4K Water temp sensors - why two???

[Jammcn07]

My KE38 wagon has a 4K in it.

It Has a few gauge issues that I thought I’d iron out, but it’s not quite as easy as i initially thought.

Number 1: Why does my car have two water temp sensors?? And do I need them both??

 

[altezzaclub]

Post up a photo.. 

I can't think of why you'd need two, are they the same units? 

Are they both wired in? Where do the wires go?

Does it have an electric fan? You use a second sensor for those.

[Banjo]

Hi Jamie,

                 Welcome aboard !   A quick picture posted here would help us identify your issue.

Usually there is only one temperature sensor, with an electrical wire attached, which is for the dash temp guage. There are often one or two temp sensors that are not electrically connected, but are actually valves, or switches associated with the  Californian emissions controls on the carby. They had rubber hoses connected to them originally.  Most Rolla users have either removed these, & plugged the hole.

 

Have a read of Altezzaclub's post in the following thread.  Might help.

https://www.rollaclub.com/board/topic/54569-4k-carb-setup/

Cheers Banjo

Edited July 5, 2019 by Banjo

[Jammcn07]

Hey guys, 

 

please seebelow pics pics of the two sensors.

the obvious one is the top side which sits on the carby side of the water inlet housing just under the thermostat inlet.

The second is is on the dizzy side of the water inlet housing and slightly lower down and closer to the head. It was this wire I have traced back I to the dash is connected to the water temp gauge. 

 

So, what I’ve done since is connected the wires from both sensors (after changing the top one), taken that wire back Into the dash and to the water temp gauge. 

Warmed it up and all seemed to work correctly. I’ll take it for a drive tomorrow then tidy things up

[altezzaclub]

Usually we have a vacuum switch on the carb side there, the dizzy side is the temp gauge. Do you think the dizzy side one broke? I don't think it should look like this-

and they replaced it with the carb-side one that works?

Anyway, it works...  You can put a thermometer in the radiator top when its cold and just let it idle until it warms up, so you can check what temperature is which mark on the gauge. There has been many a head gasket blown from a gauge that said "half" when the motor said "boiling!"

If you have both on the temp gauge, it should read twice as hot as it is, although I don't expect them to be the same units so they probably have different resistances. You could measure their resistance when cold, and again when hot, and see if they work the same.

[Jammcn07]

That’s my temp soldering job to that sensor as I didn’t have the right spade cup to fit it correctly. 

 

I replaced the top sensor, that Brought the temp gauge up to maybe quarter temp. Then I brought the wire for the bottom sensor to the same wire as the top and now I’m getting the full reading.

almost as as if one sensor is low temp and the other is the mid to high temp range.

 

now onto the dodgy fuel gauge.......

[altezzaclub]

That is pretty strange, do both of them give a 100% hot gauge reading if you earth the sensors out one at a time?