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Calibrating your Fuel and Temperature Gauge.

For those who need to have everything perfect. One final adjustment....

You will have to remove the speedometer from the case and the individual gauges from the speedometer housing.
To calibrate the temperature gauge you will need to have the fuel gage hooked up at the same time.

Calibrating the Fuel gauge:

First lets have a look at the back of a typical OEM style Fuel gauge.


You probably never noticed the extra slots in the back but those are used for doing a calibration. They are actually quite clever in coming up with such a simple adjustment.

If you look inside an OEM gauge you will see two windings around two swperate bi-metalic strips. One is the often miss-labeled "Voltage Regulator" side and the other is for the needle or indicator movement.

As the windings heat up around the bi-metalis strip, one end of the strip will move. This free end is attached to the needle. The way the calibration works is there is a slot in the end of the needle were the pin on the end of the bi-metalicstrip fits. Depending upon the position of this pin in the slot determines how much the needle moves in relationship to the movement of BM strip. The closer the pin is to the pivot of the needle the greater the travel of the needle. THis is the Full Scale Adjustment. So if your gauge is not reading "Full" when the resitance is 10 ohms then you need to adjust the position of the pin.


THe other adjustment just sets the starting position of the needle or "Zero Adjustment" So if your gauge isn't reading empty when it's at 78 Ohms then you need to change this adjustment.

Note these adjustment are interrelated meaning that if you adjust the "Zero Point", then the needle might not reach "Full" so you will have to go back and re-adjust the "Full Scale" adjustment.

Start with the Zero Point first.

I attached the proper resistance (73 ohms) to the "S" terminal and ground and attached the power and ground leads.

I used 10-32 nuts and wire lugs to make the connection easier.
THen I adjusted the Zero point to read "E" as best I could using a flat bladed screwdriver. Then you replace the 73 ohm resistor with a 10 ohm resistor and adjust the FUll Scale adjustment. Note it might take a minute for the needle to Stop moving so you might want to read a chapter in your FSM while your waiting. :). It also makes several jumps when going to "F". This is normal.

Calibrating the Temperature gauge.

You will need to have the fuel gauged hooked up to power and ground and run the "A" post on the Fuel Gauge to the Temperature gauge as shown below:

(insert Picture)

Again start with the Zero Point first.

I attached the proper resistance (73 ohms) to the "S" terminal and ground and attached the power and ground leads.

(Insert Picture)

I used 10-32 nuts and wire lugs to make the connection easier.
Then I adjusted the Zero point to read "E" as best I could using a flat bladed screwdriver.

Then you replace the 73 ohm resistor with a 10 ohm resistor and adjust the FUll Scale adjustment.

Note it might take a minute for the needle to Stop moving so you might want to read a chapter in your FSM while your waiting. :). It also makes several jumps when going to "F". This is normal.

(Insert picture)

Calibrating Replacement gauges

Now the replacement gauges I have work a bit differently. Mine was quite bent inside and needed an adjustment. Maybe yours was knocked out of cal also.


The Zero and Full Scale adjustment are in one place. Put the screw driver in one slot and you can adjust the Zero Position. Turn the screw driver 90* and you can adjust the full scale movement. The pin and needle mechanism is the same as the OEM gauges. THe screw on the side is for adjusting the regulator. It has a funky screw so you don't accidentally mess up this adjustment.


Irregardless of how the adjustments work internally, the procedure is still the same as above. If you can't get the gauge to work properly after all this then I would recommend you send them back and get another set. There have been some "Quality issues" with the vendor.

The regulator adjustment will help you match a new Gauge with on old one. I normally never have to adjust this unless the movement is slow or bumpy.
 
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