Fuel and Temp gauge issues
You need to start by checking the gauges "in operation" with known resistances to simulate senders. Since you have an extra? fuel sender you can set that for desired resistance and then check the gauges. Both gauges should act the same with same sender resistance
Here is a photoshopped tester someone added in the resistances
Make sure you are getting full battery voltage to IVR, and check carefully the resistance and condition of the IVR contact fingers to the board traces. Several of us have had to solder jumpers from the contact fingers to the traces.
Suspect connection problems at the gauge studs/ nuts. Loosen/ tighten them a few times to 'scrub' the connection.
It is always possible the IVR or gauges are defective
And make certain the harness connector pins are in good contact with board traces. Best to clean and solder all of them, or ate least check carefully for "loose"
You need to start by checking the gauges "in operation" with known resistances to simulate senders. Since you have an extra? fuel sender you can set that for desired resistance and then check the gauges. Both gauges should act the same with same sender resistance
Here is a photoshopped tester someone added in the resistances
Make sure you are getting full battery voltage to IVR, and check carefully the resistance and condition of the IVR contact fingers to the board traces. Several of us have had to solder jumpers from the contact fingers to the traces.
Suspect connection problems at the gauge studs/ nuts. Loosen/ tighten them a few times to 'scrub' the connection.
It is always possible the IVR or gauges are defective
And make certain the harness connector pins are in good contact with board traces. Best to clean and solder all of them, or ate least check carefully for "loose"