Incorrect speedometer

[D Mann]

That won't work for me. It is percentage based and not actual constant mph.

 

[OdinsRoar]

Speedometer is still 10 mph too fast. At stop , it's on 0, stopping after driving to a light, it's on 0. I have checked the speedometer housing at the five oclock position and the 34 tooth gear. It's correct and in very good condition. It is not a proportionate error, it is a constant 10 mph too fast vs actual speed. I have reset the gauges with the odometer button press method and tried the battery disconnect-tap,tap,tap method.
I am still 10 mph fast.
Help me Obe wan!

What size tires do you have

 

[D Mann]

That is a tool for correcting percentage of speed errors not a constant error of 10mph at all speeds. It wouldn't work in my situation. I did the gauge check by holding the trip odometer button down and turning the key on. The speedometer should go to 20mph, then 55, and then 75.
Mine went to 30mph, then 65, then 85.

 

[KennethS]

Yeah, that is not the typical percentage error, it’a a fixed offset. Never heard of that before.

 

[jonny jeep]

I have reset the gauges with the odometer button press method

This isn't a reset. It's called the actuator test and is used to make sure gauges are calibrated correctly and lamps are functioning.

I don't know what year your TJ is, nor do I know what positions the needle is supposed to point to in later models, so I can't confirm the speeds you quoted above.

In early TJs the Speedo needle should move between the following points during the actuator test.
0-20-55-80-100-80-55-20-0

Since yours is off by 10mph at the references points you've quoted I'm wondering if the needle has ever been popped off before and stuck in the wrong position. I'd be tempted the remove the cluster, remove the clear cover, and see if I could pop the needle off. If it can be popped off, I'd gently push it on a touch, resting against the needle stop. Then I'd push the cluster in without the clear cover and run the actuator test to see what the speed registers.

If still inaccurate as I expect it would be, and the needle is high enough off the face of the cluster, you might be able to grab the shaft with needle nosed grips, which I'd do at the highest registered speed. Then reposition the needle pointing where it should and run the cluster test again.

 

[D Mann]

This isn't a reset. It's called the actuator test and is used to make sure gauges are calibrated correctly and lamps are functioning.

I don't know what year your TJ is, nor do I know what positions the needle is supposed to point to in later models, so I can't confirm the speeds you quoted above.

In early TJs the Speedo needle should move between the following points during the actuator test.
0-20-55-80-100-80-55-20-0

Since yours is off by 10mph at the references points you've quoted I'm wondering if the needle has ever been popped off before and stuck in the wrong position. I'd be tempted the remove the cluster, remove the clear cover, and see if I could pop the needle off. If it can be popped off, I'd gently push it on a touch, resting against the needle stop. Then I'd push the cluster in without the clear cover and run the actuator test to see what the speed registers.

If still inaccurate as I expect it would be, and the needle is high enough off the face of the cluster, you might be able to grab the shaft with needle nosed grips, which I'd do at the highest registered speed. Then reposition the needle pointing where it should and run the cluster test again.

I thought about doing just that. When i did the test i was gonna grab the needle quickly and see if it would click backwards. I was worried about breaking it.

 

[jonny jeep]

I didn't mention above, the needles are magnetically moved rather than mechanical. You can move or hold the needles without causing damage. They will just return to where the magnetism makes them when released.

 

[D Mann]

That's great to know. Thank you. I'll try it today.

 

[D Mann]

Tried to block the needle during the actuator test several times with an eraser so I wouldn.t mark up anything. It failed. The needle still shows 30, then 65, then 85, which are all 10 mph too fast. The indicated speed while driving is still 10 mph too fast at all speeds.