www.maplin.co.uk/Search.aspx?criteria=UF98G... part number UF98G (220)
If it's not the right one, could someone in the know give me a link or part number for the correct item please? Thanks!
If it's not the right one, could someone in the know give me a link or part number for the correct item please? Thanks!
Slacey said:
I'm just annoyed by the artificially low reading from the crappy air-cooled TVR sender location.
Although you have no way of knowing whether it's the crappy air-cooled sender location, or the engine really is running cold. Both are perfectly credible causes for the low reading.Fair enough, I'm not trying to be awkward but not having access to an IR thermometer or similar this would be a quick and cheap way of at least eliminating a 'major' problem and proving the sender is faulty or just being cooled artificially.
Andy - thanks for that, I'll let you know when I get them.
Andy - thanks for that, I'll let you know when I get them.
I have been getting the bits together for this mod myself although I am not really up on this sort of thing but this post http://www.pistonheads.com/gassing/topic.asp?h=0&a... says the resistor must be rated as 2 Watts (search for "what sensor" if the link doesn't work)which is not the case for the one you are suggesting, Maplin told me they did not do a 2 Watt variable resistor so I am still looking for a part No. & where to buy such a resistor.
Hopefully someone will come along with some better info shortly.
Hopefully someone will come along with some better info shortly.
You may Just want to test the sensor, in hot water. please find below all the info I have found on the RV8 Temp sensors.
Well the thermotime seem to only control the Cold start injector, and I have this disconnected.
So just a very expensive plug.
I found this info
According to the Rover Efi technician training manual the Efi temp sensor
has the following profile.
TEMP-------OHMS
-10°C------9100 to 9300
0°C-------- 5700 to 5900
20°C-------2400 to 2600
40°C-------1100 to 1300
60°C-------500 to 700
80°C-------300 to 400
100°C------150 to 200
also these graphs.
This seems to match gauge sensor.
This seems to match the above Efi info
Ok I took my Sensors off to do some tests, with known water temp's
Brown Sensor seem to be a switch as such under 35oC its 50 Ohms and above its 220 Ohms.
Black sensor readings
30oC 2k Ohms
35oC 1.5 K Ohms
60oC 500 Ohms
70oC 445 Ohms
80oC 260 Ohms
100oC 200 Ohms
Main Temp Sensor that goes to the Gauge.
30oC 460 Ohms
35oC 390 Ohms
60oC 190 Ohms
70oC 225 Ohms
80oC 154 Ohms
83oC 147 Ohms
85oC 140 Ohms
90oC 137 Ohms
95oC 120 Ohms
Had a problems getting a stable 100oC
I will get some varible resisters and set at the same value to see what the gauge reads at the above values.
This way I know what my actual gauge reads with my sensors and know how far out it is. I can also make my own CD marker marks on the gauge for 80 - 90 and 95. this way I should have an exact way of knowing what the tempture is, within 2 or 3 degres.
Well the thermotime seem to only control the Cold start injector, and I have this disconnected.
So just a very expensive plug.
I found this info
According to the Rover Efi technician training manual the Efi temp sensor
has the following profile.
TEMP-------OHMS
-10°C------9100 to 9300
0°C-------- 5700 to 5900
20°C-------2400 to 2600
40°C-------1100 to 1300
60°C-------500 to 700
80°C-------300 to 400
100°C------150 to 200
also these graphs.
This seems to match gauge sensor.
This seems to match the above Efi info
Ok I took my Sensors off to do some tests, with known water temp's
Brown Sensor seem to be a switch as such under 35oC its 50 Ohms and above its 220 Ohms.
Black sensor readings
30oC 2k Ohms
35oC 1.5 K Ohms
60oC 500 Ohms
70oC 445 Ohms
80oC 260 Ohms
100oC 200 Ohms
Main Temp Sensor that goes to the Gauge.
30oC 460 Ohms
35oC 390 Ohms
60oC 190 Ohms
70oC 225 Ohms
80oC 154 Ohms
83oC 147 Ohms
85oC 140 Ohms
90oC 137 Ohms
95oC 120 Ohms
Had a problems getting a stable 100oC
I will get some varible resisters and set at the same value to see what the gauge reads at the above values.
This way I know what my actual gauge reads with my sensors and know how far out it is. I can also make my own CD marker marks on the gauge for 80 - 90 and 95. this way I should have an exact way of knowing what the tempture is, within 2 or 3 degres.
Bear in mind that the car in question is a 96 Griff - no thermotime switch and different instruments and senders than those on a Wedge.
The David Beer mod is only accurate at a point where the added resistance plus the sender resistance matches the original sender value. As the temp changes, the added resistance starts to distort the values and the indicated temperatures start to become more inaccurate. As the temp goes up, the error will increase and the guage will read lower as the resistance becomes the dominant factor. The adjustable resistor allows you the option of adjusting for a point of your choice.
The end result is a gauge that is only accurate at one point and will differ either side of that temperature. No real problem with that as the guage is really only an indicator and not an accurate thermometer. It does really require knowing what the actual temperature is to allow it to be set up so I am not sure it is any real benefit if you use it to try and fault find a possible dodgy sensor. Especially as it could be the gauge is at fault.
To be honest an IR thermometer is a better way of checking temperatures.
The David Beer mod is only accurate at a point where the added resistance plus the sender resistance matches the original sender value. As the temp changes, the added resistance starts to distort the values and the indicated temperatures start to become more inaccurate. As the temp goes up, the error will increase and the guage will read lower as the resistance becomes the dominant factor. The adjustable resistor allows you the option of adjusting for a point of your choice.
