66 mustang constant voltage regulator

Hope one of you experts can help me with this one.
I have been having some strange behaviour from the gas gauge in my 66.
No surpirse there I know. When I got the car the gauge was dead the
whole time. I replaced the sending unit which is sending fine (checked
variation in resistance) but still no change. Changed the constant
voltage regulator exactly as it was previously mounted on the back on
the instrument panel - attached to the metallic back plate of the
instrument panel via a small screw. This made no difference either
despite there being 1/2 - 3/4 of a tank of gas in there. All other
gauges seem to be fine.

Now here is the strange thing. Last night I was looking at it again and
noticed that if the constant voltage regulator is NOT screwed into the
back plate of the instrument panel, i.e insulated from it, then the gas
gauge springs to life. Unfortunately the TEMP and OIL gauges then max
out constantly. Also on the screw that attaches the regulator to the
back plate there is a male tag and a black wire running from it that
has been cut by the previous owner - looks like it has been connected
somewhere - maybe an earth ????

Can anyone please tell me exactly how the regulator must be installed
for correct performance and what this black wire is there for because
it is driving me mad???

many thanks.

Jonathan

"JB" > wrote
> Now here is the strange thing. Last night I was looking at it again and
> noticed that if the constant voltage regulator is NOT screwed into the
> back plate of the instrument panel, i.e insulated from it, then the gas
> gauge springs to life. Unfortunately the TEMP and OIL gauges then max
> out constantly. Also on the screw that attaches the regulator to the
> back plate there is a male tag and a black wire running from it that
> has been cut by the previous owner - looks like it has been connected
> somewhere - maybe an earth ????

You might check into solid state regulators. They are now being produced and
should negate this issue entirely.
--
Scott W.
'68 Ranchero 500 302
'69 Mustang Sportsroof 351W
ThunderSnake #57
http://home.comcast.net/~vanguard92/

Here is a photo of the instrument cluster voltage regulator:
http://www.rockauto.com/ref/Airtex/D...tml?1V1004.jpg

My '67 Lincoln repair manual shows an identical looking voltage
regulator in the instrument panel wiring schematics. It shows only two
wires going into the regulator. One wire from the fuel gauge and one
wire that connects to the ignition switch. The body or metal case of
the instrument cluster voltage regulator is not shown to be a part of
any circuit. It does not show it connected to ground or anything else.


The manual says test the instrument cluster voltage regulator by "check
for voltage at the fuel gauge feed wire (black with green stripe) at
the fuel gauge. The voltage should oscilate between zero and about 10
volts. If it does not, the instrument voltage regulator is defective,
the radio suppression choke is defective, or there is a short to ground
between the voltage regulator and the fuel gauge."

I am guessing "radio suppression choke" means a noise suppression
condenser on the distributor or somewhere.

Good luck. If you really want to go nuts, buy a '67 Lincoln. The
power steering pump also runs the windshield wipers.

JB wrote:
> Hope one of you experts can help me with this one.
> I have been having some strange behaviour from the gas gauge in my 66.
> No surpirse there I know. When I got the car the gauge was dead the
> whole time. I replaced the sending unit which is sending fine (checked
> variation in resistance) but still no change. Changed the constant
> voltage regulator exactly as it was previously mounted on the back on
> the instrument panel - attached to the metallic back plate of the
> instrument panel via a small screw. This made no difference either
> despite there being 1/2 - 3/4 of a tank of gas in there. All other
> gauges seem to be fine.
>
> Now here is the strange thing. Last night I was looking at it again and
> noticed that if the constant voltage regulator is NOT screwed into the
> back plate of the instrument panel, i.e insulated from it, then the gas
> gauge springs to life. Unfortunately the TEMP and OIL gauges then max
> out constantly. Also on the screw that attaches the regulator to the
> back plate there is a male tag and a black wire running from it that
> has been cut by the previous owner - looks like it has been connected
> somewhere - maybe an earth ????
>
> Can anyone please tell me exactly how the regulator must be installed
> for correct performance and what this black wire is there for because
> it is driving me mad???
>
> many thanks.
>
> Jonathan