external temp sensor on my van

[grstools]

Hi All, my first posting. Don't know much about electronics but here goes. My outside temp sensor has gone bonk, it thinks it is in Marbella instead of cold Huddersfield. Renault want £51 for a new one plus fitting expense. It's a simple affair to get at and change, so can do it myself. Question is, can I use a sensor from another van? my sensor is rated at 2.6kohms at 20C and this new one {£3.50} is 5k ohms. I've connected it, but its not showing a correct temperature. Is it possible to connect a resistor to one end of the sensor to bring it down to 2.6 kohms and work properly?. If not, can I buy a simple 2.6 kohm thermistor and connect it directly or is there some more electrickery here with other components necessary? I'd love to build a reliable one myself and install it. Your advice is appreciated. Regards, Graeme [taxi driver]

[Thomas W]

What is the brand and model number of the new sensor? And the old one? Where did you buy the new one?

[grstools]

Hi Simon, there is no identification on these items. All I know is the resistance value at 20C. Original was 2,600 ohms and this new one is 5,000 ohms. only 2 connections. New one bought from Vauxhall spare parts dealer on ebay. Can I connect a thermistor directly to the wires or do I need other components? Thanks Graeme.

[grstools]

Hi Simon, here is some more information. I have disconnected the sensor. Using my resistance meter i have following results. 20C = 2.6kohms,
0C = 6.0k ohms, 40C = 1.5kohms. when I connect meter at hot or cold temperature and watch the meter, it goes up or down steadily till reaching room temperature resistance value.. It looks like the sensor is working ok????? When I connect to van it reads 32C and slowly goes down to 13C. Nothing else, so something is wrong. With sensor connected I get reading of 1.1 volt and as the reading starts to drop the voltage moves up, but only very slowly. Graeme.

[Thomas W]

Do you have a Haynes repair manual for your van? If there is one it may have a description of the sensor system, and ways to repair and test it.
Did you measure the old sensor, or the new one? I assume the numbers 6.0k, 2.6k and 1.5k are from the old one.
Regards, Thomas.

[grstools]

Hi Thomas, I don't think Haynes would have such technical info in it. The readings are from original Renault sensor and the resistance seems to alter with change in temp.. so it should work. I only have 2.0 vdc supply with sensor disconnected. Could this be the problem? Any idea what voltage should be present. Graeme.

[Thomas W]

What model and year is your Renault van?
What readings do you get if you measure the new sensor? (0 C, 20 C, 40 C)
There are many ways to design such a sensor circuit, so in order to verify the voltage a schematic would be needed, or a repair description. Contacting the support team at Renault could also be an option.