Speedometer needle jumping

**mrmrrck** · Sep 09 2010, 04:07pm

My speedo is now jumping while in Park, Reverse, and Drive. If I'm setting still and the RPMs are under 1500, the needle jumps from 0 to up around 30 and back to 0. If the RPMs are above the 1500 the needle stays down on the 0.

Where is our speed sensor located?

It's electric right?

Can I pull it and clean it?

This just started last weekend.

It doesn't jump in Neutral.

Thanks

Oh yes... My truck is an '01 XLT with a 3.0 and Auto...

**mrmrrck** · Sep 10 2010, 08:45pm

Anyone??? I know I'm not the only one to have this happen to them...

Thanks

**CumminsRanger** · Sep 10 2010, 08:58pm

mine bounces around on accel and decel, but its gear-cable driven

***Kaz*** · Sep 11 2010, 12:48am

speed sensor is going to be in the rear diff. its also the abs sensor. any issue with your brakes lately?

**Blhde** · Sep 11 2010, 02:33am

IIRC, vehicle speed sensor changed from the rear end to in the trans for 01+.

**mrmrrck** · Sep 11 2010, 10:10am

I changed the front rotors and bearings a couple months ago.

I do have a sensor on top of the rear end. So it that my speed sensor? Do I need to drain the fluid to change it out?

Thanks

**BluRanger8** · Sep 13 2010, 10:09am

As Blhde mentioned, the 01+ Rangers use a speed sensor in the transmission for the speedometer input. There is still a sensor in the top of your rear end, but it is used only for the ABS. 98-00 were the only years where the ABS sensor in the rear end was pulling double duty as a ABS sensor and speed sensor for the speedo.

I once had a similar issue with a bouncing speedometer needle at idle and low speeds in an 03 Edge. Defying all reason, it turned out to be a bad battery... even though it still had enough juice to start the truck (as long as it didn't sit for more than 3 days without being driven).

**mrmrrck** · Sep 13 2010, 01:32pm

So is this sensor "IN" my transmission? or screwed somewhere "ON" my transmission?

Do I need to drop the tranny's pan?

Thanks

Is this what you're talking about?
http://www.rockauto.com/catalog/rafr...parttype=10634

**ex90ranger** · Sep 13 2010, 01:44pm

I know exactly what your problem is. it is either a battery that is weak and not holding voltage or your alternator is starting to go out.

On my truck, when ever my batteries are low and the air compressor kicks on the voltage drops to around 9 or 10 volts. When this happens my needle just sits there and "quivers" until the compressor shuts off or if I press on the gas and rev the engine up a bit to let the alternator produce a little more current. Also, if you watch your trip meter you will see that when your needle is doing this it is rolling your mileage.

**BluRanger8** · Sep 13 2010, 02:12pm

Posted by mrmrrck

So is this sensor "IN" my transmission? or screwed somewhere "ON" my transmission?

Do I need to drop the tranny's pan?

Thanks

Is this what you're talking about?
http://www.rockauto.com/catalog/rafr...parttype=10634

The sensors listed on RockAuto's page contain both the rear ABS sensor and the speed sensor in the transmission (bolted to the outside of the transmission tailshaft). The short sensors with the blue insert in the connector are the ABS sensors for the rear end. The longer ones are for the transmission. That being said, after hearing ex90ranger describe the same low voltage problem that I was experiencing, I'd certainly check the battery and alternator first.

**93PurpleRanger** · Sep 13 2010, 02:18pm

Mine jumped when i first bought it which was a year ago and i put a new battery on it and it still jumps and i think if the alternator was going bad itd be done by now. would there be any other reasons for this if it doesnt help mrmrrck

**ex90ranger** · Sep 13 2010, 02:47pm

If that is the ranger you are talking about in your avatar, yours is cable driven. You can pull the cable off the back of the speed-o and loose from the tranny and slowly shoot some lock graphite down it from the speed-o side and spin it slowly on the tranny side. Or just replace it, but it's kind of a pain either way.

**ex90ranger** · Sep 13 2010, 03:49pm

http://www.youtube.com/watch?v=7jAb5Szx27E&hd=1

here is what I was talking about, I just uploaded this to youtube to see if this is the same problem you are looking at.

