1968 Barracuda 383/4spd

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vesparex

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I have an oil pressure indication issue.
Mechanical test confirms oil pressure. Done.
Ground grey wire unhooked from sender and turn key on, gauge sweeps smoothly to high then fluctuates, I assume the fluctuation means that the voltage reg is working.
Multimeter at terminal end, key on, unhooked from sender, moves to 4-5v, again, fluctuating.
Sender (for dash gauge, not idiot light) grounds fine to the engine and body with a continuity test.
Sender (new) ohms test shows 19-22 at idle.
But put it all together and dash gauge doesn't move. All other gauges operate, temp, fuel and amp. All operating.
What am I missing?
 
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Line 3 if you unhook the wire and the gauge moves, you have a volt bleed somewhere. Do you have a 68 service manual?
 
[QUOTE="jaws, post: 1973220409, member: 3343"[ Do you have a 68 service manual?[/QUOTE]

No, I do not.

Duane
 
Get you a FSM, they can be downloaded for free on several sites.
 
The temp gauge and the fuel gauge are both powered up by the same dash-gauge regulator. That regulator is just an on/ off switch with a heater in it. When powered up, all it does is continuously turn on and off, in a duty cycle that accomplishes an average of about 5 volts. The factory gauges are so slow that they rarely catch the fluctuating.
Of course the oil-pressure sender has to vary it's ground resistance with changes in oil pressure, to make the gauge work...
 
Line 3 if you unhook the wire and the gauge moves, you have a volt bleed somewhere. Do you have a 68 service manual?
I found a 1967 FSM for A Bodies this weekend and read through the cluster/gauge portion, repair and trouble shoot portion. Did not see anything about how to check for voltage bleed.
Can someone give me a little insight?

D
 
Put an analog ohmmeter across your oil pressure sender to ground. Take a reading with engine off, then watch the needle and start up the engine; the needle must swing . And must not go to open-circuit, nor to full continuity. The actual numbers are less important than, than the actual swing.
 
sender with oil pressure shows 19 to 22 ohms. that should move the needle to about middle of range/gauge screen. Shorting the wire to the block is zero ohms test. That can make a faulty gauge do what normal the 80-10 ohm signal would not. Zero ohms should take the needle to its max position and hold it there. A fluctuation is not normal. The beam should not heat and cool fast enough to fluctuate the needle if the limiter is working properly.
What I would do... short the temp sender wire to the block. If this needle fluctuates also, the limiter output is the problem.
Your fuel gauge has a slither of metal on its backside that sits on a unpainted spot in the housing. This provide ground path for the limiter. A few owners have found a poor contact here to be the problem.
 
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