Need some mechanic help

[mortatone]

2002 Nissan Sentra 1.8L basic model.

Googling isn't helping. Maybe I need a Haynes manual.

Basically what I want to know is how the temp gauge on the dashboard gets its info. I know there's a temp sensor that provides info to control 2 multi-speed fans but does it also provide that info directly to the temp gauge in the dash or is there another sensor that informs the dash gauge?

I think I'm getting false readings at the dash gauge and I've already replaced the tstat and the sensor that I know controls the fans. I was told that it also informs the dash gauge but that may or may not be correct. When the sensor is disconnected during operation, the cooling fans default to high speed but the dash gauge doesn't react. Is there another sensor?

(Yes there's plenty of coolant, no leaks, and I can keep my hand on the radiator cap during a false hot reading and the outlet temp of the radiator ranges from 120F - 155F so I'm nearly certain that there's not an actual cooling problem. Just got home from a 450 mile drive and at the very end of it got a false hot reading and I could keep my hand on the radiator cap and radiator outlet hose during it. )

[clipless bumper]

I found this post that says there are 2 different sensors.

I don't usually trust Yahoo answers, but.....

[mortatone]

I found this post that says there are 2 different sensors.

I don't usually trust Yahoo answers, but.....

As a matter of fact I do see a small sensor head on the other side of the manifold with one wire going to it, just southwest of where the thermostat lives. Can't find it on the nissan parts page though...

https://parts.nissanusa.com/nissanparts ... &siteid=14

[clipless bumper]

I 'think' the part number/manufacturer is TS-391/Standard - but I can't confirm that 100%

[mortatone]

Looks about like it. I finally found a nissan part number 25080x under the "body electrical" section.

[clipless bumper]

Pretty sure that's it - found it again in the Standard website

https://ecatalog.smpcorp.com/STD/

Check off 'sender temperature w/gauge'

[mortatone]

Yep. Thanks for the help. I had been told by 3 different parts guys that the temp sensor was the only sensor but kept doubting it and couldn't find where it would even be on the engine. It's got a sneaky little hiding spot.

[clipless bumper]

Yeah - for some reason that was a tough one to find. I work weekends at Pro Boys, and I bet our system wouldn't show it easily either.

[mortatone]

Fuck. This is starting to piss me off. Replaced the sender last night and this morning it’s still doing it. I’m not even sure what to look at now, other than to do a temp test on it just to make sure once again that it’s not actually overheating. Any ideas?

[clipless bumper]

make sure you don't have any air in the system - a pocket of air at a sender can cause false readings.
not sure how to do that on that engine - but you need to find the highest point on the system, and fill from there.
Air should work it's own way out - but sometimes doesn't.
Do you have heat inside the vehicle as normal?

[mortatone]

Heat and AC haven’t worked for a long time

[clipless bumper]

do you have the heater core bypassed?
that would take of the problem if the core is air locked, or clogged.

[ajaxlepinski]

Maybe the temp gauge, on the dash, is defective?