LH LX FUEL TANK SENDER UNIT

Thanks for that

What do you mean 'ac set to 20'? I take it AC on your meter is for Alternating Current. Motor vehicle electrics run on DC - Direct Current.

Your multimeter should have a 0 Ohms setting. 200 Ohms is too high, the sender unit operates in the range of 10 to 73 Ohms.

Only way to test the sender properly is to remove from the tank and set it up on the bench.

Edited by S pack, 16 June 2019 - 04:16 PM.

thanks. will check.

i think i meant dc as in direct current. that's about the extent of my electrical knowledge and i still got it wrong when trying to explain! it has a range of values available. the AC has only 2.

ohms lowest is 200 I think.

I got the feeling i broke it twice somehow! as it used to work now both seem broke. 

was hoping to avoid another removal/refit but maybe not.

Maybe post a pic of your muliti-meter. We can try to help from there. if you mean your meter is set to the 200 ohm RANGE then that's OK. But a reading of 200 ohms means sender is faulty.

I would say that in fixing the leak you have may have somehow insulated the senders connection to earth. Go to Jaycar and buy 3 resistors (the white square ceramic ones) about 20 cents each. Get a 10 ohm, a 70 ohm and a 40 ohm one or as near as those values that you can get. Each resistor will simulate the empty, mid and full ranges on your gauge. disconnect the wire off the sender unit at your tank and place one of the resistors between the wire and a good earth. with the ignition switched back on the gauge should read. Even better take out the sender then attach a ground wire to the sender metal body and while moving the sender arm up and down the gauge should move. Be patient as it takes a minute or so to move and settle.

I would say that in fixing the leak you have may have somehow insulated the senders connection to earth. Go to Jaycar and buy 3 resistors (the white square ceramic ones) about 20 cents each. Get a 10 ohm, a 70 ohm and a 40 ohm one or as near as those values that you can get. Each resistor will simulate the empty, mid and full ranges on your gauge. disconnect the wire off the sender unit at your tank and place one of the resistors between the wire and a good earth. with the ignition switched back on the gauge should read. Even better take out the sender then attach a ground wire to the sender metal body and while moving the sender arm up and down the gauge should move. Be patient as it takes a minute or so to move and settle.

Very good point. It does sound like an explanation. I did squish the inside rubber o ring down hard with pliers to try close the seal. if it was too far gone as it was leaking as was the big one that got replaces it could have easily made an earth.

Having no clue about why it's there and electrics I wouldn't have known any better.

All proving what i already knew- my skills/knowledge in the electrical dept is embarrassing!

Should the other side - the connector that goes along the wire to the dash be jumping around like that 0.XX-6.XX when tested with alternate current set to 20, red in the plug hole, black on the car body?

I wouldn't bother with the meter if you don't know what you are doing other than to test for voltage. Just pull off the connection at the sender unit as I suggested and try the resistors. Whatever you do don't just touch the wire straight onto earth as you need the resistance in the circuit and you run the risk of damaging the gauge.

If you're using a digital multimeter it will jump around as you say.

Best for checking low impedance items like the sender is an analogue multimeter (old school) as they're more stable.

There's no point in testing the gauge's impedance, that won't tell you much.

The fuel tank sender probably needs a good strip and clean, and calibration, as the grounding within the sender becomes intermittent with age.  Sometimes they need a new internal resistor.

I've refurbished heaps of them.

If you're using a digital multimeter it will jump around as you say.

 

Best for checking low impedance items like the sender is an analogue multimeter (old school) as they're more stable.

 

There's no point in testing the gauge's impedance, that won't tell you much.

 

The fuel tank sender probably needs a good strip and clean, and calibration, as the grounding within the sender becomes intermittent with age.  Sometimes they need a new internal resistor.

 

I've refurbished heaps of them.

yes,mulitmeter is the cheapest digital one from altronics that the helpful sales assistant showed me how to use for the 2 tests i thought would be useful.