Oil Level Gauge Barely Moves

l_turn9 · l_turn9's Garage

My Oil Level Gauge stopped working a year + ago and today I did some troubleshooting. I disconnected both wires at the Float/Sender and set my DMM set to 'DC V's'. The DMM probes were attached to the loose wires from the Gauge, and it reads 7.6v.

My battery reads 12.4v (I keep it charged with a float charger). I then attached the Red wire from the Gauge back to the center post on the Float Assy, leaving the White Wire unconnected to the grounding Stud. I turned the Ign. Sw. on but I am still getting no movement in the Gauge Needle. Based on other postings, I think that's what I was supposed to do; and if that is correct, I would have seen the needle peg to the full up position in the Gauge, right?

At this point, I am planning to remove the Float Assy, and see what the rheostat looks like & test it more; does that seem like a reasonable direction to go next?

TIA --

darrin · 12-04-2020, 06:14 AM

The sender creates resistance (lowers voltage) when the float's down (low oil) and the resistance decreases as the float rises (increases voltage) -- to check the gauge, connect the two wires at the float together (no resistance) and the gauge should peg full. If this occurs, the issue's with the float assembly -- still no movement, look elsewhere

l_turn9 · l_turn9's Garage

Thank you - very clear instructions! I'll try & let you know -
Larry

l_turn9 · l_turn9's Garage

Hi Darrin,
I tried what you suggested - it worked perfectly! It pegged, so I know I need to check out the Sender/Float Assy. From the directions elsewhere on the Forum, it tells how to repair the metal bands and all the other parts. I'm pretty confident I will be able to fix it. I'm a little slow when it comes to electrical stuff, but I do pretty well with mechanical stuff. I'll try to remember to take some photos showing what I did and how I did it. I do need to remember to order a gasket though...
Thanks again!

darrin · 09:05 AM

Good to hear !

Now that you've confirmed the circuit's good, you might want to make sure the oil level sender tabs themselves are clean and corrosion free before removing the oil level sender -- If you end up needing to remove the sender, believe you'll need to get a replacement oil tank/sender gasket when it comes time to reinstall the sender.

Walt Fricke · 12-04-2020, 10:00 PM

I am dubious that the rheostat for this sender can be repaired. The failures I have seen have been due to wear on the wire windings where the sliding part contacts them. I don't think you could solder such a break back together.

If you are a ham, maybe you might think to rewind the rheostat part? Take it as a challenge? Replacing the unit is the more common approach.

Now if there is some mechanical issue with the float and lever stuff, maybe that could be fixed.

l_turn9 · l_turn9's Garage

Thanks Guys! 1st, the connections - both were tight and clean. re Fixing the windings - I may play with soldering it as I wait for my new one to arrive but my expectation for successfully repairing the broken wire is low. BTW, It seems these Level Senders don't have a great lifespan - it's a pretty simple circuit but this is the 2nd I have had fail. But if I can fix this one, I'll have a spare..

Sailkane · Sailkane's Garage

My experience....went through the same process with my car. After removing the sensor, hooked up the wires and moved the sensor up and down...everything worked.

On my car after initial start up gauge moves but barely. After driving around needle stays the same.
After stopping and at idle the gauge moves to normal oil level position ( due to the oil thermostat opening and the oil flowing).
Never really stays in the normal position during driving.

l_turn9 · l_turn9's Garage

Thanks for that info - What do you think caused your sending unit to malfunction, was it something unknown that was fixed when you removed it ? FYI - I also connected my DMM but mine shows there is no continuity between one side of the rheostat and the other side of it.
BTW, Has anyone tried the URO brand of OL Sending unit? I am curious if the length of the rod with the float on it is the same as the OE sending units.

Walt Fricke · 12-05-2020, 03:50 PM

Lturn - be sure to let us know what the fault you find was, and if you fixed it, how. It is a common issue.

The first one I removed had worn the resistance wire through. The second one worked for a while, but started getting erratic. That may have been due to bad connections, but fiddling with them didn't seem to stop this so despite the fact that the new one had two orders of magnitude fewer hours on it I just disconnected the gauge and did without. This is a race car, so I'm not glancing at it as I drive anyway.