Extra water temp sensor

[taznuv]

Hi all, I have a 1980 Alfasud which only has a water temp warning light. I want to have a temperature gauge but the sensor on this is just a thermo switch. I am planning on using a small LCD display to show temp and other data (volts, oil pressure etc), based on something I have already developed using a PIC microcontroller.

To get to the point: how can I easily add an extra sensor that will give me a variable resistance that I can use? Is there something I can slip under a hose, and if so where should I look to put it?

thanks

Bruce

[wildoliver]

I've seen hose inserts where you split the hose and fit it in the centre, also seen people slip a thermocouple under the rubber where the hose goes on to the rad seems like a bad idea to me, can you not just swap the temp switch for a proper sender?

[taznuv]

Cheers for the reply. Yes I think I might be able to change to a proper sender, although it's a strange little unit fitted to one of the cylinder heads. Also I would lose the temp light although I guess that's not a big problem.

[GreenV8S]

The ideal place to plumb in your new sensor is the engine outlet upstream of the stat. Do you have access to a casting or hoses there where you could insert your new sensor? The ones I've seen have been generic thermisters with a screw-in body that can be fitted into any suitable tapped hole. You could drill and tap your own hole in any suitable casting if you felt like it. I used a hose insert which is basically a sleeve which is fitted inline with one of the hoses (top hose in my case) with a threaded boss suitable to take a standard metric sensor. They're available in various sizes for a few quid.

[taznuv]

Thanks for your reply, sounds like a good reliable solution. I've also been told today that on the cars that had a guage they didn't replace the temp switch on the o/s head with a proper sender as I thought, but fitted the extra sender somewhere on the inlet manifold, so I'll have a look tonight and see if I can find a blanking plug anywhere.

[anonymous-user]

i would recommend trying to get the sensor in "Pre-stat" as post stat top hose will only read accurately when the stat is open (and will jump all over the place as the stat cycles) also, if the stat fails shut (with is possible) it won't show the engine over heating at all!

Otherwise, use the sensor as a CHT (cylinder head temp) sensor, reading directly the metal temp of the cylinder head, that way it even works if you loose all the coolant!