lwg8tr0514

New Classics industries gauges installed during restoration. Fuel gauge was not operating and looked and sending unit on bottom of tank was bad. Replaced unit and connected wires and tank float even up to top still maxes out gauge at 1/4 fill . Myself and two good corvette mechanics are at a loss. They did not test the resistance on the float assembly before install. Anyone else have this problem?

Vega$Vette

C1 or C2? And what gauges from Classic Industries?

lwg8tr0514

c2- 1964

Vega$Vette

And what gauges from Classic Industries?

lwg8tr0514

https://www.corvettecentral.com/c2-6...-gauge-lens%2f

Vega$Vette

OK. Those are Classic Instruments Not Classic Industries.

I would check to make sure you have good grounds at the gauge and conform the fuel tank is grounded.

lwg8tr0514

Yep both were checked. Good grounds and the other gauges work well.

Vega$Vette

Guess would be bad sending unit out of the box.

lwg8tr0514

Yea, my thought also. The sending unit not sending the right resistance to gauge. Annoying as hell, these Chinese-made parts. Why to not be afraid of them taking over the world, half their military stuff would not work. :-)

65GGvert

Disconnect the tan wire from the sending unit with key off, and measure resistance from the connection lug of tan wire you pulled off to ground. Not the wire side, the connector you pulled the tan wire from. What ohms reading? Now move red meter lead to other wire connector (can leave connected). It should read 90 ohms to ground.

lwg8tr0514

I'll try that, thanks!

lwg8tr0514

"Now move red meter lead to other wire connector (can leave connected). It should read 90 ohms to ground"
Sorry a little confused, red lead to what connector?

65GGvert

The ohm meter lead (you have a red and a black, black connected to ground), move that red lead to the pink wire connector at the sender. Reading from the pink wire connector on the sender to ground with the meter should read about 90 ohms.
If you want to check the sweep of the gauge, disconnect only the tan wire from the sender and turn key on, gauge should move to full.

Let's see if I can sum up better. With all leads at sender disconnected, you should read 90 ohms from where pink wire came off to ground. The resistance reading on the connection the tan wire came off varies with float position (how much gas in tank). Full tank should read 90 ohms, empty tank should read single digit ohms.
Tell me if you are not familiar with using an ohm meter and we can try another way.

lwg8tr0514

No I'm familiar with testing resistance. So to paraphrase, disconnect and test where I removed the pink wire at the sender to ground and should read full 90ohms?

Factoid

Did the fuel sender come with the gauge package? The reason I ask is the C2 Corvette uses a weird powered sender and these gauges are not compatible with the oem sender without some minor rewiring.

65GGvert

Yes and tan wire post varies with float

2KREDVert

Not a problem for them. They keep the good parts and send the junk to us!

65GGvert

True, a non C2 gauge could cause a good sender to not match. Did you get a stock style sender replacement?

Vega$Vette

I believe the gauge package from Classic Instruments comes with the 90 ohm Sender that works with the gauge as opposed to the standard style C2 Sender

lwg8tr0514

Yes a 0-90 ohm stock one. One thing with the fuel gauge, their wiring recommendation different than stock. You do not use the pink/black wire. You just hookup black where pink/black was and brown on larger post. The ground spade you put nothing on