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[ludwig]

Hello,
I have a 1964 TR4, Bone stock accept that its been converted from posative ground to negative. The fuel guage and temperature gauge both read roughly 30-40% higher than actual. Is this likely to be a grounding issue or ??

Thanks DK

[charley fitch]

Or possibly a problem with the voltage stabilizer.  I understnad that the dash instruments operate at 10 volts and your system operates at 12 or more volts.  It clould be that the stabilizer is the problem.  The stabilizer is found under the dash on the passenger side all of the way to the front of the foot well and up in the right hand corner.  I'm no electronic wiz so I can not tell you how to check the unit.  Likely some one else can help from here.
Charley Fitch

[vila]

First, I have a question. Did you replace the original generator with an alternator?  I ask this because it is my understanding that it is possible to use the original generator and by reversing the battery and changing the polarity of the generator you can change the car into a negative ground system and the only other thing that needs to be done is to reverse the connections on the AMP guage.  I don't believe the voltage would change by only reversing the generator polarity.

Charley could be correct with the voltage stabilizer, but I have no idea how they function.

If you changed to an alternator, you may be putting out more volts than the original generator, but don't quote me on that.  Most modern alternators put out somewhere around 14.2 volts to keep the 12 volt battery fully changed and I am not sure how voltage stabilizers may handle higher voltage.   

I had a similar problem with the gas guage on my 1933 Chevrolet when I put an 8 volt battery in to replace the original 6 volt battery.  I kept the original generator, but I had the ability of increasing the output which keeps the 8 volt battery fully charged.  The Fuel guage was out of calibration and I just live with it.  No problem with anything else on that car, since the temp guage is a capillary tube type and requires no power.

Bob Beers

[Bob Muzio]

Go with the voltage stabilizer, most likely it's the culprit, but check for a good ground first.
Bob

[ludwig]

The car does have the original charging system.
I will confirm ground straps and check stabilizer.
Is there a relatively easy way to check it? Or should i just order a new one?

Thanks, DK

[charley fitch]

Here is another queation to ask.  With your car changed form positive ground to negative ground do you need a different stabilizer, eg. for negative ground system?  I have seen comments that say yes and those that say no.  Does anyboody out there have this answer to share?
Charley Fitch   

[Bob Muzio]

Hi Charley,
I don't recall seeing one offered for each application. My car's ground has been converted and I have had to replace it for the same symptoms described above.
Bob

[TR3driver]

The stock voltage "stabilizer" will work with either ground polarity.  Internally, it works kind of like a thermal turn signal flasher, there is a resistance wire that gets hot and a bimetal contact that opens when it gets hot enough.  The output has a long-term average of 10.0 volts, but in fact switches between zero and full battery voltage.

A quick and easy test is to connect a voltmeter or test light across the temperature transmitter (on the side of the thermostat housing under the hood).  With the key on, you should be able to see the "flash" as the voltage swings back and forth.  If it is constantly on, then the heater in the VS has failed and it's time for a new one.

However, there are some people selling "solid-state" replacements for the VS, which are polarity-sensitive and do put out a constant 10.0 volts.  Quick check for this is to pull the wire off of the temperature transmitter and check the voltage from the wire to ground.  If it's 10.0 volts, you have a working solid-state VS.

[ludwig]

Turns out the voltage stabilizer was wired incorrectly.
Thanks to all who offered an opinion.

DK