Barmy temp guage
Discussion
Getting to know the 'charming character' of my car. 
Yesterday while driving slowly in traffic, I was alarmed to see the temp guage going over 100, and staying there even though I put the fans overide on. When I stopped the car about 10 minutes later with the fans off, it took a couple of minutes for both the fans both came on, while the guage still read 105 and they turned off about a minute later, but the temp guage still reading the same.
So to check this, this morning I connected the Roverguage and according to the temp guage in the software, the fans both come on at 95, and turn off at 88. Which I understand is fine. I checked the coolant levels when cold, full in the swirl tank and clear, about 1/3 full in the expansion tank. So it didn't overheat.
While doing the roverguage test, the temp guage inside the car moved up to 85 when the fans came on, but went on to about 95 and stayed there regardless of what the roverguage temp was saying. When the fans turned back off, the guage didnt move back down from 95.
I then turned on the fan overide switch and cooled the engine down to 75 on the roverguage but the temp guage didnt move and stayed where it is at 95. When I then turned the car off and immediately turned it on again the temp guage then read 70.
Reading some threads it seems to be a common problem, but is there a way to get the temp guage to read the actual temperature on these cars?
Yesterday while driving slowly in traffic, I was alarmed to see the temp guage going over 100, and staying there even though I put the fans overide on. When I stopped the car about 10 minutes later with the fans off, it took a couple of minutes for both the fans both came on, while the guage still read 105 and they turned off about a minute later, but the temp guage still reading the same.
So to check this, this morning I connected the Roverguage and according to the temp guage in the software, the fans both come on at 95, and turn off at 88. Which I understand is fine. I checked the coolant levels when cold, full in the swirl tank and clear, about 1/3 full in the expansion tank. So it didn't overheat.
While doing the roverguage test, the temp guage inside the car moved up to 85 when the fans came on, but went on to about 95 and stayed there regardless of what the roverguage temp was saying. When the fans turned back off, the guage didnt move back down from 95.
I then turned on the fan overide switch and cooled the engine down to 75 on the roverguage but the temp guage didnt move and stayed where it is at 95. When I then turned the car off and immediately turned it on again the temp guage then read 70.
Reading some threads it seems to be a common problem, but is there a way to get the temp guage to read the actual temperature on these cars?
There was a discussion about accuracy and that appears to have been settled in favour of the resistor. When you say 'accurate' you may be expecting too much, the sensor and the gauge were constructed to give an indication of temperature, not an perfectly calibrated reading. The benefits of this mod are two fold, your dash gauge will rise and fall in response to temperature changes in the coolant passing that point and it will respond in harmony to the ECU temperature reading. The old TVR sender was never able to detect changes easily because it is situated in a dead spot where coolant does not flow.
You can make the gauge reading identical to the ECU reading at normal running temperature by fitting a variable resistor which will allow you to adjust the gauge reading. That said the ECU reading is not perfectly calibrated either. It is important to understand that coolant temperature in a hot engine varies depending on where in the system you take the reading. The ECU only uses this reading to inform the fuel map that the car is at running temperature, the absolute numbers are not that relevant due to the wide variation in coolant temperatures around the system.
The bottom line is that this mod ensures you will see rising and falling temperature as the coolant temperature changes and it will be able to quickly indicate over temperature
You can make the gauge reading identical to the ECU reading at normal running temperature by fitting a variable resistor which will allow you to adjust the gauge reading. That said the ECU reading is not perfectly calibrated either. It is important to understand that coolant temperature in a hot engine varies depending on where in the system you take the reading. The ECU only uses this reading to inform the fuel map that the car is at running temperature, the absolute numbers are not that relevant due to the wide variation in coolant temperatures around the system.
The bottom line is that this mod ensures you will see rising and falling temperature as the coolant temperature changes and it will be able to quickly indicate over temperature
This one will do, just pre-set it to 170 Ohm and then use it to trim in the gauge reading. Once done I would suggest you fine a way to protect the resistor from heat and moisture as both will cause the resistor to deteriorate.
http://www.ebay.co.uk/itm/NEW-2-x-200-ohm-3362P-1-...
You could remove variable resistor once you have a satisfactory gauge reading, check the Ohm value on a multimeter and then search eBay for a fixed resistor of that value. That way you'll have a resistor that can cope with its environment
http://www.ebay.co.uk/itm/NEW-2-x-200-ohm-3362P-1-...
You could remove variable resistor once you have a satisfactory gauge reading, check the Ohm value on a multimeter and then search eBay for a fixed resistor of that value. That way you'll have a resistor that can cope with its environment
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