Oil Level Float Testing

[l_turn9]

Hi Gang,
My oil level gauge stopped working and I m checking the Float mechanism in the oil tank. I put a jumper between the two electrical connections and saw nothing change on the gauge on the dash. so i am wondering what test I should do next? I am thinking about testing for continuity between the 2 electrical posts on the float. Even at it's lowest level I think there should be some continuity - it's basically a rheostat like the ones I used on slot cars growing up in the 60s. Any other tests I can run before I trash this one and buy another? I'd like to confirm this is the problem before buying another...

[patz]

Pull the float, could be corroded or something that a visual may help to diagnose. Easy to replace and not to expensive....or you could ignore it and just use the dip stick.

[ischmitz]

Think about it. I'm assuming the dash instrument is registering nothing. So either the sending unit failed OPEN or else:

If the sending unit failed open and you "replace" it by using a jumper wire in the needle should go all the way up with the ignition ON. If not there is something wrong with the wiring to the sending unit. One wire is GND and the other runs to the instrument itself. If you short these the needle must move.

The sending unit is just a variable resistor as you said.

Ingo

[Tom Elder]

My gage has not worked since I bought the car. I put LED gauge lights in this past winter and discovered a wire was not plugged in. Works fine now.

[lsf911]

I_turn9,

When I purchased my car the gauge didn't work at all. First thing I did was remove the sender from the oil tank, jumper one connection to car ground and the other directly to the gauge connection itself. With the key in the on position, move the sender lever up and down and watch the gauge oil level move along with it. If no movement, one of them is definitely bad. If there is movement then your wiring is bad. If the wiring proves good, putting a meter on the 2 connections of the sender should vary the resistance when moving the arm up and down. If that happens then it's your gauge.

[l_turn9]

Thanks guys! You were very helpful in helping me visualize what the gauge is doing. BTW, today when I started the car I watched closely to see what the gauge did as I cranked the engine. At the very 1st instant of me cranking the ignition I saw the needle jump up about 1/4" then it settled back down and stayed there.

Tom - do you recall where the disconnected wire was that you found was located?

Ingo - does the fact the gauge jumps when the ignition is 1st cranked change your comments?

Thanks again -

[Tom Elder]

It was just not plugged into the back of the gage. I should have checked that years ago. When I got the car, fan and wiper motor wires were disconnected as well.

[ischmitz]

L_tuern9,

the common failure for these units is the wire wearing through and thus they fail open. I can't say why you saw nothing when you put the jumper in place. I would expect the needle to have moved.

To further test I'd go from the instrument out. All tests with the ignition in ON:

- Connect the input from the level gauge to GND and see if the needle moves up
- Measure the voltage on the input pin of the level gauge with ignition on. There should be some close to 12V.
- Then connect the wire back to the gauge, disconnect it at the sending unit and measure the same voltage. If not the wire is interrupted somewhere. When measuring connect the other lead of the voltmeter to the chassis or wheel lug
- Then measure the voltage by connecting the other lead of the voltmeter to the other connector near the sending unit - should still be the same.
- Finally touch the two connectors 0 - the needs to move\

As an alternative you can remove the sending unit and inspect it with a magnifying glass. The worn area will become apparent. You can even solder the constantan wire back together (worked for me) as a temporary fix.

Let us know what you find,
Ingo