Need help with water temperature gauge

[RockBit]

Gary -you are the man. I redid the test today with the sensor case grounded. On the 10V converter the gauge indicated just a hair under 100C (local elevation is 430 feet). On the 12V supply the gauge showed 98C. All components seem to be working well.

Thanks for the help from everyone.

[patrickt]

Originally Posted by RockBit

Gary -you are the man. I redid the test today with the sensor case grounded. On the 10V converter the gauge indicated just a hair under 100C (local elevation is 430 feet). On the 12V supply the gauge showed 98C. All components seem to be working well.

Thanks for the help from everyone.

I would still use the voltage regulator, even if it's a nuisance to wire in. Remember, your alternator can kick your system voltage up to close to 14 volts, which starts to make a difference on the gauge.

[RockBit]

Originally Posted by patrickt

I would still use the voltage regulator, even if it's a nuisance to wire in. Remember, your alternator can kick your system voltage up to close to 14 volts, which starts to make a difference on the gauge.

Patrick - I agree with you and will install it. Since I have the dash out it won't be hard. According to the Smith's website, the water temp, oil temp, and gas gauge should all be powered by the 10V regulator. That's what I'm gonna do.

[patrickt]

Originally Posted by RockBit

Patrick - I agree with you and will install it. Since I have the dash out it won't be hard. According to the Smith's website, the water temp, oil temp, and gas gauge should all be powered by the 10V regulator. That's what I'm gonna do.

What's funny is that I have one Smiths electric gauge on my car, other than the ammeter -- and it's the fuel gauge. And I have even had to pull my dash and replace it entirely over the last decade. And it doesn't accurately reflect the gas level changes. And it's always annoyed me slightly. But I've never gotten around to wiring in the 10v regulator to make it work properly. Ain't that a perfect example of the shoemaker's children going barefoot.

[strictlypersonl]

Unfortunately, there's no way for a standard mechanical sender/gauge to respond linearly to the fuel level. The combination of a tank with a slanted bottom and a sender float that goes in an arc makes that essentially impossible. In a production car with an analog gauge, they re-calibrate the gauge face to match the tank contents, and the tanks are usually flat-bottomed.

[patrickt]

... well, that's why I just fill it up when the odometer hits 100 miles anyway.

[66AC]

#375 has been given a nickname a long time ago... "Half Full".
Which is the typical reading on the gas gauge...
You'r right, about 100 miles in and we find some 93 octane for Half Full.

[patrickt]

But I have a Smiths "negative earth" 10v regulator over in a cubby hole of the garage desk, right next to the 10-32 1" cap screw, with matching 6 lb. tension spring that I searched hard for as a perfect Holley secondary stop screw replacement (makes adjusting secondaries at idle super easy) then never bothered putting in, and a new Sunbeam Tiger shifter boot (way better than the torn one that's been on there for ten years), again, waiting for installation, and a few other "projects" that I never seem to get to -- regardless of how simple they may be.

[RockBit]

The results are in. I rewired the power to the gauges so that the water temp, oil temp, and fuel gauges were supplied by a stable 10 volts, using a DC voltage reducer from Power Stream. All other gauges are still supplied by the normal car voltage.

I put the dash back in and took a short drive to get everything up to temperature. Everything seems to work fine, but the fuel level is still on empty. There is between 3and 6 gallons in the car, so maybe there is not enough to register yet. I'll fill it up in the next day or so.

The voltmeter is also working now. I had the power and ground switched. When the car is running, it now shows 13 to 14 volts, depending on the engine RPM.

All is well. Thanks again for the help from everyone.