yo 90,
What year Bronco is this happening in? your 86 ot 90?
78-86 has the old sender, 75 Ohms Empty & 10 Ohms full;
87+ has new, 16 Ohms Empty & 158 Ohms Full..."
Source: by Aikidoka
Instrument Voltage Regulator (IVR) in 78-
86; "...The IVR can fail two different ways. it will quit working altogether, thus none of the gauges will work. O
r two, it will stick, and the gauges will peg to the extreme right, then it will unstick and fall back to normal. The IVR is a pulse type. The voltage is regulated by how fast the pulses are. When it sticks, it doesn't pulse, etc... Try tapping on it. Make sure the cluster ground is in good shape. If the IVR isn't grounded or has an intermittant ground, it wont pulse like it should either. Rebuild it, see
http://www.turbocoupe.org/techinfo/ivr/IVR.htmold or,Suggest getting one from a Yard; Since there are about 12 different types, make sure to take the old one with you; Fits: 1971/86 F100/350; 1971/91 Econoline; 1978/86 Bronco; 1977/79 LTD II/Ranchero/Cougar/Thunderbird without Tachometer; 1972/76 Thunderbird/Continental Mark IV; 1971/72 LTD/Mercury Marquis for MOTORCRAFT Part # GR513 (D1AF10804AA, D1AZ10804A)..."
Source: by miesk5
For now;
Fuel Level;
Testing & Connector Pin-Outs in 92-96 Bronco (87-96 F-series & Bronco similar);
Sender Range: 16 Ohms Empty; 160 Ohms Full; "... gauge that pegs past full indicates an open circuit (broken wire; unplugged connector; corroded terminal; burned sender) on the Y/W wire.
gauge that pegs past empty indicates a short to ground (pinched to the frame, body, or dash supports) on the Y/W wire, OR a sunk float.
gauge anywhere in between that doesn't move indicates an open circuit (blown fuse; corroded terminal) on the power (battery) side of the gauge OR a bad instrument cluster ground at C251 pin 9.
The terminals of C251 (& C250) are known to corrode & lose contact. Polish both the connector pins AND the film circuit pads with brown paper or a pink eraser.
The larger version of C441(WPT454) was used until 93. The level sender can usually be disassembled & repaired by bending the wiper arm inside the plastic housing to apply slightly more force..."
Source: by Steve @
http://www.supermotors.net/registry/media/744437_1
see connector pin-out diagrams and more info in his site
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Testing in an 87; "Here is a way to check the calibration of the gauge: With the connector off and key on, a 22 ohm resistor between the two leads should give it a mid scale reading, a 73 ohm resistor should put the needle on E, and a 10 ohm resistor should put the needle on F. To check the gauge, check the resistance across the gauge, it should be between 10 and 14 ohms. Also check the voltage across the connector, it should read 5 volts. Bad connections, and grounds can also be a problem, especially the engine to body and engine to frame ground. Clean the connections for the battery to engine and frame grounds, clean the connection from the intake manifold (driver side) to the fire wall..."
Source: by Seabronc (Rosie, Fred W) at Ford Bronco Zone Forums
Testing; "...the little resistive strip in them gets bad and causes erratic readings. Also, while you are at replacing it, check out the connector to make sure the ground is good back to the battery. Do a resistance check from the black lead to the battery (-) post. If is is more than a couple of ohms, run a new ground lead to it. Those resistor values were from an 80-86 shop manual, for checking the gauge and circuit..."
Source: by Seabronc (Rosie, Fred W) at Ford Bronco Zone Forums
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Engine Coolant Temperature & Sender
Testing in a 90; Pull the RED/White wire off the sender & ground it to the block, intake, or head. Then turn the key to RUN. If the needle pegs, replace the sender. If not, diagnose the circuit. Wiring Diagram in a 90 for Gas Engines w/Tachometer & Diesel Engines by SeattleFSB (Seattle FSB); Pull connector from sending unit and test for Ohms at sender with engine cold; 74 ohms and with engine at normal operating temp; 9.7 ohms; check ground; G100 LH side of Radiator support G101 RH side of Radiator support G102 RH side of Radiator support G103 LH rear side of engine, near knock sensor G104 LH rear side of engine compartment, near electronic engine control (EEC) module, on the left fender close to the firewall G105 LH Side of engine G106 RH fender apron, near voltage regulator G107 RH fender apron, at starter relay G108 RH fender apron, at voltage regulator G109 RH fender apron G201 LH rear side of I/P (looking at the diagram it is at the bottom of the driver's side dash assembly. Screwed to the bottom edge, just to the left of the steering column. It is the ground for the instrument cluster) MIESK5 Note; G201 also serves tailgate window motor; G202 Behind RH cowl panel G203 RH rear side of radiator support G204 On steering column G205 Behind Center of I/P (Dash), near speed control amplifier G400 LH side of cargo area, near rear light assembly G401 Below LH side of cargo area, near crossmember G500 Inside driver's door, near left door speaker Locations in a 90 from 1990 Bronco EVTM; G201 LH rear side of I/P (looking at the diagram it is at the bottom of the driver's side dash assembly. Screwed to the bottom edge, just to the left of the steering column. It is the ground for the instrument cluster) MIESK5 Note; G201 also serves tailgate window motor. So if that works, iggie it.
by miesk5 at
http://broncozone.com/topic/23573-pulled-codes/
Testing; "...Pull the R/Wh wire straight off the sender & ground it to the block, intake, or head. Then turn the key to RUN. If the needle pegs, replace the sender. If not, diagnose the circuit. Also, read this caption: TSB 95-13-02 Erratic Temperature Sender - Factory temperature senders with a date code before 2774 are known to be defective. The code is stamped into the side of the hex. The format is the Julian date + the last digit of the year, so that's the 277th day of 1994. So 0085 is good; 1934 is bad; 3034 is good; 2765 is good; 3582 is bad. The sender should test at 74 Ohms cold; 9.7 Ohms hot. If you're having trouble with your temp gauge, try to read the date off the sender before any other diagnosis. A new sender from NAPA is under $10..."
Source: by Steve83 (Steve, That dirty old truck) at Ford Bronco Zone Forums
http://broncozone.com/topic/18824-coolant-gauge-inop/
Wiring Diagram in an 86
Source: by Xris at
http://www.supermotors.net/registry/media/648662
Wiring Diagram in a 90 for Gas Engines w/Tachometer & Diesel Engines
Source: by SeattleFSB (Seattle FSB) at
http://www.supermotors.net/registry/media/928136
