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Problem with temp gauge

Trail Ready

NAXJA Forum User
Location
Cerritos ca
My temp gauge is going crazy.It will read accuratly and then the needle will just fall all the way to the left like if the engine in cold.After driving it a little more the needle pops back up to *210 an then falls back down to cold again wtf???Is the thermostat going bad?I did put a new radiator in it about 200 miles ago it never acted up before I did that.What do you think??:compwork:
 
what year? sometimes the wire gets worked loose in the little sender and will do that. make sure the connection is good.
 
check the wires to the sensor, check the grounds on the engine block as that sensor needs a good ground to read correctly, and post the year of the jeep, it will help us diagnose the problem better. if it's a pre 97 HO there is a sensor in the back of the head and one in the t-stat housing, the one at the back of the head is what sends the signal to the gauge.
 
On 96-down the gauge is fed by a dedicated sender. It's a little one-wire thing at the back of the head on the driver's side. Your 94 it should have a little white rectangular connector. That connector is probably loose.

The way gauges typically work is that current flows through a circuit and a sensor or sender varies the resistance. Meanwhile the gauge itself passes the current through a miniature coil, which creates a magnetic field. As resistance goes down the magnetic field increases in strength and pulls the gauge up, and conversely when current goes down the gauge drops. You can test this with ignition on by disconnecting the sender and gauge will go to zero, or ground it to a bolt and gauge will peg to max.

Since your gauge is periodically dropping low you probably just have bad connection.

It's also possible that the ground straps are dirty or corroded and need cleaning. There is a braided steel wire at the back of the head that grounds the engine to the body, which should be disconnected and cleaned with wire brush and sandpaper periodically.
 
it sometimes happened to me, but it did't reach to the max temperature , it just went down and return to the normal position, check de conection of the sensor, mine had a bad wire just before the harness.
 
ok I found it.The plastic part broke.What does that part cost and where can I get it locally?

dsc08654o.jpg


here is de sensor, you can disconnecting from the sensor, the cable of the harness was broke, and I just connecting very well.
 
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