Weird fault in temperature gauge

[norimus]

Hi Everyone !
I've had some troubles with my temperature gauge and thinking that it was the temperature sender i've changed it.. all good and it works.. checked it with a multimeter on cold and hot. and it works ok..
The temperature gauge is still not working.. but get this.. if I ground the single wire that goes to the gauge.. the indication jumps to hot.. meaning that the dash indication "should work".The sender does not ground through the threads though.Since it has two connections, I have measured between the two pins and that is where the variation occurs.. all good again.I thought to myself.. easy, i'll connect the single wire from the gauge to one of the pins and the other one I'll ground directly to the battery to make sure that it works, all for testing purposes.. still no variation on the gauge.. it really seems like the gauge can only indicate C(or open contact) and H (or dead short).Has anyone seen this before ? Could it be such a fault in the gauge ? (no middle indication only the extremes !!!) If so, would you think of changing it ? Thanks in advance for any suggestion and thought...

N

 

[bobflood]

Which engine do you have? I have seen some posts that indicate that on some engines there are two temp senders located right beside each other in the thermostat housing - one with a single wire and one with two wires. One of them drives the guage, the other one the ECU (don't remember which is which). You may be working with the wrong one. You might want to do a search to find the relevant threads.

 

[budwich]

X2.... the gage uses on a single wire sender. You got or are working with the wrong sender.

 

[norimus]

Hi guys ! Well.. I am definitely working on the right one because as I was saying, when I ground the wire coming from the dash the gauge goes to H.. I have also used a trimpot to prove the variation and it seems to be all ok.. furthermore, I have measured the resistance between the two pins of the sender and it does vary in accordance with the resistance/temperature dependance chart which I have found on this forum.. the bizarre thing is that the gauge would not move no matter what.. that is weird ...

 

[budwich]

BUT... someone likely put in the wrong sender unit. The "right one" should be grounded to the engine.... hence the single wire. OF course, your "investigation" is excellent.... having said that you didn't indicate what value of trim pot you used to test your "theory" AND you didn't indicate what resistance values you are reading from the existing sensor. I suspect that you will find that the values are such that "insufficient" current flows to allow the meter to operate... meaning the resistance is too high.... just my guess. But upon re-reading your last post, ultimately I would like to know how you are converting the "two wire sensor" to a "single wire" operation??? your answer likely lies there. Still further, what value of voltage are you reading (open "circuit") on the single wire AND in your "converted two wire operation"?????

PS... Of course, everything that I said is "right side up" for North American as opposed to you "poor sods" down under ... but I can only assume still holds to some degree (ie. single wire is single wire)