87 bronc.2, gas gauge problem

[brad]

87 bronco 2, 4wd, auto trans, 160K miles. gas gauge readings are very inaccurate, when full reads full, when reads empty still has 13 or more gallons. switched tank/sending unit with known good one, hooked it up first and confirmed it read empty and full, but installed readings wrong as per above. good wiring from gauge to tank. asssuming sending unit ok, problem must be gauge itself? or... i hear of an "internal variable resistor" (IVR), and, there IS a silver, rectanglular, metalic resistor-looking thing on the circuit board of instrument cluster. ford people say they can get one (resistor, replaceable alone), but it's $117.00, and i ain't a gamblin' man! i'd buy it if i knew how to test, but....

so, anybody got a test? IS there a resistor? what most commonly goes out on the gasgauge circuit? is there an aftermarket alternative? anything? thanks!

[miesk5]

from the gang at off-road.com:
"12.1 Why does my Fuel guage behave erratically?
This is a common problem with older Broncos. It can be caused by several things.

If the guage reads normally for some of its range, but reads full or bounces between full and the real value, the most likely cause is a worn level sender. The fuel level sender is a variable resistor located in the gas tank. A wiper attached to the float rides across the resistor, causing a change in the resistance seen by the dashboard guage. A high resistance (or open circuit) reads as "Full" on Ford gas guages. Over time, the wiper may wear through the resistor, causing dead spots which read as full. The only fix for this problem is to replace the sender. On later model vehicles with in-tank fuel pumps, this can be an expensive proposition. Ford only sells the fuel level sender as part of the fuel pump assembly, which can run well over $150.

If the guage behavior doesn't follow any specific pattern, then it is probably related to some other electrical problem. You may want to inspect the wires from the fuel level sender to the guage to see if they are possibly damaged. If other guages are also erratic, there is a good chance that the dashboard voltage regulator is bad.

http://web.archive.org/web/200111220.../bbfaq.html#12
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by bronco1;
"Disconnect the connector at the fuel tank,ground the yellow with white tracer wire(make sure you have a good ground),turn the key on-if the gauge goes to empty,chances are,the fuel sender is the problem.If the gauge doesn't move,then recheck the grounding of the y/wt wire,if it is good then the problem is is forward of the sender(wiring/connectors/instrument cluster)."
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by Steve84
"Remove the cluster & clean the terminals on the connectors and on the film circuit"
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Since this was written, some suppliers do have the sender as a seperate item.

Spectra Premium Industries gas tanks, & fuel sending units
FG38B (SENDER; W/O FUEL PUMP)
http://www.spectrapremium.com/produc...utomotive.html
FG38B (SENDER; W/O FUEL PUMP)
1987 FORD BRONCO II 1106165
Eng. Fuel Fuel Type Aspiration VIN Eng Desg.
V6 - 177 (2.9L) GAS FI N T
----------]
http://www.flotamex.com/CatalogFord.htm

etc.

[scuba_steve34]

LMC Truck Parts - Pages 110 and 111

without fuel pump 63.00 237.00 with fuel pump