I have a 1967 Mustang, 289 Convertible on which the gauges all have suddenly
become pegged hard over as soon as I turn on the ignition.
I have replace the voltage regulator, and still get the same results. With
the voltage reg disconnected, I still get the same results.
Every thing works except not knowing haw much gas, or what the temp is, etc.
Any suggestions on where else to trouble shoot would be appreciated.
Thanks
Matt
Jan - 06 Sep 2007 04:24 GMT
> I have a 1967 Mustang, 289 Convertible on which the gauges all have suddenly
> become pegged hard over as soon as I turn on the ignition.
[quoted text clipped - 9 lines]
>
> Matt
Ground connection(s) to the gauges?
Jan
ataylor142@comcast.net - 15 Sep 2007 15:51 GMT
> I have a 1967 Mustang, 289 Convertible on which the gauges all have suddenly
> become pegged hard over as soon as I turn on the ignition.
[quoted text clipped - 9 lines]
>
> Matt
I would think if the ground to the gauges was bad the dash lights
would also be dimmer or off.
I guess that the voltage regulator mounted on the back of the dash
cluster is bad.
Rich
Ashton Crusher - 15 Sep 2007 21:24 GMT
>> I have a 1967 Mustang, 289 Convertible on which the gauges all have suddenly
>> become pegged hard over as soon as I turn on the ignition.
[quoted text clipped - 15 lines]
>I guess that the voltage regulator mounted on the back of the dash
>cluster is bad.
The OP said he replaced it.
Eugene L. Kimball - 16 Sep 2007 10:54 GMT
>>> I have a 1967 Mustang, 289 Convertible on which the gauges all have
>>> suddenly
[quoted text clipped - 20 lines]
>
> The OP said he replaced it.
For what it's worth.
The original gauges are insulated from ground by a small strip of fiber
material with two holes for the electrical terminals. If a gauge is loose,
or not properly mounted, and one of the terminals makes contact with the
instrument gauge housing you will cause a short and blow your 5 volt voltage
regulator. If you replace the voltage regulator without fixing the problem
you'll just blow the new one too.
If you still have the problem I would suggest replacing the mechanical 5
volt regulator with a solid state one.
It can get expensive trying to trouble shoot by the replacing the voltage
regulator, as the mechanical ones cost 30 or 40 dollars where as the solid
state cost about two dollars. You can find the modification instructions on
the internet and you can buy the part required ( Solid State Voltage
Regulator LM7805 ) at any Radio Shack.
ataylor142@comcast.net - 16 Sep 2007 11:34 GMT
Yes, but if power flows thru the voltage regulator then to the gauge
then tthru the sensor to groung, why would the gauge still peg, if he
disconnected it? I assumed he meant the voltage regulator under the
hood....
Matt please let us know what you find out.
Rich
Eugene L. Kimball - 16 Sep 2007 13:15 GMT
> Yes, but if power flows thru the voltage regulator then to the gauge
> then tthru the sensor to groung, why would the gauge still peg, if he
[quoted text clipped - 3 lines]
> Matt please let us know what you find out.
> Rich
I'm not an electrical expert but I think the voltage regulator under the
hood controls the voltage coming from the alternator to the battery. The 12
volts required to run the car actually is supplied by the battery. The
alternator function is to keep the battery charged and the, voltage
regulator under the hood, just controls that charge. For example, a bad
voltage regulator can cause a battery to be over charge and eventually the
battery will die but the car will still run until it does.
The instrument panel 5 volt voltage regulator, regulates the 12 volts coming
from the battery to the oil, gas and temperature gauges. It does this by
means of Bi-metallic Arm with a heating coil wrapped around it and as the
current flows through the coil it causes the arm to bend and separates the
contacts on the end of the arm. When the arm cools it relaxes and bends back
making contact with ground again and the cycle repeats itself. If you have a
short in your 5 volt circuit it can cause the coil or the Bi-metallic Arm to
draw to much current and they can melt or break and when this happens if
the upper arm is in contact or fused to the lower arm your gauges will be
pegged.
Hope this makes sense!
64chevy - 22 Sep 2007 19:41 GMT
>> Yes, but if power flows thru the voltage regulator then to the gauge
>> then tthru the sensor to groung, why would the gauge still peg, if he
[quoted text clipped - 22 lines]
>
>Hope this makes sense!
have you tried reversing the leads on the back of the instrument cluster my
65 had that problem
Spike - 23 Sep 2007 03:51 GMT
>I have a 1967 Mustang, 289 Convertible on which the gauges all have suddenly
>become pegged hard over as soon as I turn on the ignition.
[quoted text clipped - 9 lines]
>
>Matt
According to Mustang Monthly, the most likely cause of pegging is the
regulator on the back of the instrument panel. Not the only possible,
but the most common. Could it be that somehow you are unknowingly
frying the replacement regulator?