CJ Speedometer Gauge Quick Test

By: John Strenk

 

OK, You know what your doing. You don't need a long explanation. Just a test light. Maybe a DVM.

 

One Warning. A poor broken ground connection or hooking up the plugs incorrectly can quickly burn up the gauges or sensors. Don’t make matters worse. Double check your connections before turning your ignition key to “ON”

Step 1. Start Here

Turn key to ON. Attach your test clip to a good ground.

You may want to disconnect your Ignition coil. These have been known to burn up if the key is “ON” but the engine is not running.

 

 

Step 2: Power test

Check for power at the "I" terminal.

The test light should glow brightly if you’re getting power.

If the light is on go to next step. If it does not work go to Troubleshooting.

 

Step 3: Regulator Test

 Test for flash at "A" Terminal.

The test light should flash if the regulator is working.

If the test light is flashing go to next step. If it is not flashing go to Troubleshooting.

 

Step 4: Temperature circuit test 1

 Remove Temp plug and test for flash at Temp plug: The light should flash as it did in the previous step.

If the light Flashes go to Testing Temperature sensor. If it is not flashing go to Troubleshooting

Test 5: Fuel Level circuit test 1.

The light should flash just like it did in the previous step. Remove Fuel level plug and test for flash at Fuel Plug:

If light flashes go to trouble shooting Fuel Level Sensor. If it does not flash, go to Troubleshooting

Test 6: Temperature circuit test 2

 Momentarily ground the temperature plug. The gauge should go to “H” in a few seconds. Don’t leave the plug grounded for any longer. Remove the ground.

If the gauge goes to “H” then go to Resistance Tests. If the gauge does not move go to Troubleshooting

 

Test 7: Fuel Level Circuit test 2

Momentarily ground the Fuel Level plug. The gauge should go to “F” in a few seconds. Don’t leave the plug grounded for any longer. Remove the ground.

 If the gauge goes to “F” then go to Resistance Tests. If the gauge does not move go to Troubleshooting.

 

For the following test you will now need an DVM

 

 

Test 8. Resistance measurement Temperature Sensor

Start your jeep and allow it to warm up.

Take your ohmmeter and connect one lead to ground and the other lead to the post on the sensor.

Compare your reading to the following chart:

Temp. Gauge calibration:

Room Temp……………70 degrees—200 to 400 ohms
C (cold)........................ 130 degrees--73 ohms
Beginning of band........ 171 degrees--36 ohms
Top of band.................. 242 degrees--13 ohms
H (hot).......................... 270 degrees---9 ohms


These measurements don’t have to be exact below 130*F. Some where in this resistance range though.

If these reading are OK and your gauges still doesn’t work then you need to check your grounds. Refer to the Trouble shooting section

 

 

Test to Base of Sensor ^

Test to Ground ^

Test 9: Resistance test Fuel Level Sender.

Take your ohmmeter and connect one lead to the base and the other lead to the post on the sensor. Also test the resistance to the ground on the frame.

Compare your reading to the following chart

Empty = 73 ohms
1/2 Tank = 23 ohms
Full tank = 10 ohms

Note: If you don’t know the fuel level just expect the resistance to be between 73 and 10 ohms.

 If these resistance readings are OK and your gauges still doesn’t work then you need to check your grounds. Refer to the Trouble shooting section.

 

 

Right to Base of sender ^

To ground,^

Something is wrong, different resistance