The end result is a gauge that is only accurate at one point and will differ either side of that temperature. No real problem with that as the guage is really only an indicator and not an accurate thermometer. It does really require knowing what the actual temperature is to allow it to be set up so I am not sure it is any real benefit if you use it to try and fault find a possible dodgy sensor. Especially as it could be the gauge is at fault.
To be honest an IR thermometer is a better way of checking temperatures.
Edited by shpub on Thursday 3rd January 12:23
The IR thermometer is the only way and remember the top and bottom of the rad will be at different temps..
All you can do is prove to yourself that the car is at a reasonable temperature.
With a car set-up to be able to get rid of large amounts of heat generated by a large V8 - it's overcooled in the winter.
All you can do is prove to yourself that the car is at a reasonable temperature.
With a car set-up to be able to get rid of large amounts of heat generated by a large V8 - it's overcooled in the winter.
shpub said:
Bear in mind that the car in question is a 96 Griff - no thermotime switch and different instruments and senders than those on a Wedge.
Opps I was thinging about the ECR sender.as all the ECU temp senders in the RV8 I have seen with the black top are the same wedge - SD1 landrover, and the latest P38 Dissy less engines.
The maplins IR temp gun works very well and is cheep, so you should def. invest in one.
To follow up on this, I had a go over the weekend. I took a look at the Maplin website and bought an IR thermometer for £25, half price in the sale. I also bought a fixed 180ohm resistor (as we never got a definate part number for the variable resistor on this thread) and made up the little loom necessary.
After taking the car out and getting my usual 60 degree reading on the gauge, I jumped out and took a reading from the TVR sender; a shade over 60. I then took a reading from the LR sender; just over 70 degrees. I then swapped the wire over from the TVR sender to my little loom and the LR sender, the gauge immediately increases to 75 degrees and whilst continuing the journey stayed there - no drop when under way as the original sender reading would. When I got home I left it to idle and let the fans cut in. The gauge said 85 degrees, the IR reading on the LR sender just under 90.
So, the mod does work as far as giving a stable and constant reading either at a standstill or on the move, which is what I was after. In my own head, the fluctuating reading was annoying and put questions in there as to whether there was a problem with the car - which there isn't. I will agree that in the summer, the TVR sender doesn't lie to you due to the warmer ambient air so is perfectly reliable in certain conditions, and that the LR one won't be accurate at anything other than the temp the resistor sets it, but lets face it the gauge is only an indicator, not a precision instrument.
Make of this what you will, but if like me you would prefer a constant reading 99% of the time, for very little money and a little time this is an easy (if not perfect) fix.
After taking the car out and getting my usual 60 degree reading on the gauge, I jumped out and took a reading from the TVR sender; a shade over 60. I then took a reading from the LR sender; just over 70 degrees. I then swapped the wire over from the TVR sender to my little loom and the LR sender, the gauge immediately increases to 75 degrees and whilst continuing the journey stayed there - no drop when under way as the original sender reading would. When I got home I left it to idle and let the fans cut in. The gauge said 85 degrees, the IR reading on the LR sender just under 90.
So, the mod does work as far as giving a stable and constant reading either at a standstill or on the move, which is what I was after. In my own head, the fluctuating reading was annoying and put questions in there as to whether there was a problem with the car - which there isn't. I will agree that in the summer, the TVR sender doesn't lie to you due to the warmer ambient air so is perfectly reliable in certain conditions, and that the LR one won't be accurate at anything other than the temp the resistor sets it, but lets face it the gauge is only an indicator, not a precision instrument.
Make of this what you will, but if like me you would prefer a constant reading 99% of the time, for very little money and a little time this is an easy (if not perfect) fix.
Well it's going to give a constant reading, as it not reading what the car temp is.
As you say the sender only gives you an idea. but I would not replace it. as if you do over heat due to a problem your not going to know until its too late.
The main problem with temp senders is they are not linier, and don't have a straight graph. so unless you get a very expensive or programmable digital gauge, then you will have to have a compromise.
I think you getting your self confused on the ECU sender going faulty and causing the engine to run rough. you can then bypass the sensor so the ECU thinks the engine is hot, etc.
As you say the sender only gives you an idea. but I would not replace it. as if you do over heat due to a problem your not going to know until its too late.
The main problem with temp senders is they are not linier, and don't have a straight graph. so unless you get a very expensive or programmable digital gauge, then you will have to have a compromise.
I think you getting your self confused on the ECU sender going faulty and causing the engine to run rough. you can then bypass the sensor so the ECU thinks the engine is hot, etc.
TVRleigh_BBWR said:
Well it's going to give a constant reading, as it not reading what the car temp is.
Think you've got hold of the wrong end of the stick. He has swapped the guage's signal from a temp sender that is potentially air cooled to one that is tapped into the block but not normally used. It's giving a more repeatable measurement because it isn't being air cooled; it isn't giving a constant measure.Edited by ATG on Tuesday 8th January 11:45
ATG said:
Think you've got hold of the wrong end of the stick. He has swapped the guage's signal from a temp sender that is potentially air cooled to one that is tapped into the block but not normally used. It's giving a more repeatable measurement because it isn't being air cooled; it isn't giving a constant measure.
Exactly that, there is no problem at all with the ECU temp sender which is next to the 'spare' one I am now using.Just noticed this thread, I have just installed an Emerald ECU in mine and along with this, I put in a brand new coolant temp sender in place of the old one which drove the ECU. When I run it up to full temp, the ECU reads pretty accurate and I set it to bring the fans on at 85 which it did just fine. When I looked at the gauge in the car though, it was only reading around 75ish which seemed a bit odd. So does this mean that I should just do this mod and switch to the LR sender with an inline resistor or is it likely that the sensor is faulty? Also, if I was to switch to the LR sensor, would I need to earth the other pin as the normal sensor only has the one but the LR one has 2??
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