85 Bronco Fuel Gauge and Temp Gauge Dead

[jghjunk]

Short version.

Brand new sending unit installed in tank, still no reading with a little over 1/4 tank of gas inside. Have not tried to checkl for grounding issue or ICVR (How do you trouble shoot the ICVR?) Oil Pressure gauge is working well soooooo... I need some direction. Will be chasing wires against the diagram to make sure they are still conducting but could use some go to strategy please!

Jeff

[Gary Lewis]

Easiest thing to do is ground the wire from the sending unit, which should send the gauge to Full in a few seconds. Or put a test light on that wire and it should flicker.

If the oil pressure gauge is working then the ICVR is working. It feeds the oil pressure, coolant temp, and fuel level gauges so if any is working it is.

The output of the ICVR is a chopped DC voltage to a DVM will show all sorts of voltages and isn’t much use. Hence the light.

[jghjunk]

Grounded the yellow wire and fuel gauge went to full. Continuity test to the ground wire to the body showed continuity. What next?

[jghjunk]

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[jghjunk]

I’m getting around 128 to 132 ohms from the sending unit. Could I just have too low of a reading for it to fill up and show a level?

[jghjunk]

OK with more gas in it I’m getting a 68 ohm reading so that tells me it’s working. Does that mean I have a resistance problem somewhere between the sending unit and the gauge?

[jghjunk]

Or do I have the wrong sending unit that’s giving the wrong resistance reading back to the gauge?

[Gary Lewis]

Sorry, have been traveling today.  But you figured it out - you have the wrong sending unit.  The Bullnose senders have ~12 ohms for Full and 72 ohms for Empty.  The later sending units are reversed and have a different range, like 22 ohms for Empty and 120 ohms for Full.

You may have a problem as the sending units and tanks are keyed, with the key on the sending unit and the slot on the tank.  So if the later sending unit fit then you probably have a later tank, or someone cut new slots or cut the key off.

A way around it is to use a MeterMatch, which does allow you to match the sender to the gauge.  I'm running one and it works.

[jghjunk]

You d’A man Gary!  I need the HP10181 Delphi model and that’s not what I bought…

[IowaTom]

<<You d’A man Gary!>>

He really is.  I owe the man a debt of gratitude for this website and his knowledge!  I'd still be scratching my head over getting my '85 back on the road were it not for he and all you guys.

[Gary Lewis]

Shucks, y’all!  You’ll make me  .

Seriously though, we are a community and help each other, a bunch. So I’m thrilled that it is working.