Gauge Problems
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New User
Joined: Jun 2003
Posts: 8
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From: Montana
Gauge Problems
I have a 1980 Bronco 300 I-6, 4-spd man.
From time to time (actually HALF the time
) My temperature gauge, oil pressure gauge, and fuel gauge will all read "high". It is never just one, but all 3 together. I have asked around, and am having trouble getting a straight answer 
. I know some semi-trucks have a "master sending unit" for all the gauges, but I have been told that this is not the case with my Bronco.
Does anyone know where I should look for the solution?
It's probably an easy fix...I'm just "mechanically challenged".
Thanks.
From time to time (actually HALF the time
) My temperature gauge, oil pressure gauge, and fuel gauge will all read "high". It is never just one, but all 3 together. I have asked around, and am having trouble getting a straight answer . I know some semi-trucks have a "master sending unit" for all the gauges, but I have been told that this is not the case with my Bronco.Does anyone know where I should look for the solution?
It's probably an easy fix...I'm just "mechanically challenged".
Thanks.
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
Gauge Problems
Usually the voltage regulator is OK, it is just a bad ground connection either at the regulator or at the instrument panel itself. When the ground connection opens up the instrument panel voltage will rise to full system voltage (14V) which will overdrive the gages and cause them to read high. Normally the pulsating average voltage for the regulator is 5 volts. It takes an ocilloscope to calculate the average voltage tho.
Senior User
Joined: Mar 2002
Posts: 208
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From: Virginia
Gauge Problems
The Haynes manual for 80 thru 90 F series and Broncos describes a functional test for the insturment voltage regulator in the section on "Water Temperature Sender Testing".
Disconnect the wire to the water temperature sender. (That's the one with one red/white wire)
Connect the lead of a 12 volt test light or the positive lead of a voltmeter the the disconnected wire.
Connect the other lead to a ground on the engine.
Turn the ignition key to on or accessory.
If the light flashes or the needle of the voltmeter fluctuates the insturment voltage regulator should be good.
If it doesn't flicker the regulator is bad.
If no light or no voltage you've got an open circuit.
Not as accurate as an ocilloscope test but usually adequate.
Russ
Disconnect the wire to the water temperature sender. (That's the one with one red/white wire)
Connect the lead of a 12 volt test light or the positive lead of a voltmeter the the disconnected wire.
Connect the other lead to a ground on the engine.
Turn the ignition key to on or accessory.
If the light flashes or the needle of the voltmeter fluctuates the insturment voltage regulator should be good.
If it doesn't flicker the regulator is bad.
If no light or no voltage you've got an open circuit.
Not as accurate as an ocilloscope test but usually adequate.
Russ
Thread Starter
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New User
Joined: Jun 2003
Posts: 8
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From: Montana
Gauge Problems
I posted a question earlier about my gauges all reading "high" (with the exception of the speed-o).
Thanks for all the info...the ground does seem to make the most sense.
Is this ground in an accessible location, or do I have to tear a bunch of stuff apart?
Please pardon my "ignorance"!!
Thanks for all the info...the ground does seem to make the most sense.
Is this ground in an accessible location, or do I have to tear a bunch of stuff apart?
Please pardon my "ignorance"!!
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Joined: Jan 2008
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Gauge Problems
May I ask that you please submit any & all related updates to the original thread?
You may have to look a couple of pages back for it, but FTE & its users would appreciate it.
Pin #9 on the cluster connector should be a black wire & is the ground wire.
You may have to look a couple of pages back for it, but FTE & its users would appreciate it.
Pin #9 on the cluster connector should be a black wire & is the ground wire.
