Question on Tempature gauge reading

[gqxvietboy]

I got my 1990 240sx a couple weeks ago and I notice somthing strange. I dont think its normal but I wanted to know if anyone has had this problem before.

when my coolant temp is at normal working temps my temp gauge needle would move down when I acclerate. Does it all the time and its not overheating or anything. I havent had to much time to check it out but Im thinking possible bad temp sensor or cluster?

any clues? Anyone had this problem before?

[smithers584]

how much does it move?

[timlush]

find you coolant temp sending unit(right next to the coolant temp sensor) make sure it is pushed onto the flat prong all the way. i had the same problem when mine was only half way pushed on. i pushed it all the way on and never had the problem again.

[gqxvietboy]

cool.. it'll drop like 1/4 down from the middle. I'll check on that when I have a chance. Thanks

[smithers584]

i think the needle on the gauge is messed up. usually when you temp sensor, the skinny one next to the one that sends your ecu signal, is bad it will make your gauge read either all the way hot or cold. if you want to change it, its like 10 bucks at autozone. i think inertia is playing a little role in this problem with your gauge cluster.

[knate]

i think the needle on the gauge is messed up. usually when you temp sensor, the skinny one next to the one that sends your ecu signal, is bad it will make your gauge read either all the way hot or cold. if you want to change it, its like 10 bucks at autozone. i think inertia is playing a little role in this problem with your gauge cluster.

Are you suggesting that the plastic needle is bending because of inertia? :eek3: Or did you mean to say you think his gauge is messed up? And he told you inertia plays a role in it, he said it only happens when he accelerates.

The reading is resistance based, so if the wire has a poor connection it will definitely change the reading. And it doesn't have to be on/off, a barely connected wire will have a higher resistance than a properly connected wire.

If the needle is jumping between half/quarter when you accelerate, I would say loose wire. Check the small black single-wire plug by the throttle body, there's a good chance there's corrosion or a cracked wire there. If not, you may have to pull your gauge cluster and check the resistance between the cluster and the sensor, should only be a few ohms. I had a similar issue with my 90 when I first got it, was just a crappy connection at the plug.

If your needle moves down slowly while you're accelerating, you could have a thermostat issue and it's reading correctly.

[smithers584]

i was refering to the gauge cluster itself, obviously not the needle bending but that is funny, my bad. but my friends s13 did the same thing, and i believe he put in a jdm gauge cluster and the problem was gone, may have been a US cluster though, cant remember. could be a thermostat problem, but usually they are either stuck wide open or completely shut.

[sultan]

mine sometimes reads correctly at idle, when moving it drops all the way down or jumps all over the place. just get a real temp gauge and ignore it.

[gqxvietboy]

sweet I fixed it. It was loose connection to the temp sensor. Im still missing that U shape metal clip that locks the connectors though so Imma have to go get me a new one.


Thanks guys

[mjjstang]

still should look into getting a better gauge, I was really overheating one day and the only reason i know is becasue I had a gauge. The motor will fry before the stock gauge tells you your overheated.