Temperature gauge 1989 4 ltr. manual

[Keith]

Baffled, temperature gauge does not work, replaced sender in cyl head, no help. Needle stays at bottom, when I push the brake pedal, the needle pegs on the top end, friend told me to check the grounds. Cleaned the one in the left rear tail light, battery to block stud and the cyl head to firewall ground. Nothing helped, same problem.

[ParadiseMJ]

Did you use a thread sealant on the sender?? It grounds (the sender) through the head. If there is enough goop on the threads, it won't ground properly and you'll get a false (or no) reading.

 

...or the gauge itself might be toasted.

 

...or...?

[Pete M]

which temp sensor did you replace? there's a couple or 'em.

[mvusse]

First post states he replaced the one in the head.

[Pete M]

oh right, the computer's one is in the block isn't it. :doh:

[tugalo]

Instrument panel ground is under the drivers side kick panel IIRC.

[Eagle]

Quick test of gauge and wiring:

 

Turn on ignition. You can start the engine, just stay clear of the fan and exhaust manifold. The engine does not have to be running, but the gauges must be energized (i.e. don't turn key to "Accessory").

 

Observe where needle sits. According to you, it should be on cold.

 

Remove the wire from the top of the sender. Do NOT touch it to anything -- isolate it, or you hold it while an assistant reads the gauge. Where is the needle?

 

Now take a probe (or a nail, or screw, or length of stiff wire) and ground the wire directly to the engine (block or head, so big hunk of clean metal).

 

The sender resistance range is 0 - 88 ohms. With the wire removed from the sender, there is no circuit. This is equivalent to infinite resistance. The needle should peg on the hot side. When you ground the wire, the resistance should be close to zero. The needle should be all the way down to the cold side of the scale.

 

If not ... the gauge or the wire to the gauge has a problem.

[Keith]

Eagle: Followed your directions and I apparently have a problem with the wire leading to the gauge, will have to pull the lower dash panel and see if I can locate the problem. Thanks for the information.