**mrmrrck** · Sep 14 2010, 07:16pm

Wow, Looks like I'll check my electrical system.

I have a new battery (Optima red top) and Explorer Alt (130 amp)

I've had the alt checked (benched) at Oreily's. They said the stator was going bad. So I took it to a rebuild shop and they checked it and came back and told me that it tested great (14.4v and 140amps). So I put it back in my truck. The volt gauge always reads just under or touching the battery bottom corner.

My needle jumps only at idle. Any gas at all the needle stops. Also it jumps up to 30. I'll try and take a video of what it's doing in the morning. I never checked the trip while the needle jumps. Looks like I'll check that also.

Thanks

**ex90ranger** · Sep 15 2010, 07:07am

One thing you can try, I don't know if it would make a difference or not, is run a wire from your alternator output to the power distribution box under the hood. Something no smaller than a 4 gage wire. It is possible that the fusible link that’s installed in the factory harness has started to go bad and it isn't letting full voltage get to the system or to the battery to charge it. Also check any grounds you can find and see if one of them has gotten messed up. Good luck man, tracking down electrical gremlins is one of the worse things a person can do.

**mrmrrck** · Sep 15 2010, 08:49am

Grounds I've checked already. I'll try a new wire..

Thanks

**mrmrrck** · Sep 15 2010, 01:01pm

Went into town today, needle was jumping alot, (every street light) Tried to record with my phone. That didn't work well (blurry) When I got home I took the camera out to video the speedo. Here it is off Photobucket.

The 1st 10 seconds shows the needle jumping. The last 10 the needle is sitting still.

**ex90ranger** · Sep 15 2010, 06:38pm

Your voltage is definitely in that magic zone because that’s right about the same spot that mine starts doing it by looking at your voltage gauge. Mine is just a hair lower but not much. I would stick a volt meter on the input to your power distribution box, and if you don't have one they might have one down at AutoZone or someplace like that you can use. Because you are deff low on the voltage.

**mrmrrck** · Sep 15 2010, 08:14pm

Yes I'm low, I'll measure the volts in the morning. I think I have some 4ga wire around so I'll run a new/extra line to the distro box.

If the wire doesn't help, then it looks like I'll have to get another alt.

BTW...Seems like the volts drop after the engine get to operating temp. It reads in the middle or so of the battery (gauge) when cool, then drops after warming up.

? Can fusable links go bad once they get hot. I've checked continuity through them and they read (0). So they are not open. I checked when everything was cool, not hot. Looks like I'll check them after the motor gets hot.

Video was recorded with the engine at operating temp...

**ex90ranger** · Sep 15 2010, 08:19pm

Electronics can go back with heat, and the diodes that regulate the current and voltage output of the alternator are a prime candidate. Also batteries sometimes can get a little funky when warm but it is pretty rare. And yes, I have seen some fusible links that still pass some power but not much because they are starting to go bad and heat can affect that.

**mrmrrck** · Sep 16 2010, 11:32am

Checked the volts today. Here is what I found.
At the battery.............. 14.2v
At Distro box............... 14.2v
Those are with the engine NOT at operating temp

At operating temp
At the Battery.............. 13.0v
At Distro box................ 13.1v
At Alternator................ 13.4v

Not a big drop, but a drop nevertheless.

**morsedog** · Sep 16 2010, 12:29pm

I wrecked a ranger a few years back. I have sold the ranger since then, anyway it's electrical system got all funny on me(no lights, blinkers, or speedometer) after the car crash. I thought it was the alternator but I had it checked and it was fine. I replaced the flasher unit in the fuse box and replaced the headlights and that got it all working again. Electrical systems can be the most confusing problem. My suggestion is check your fuses and your wires to make sure there is no shorts, it might save you some time fiddling with the tranny.

**diver7967** · Sep 17 2010, 10:50pm

When you check your voltage when the vehicle is running are you using a digital meter or analog. If you are having a voltage ripple you will be able to see it on the analog well, not really on the digital. If you are seeing a ripple check your "voltage regulator" fuse under the hood. I had similar effects when this fuse went bad. I ended up replacing an alternator and battery before I noticed this. The face palm left a bruise....lol

**ex90ranger** · Sep 26 2010, 11:39pm

So did you ever come up with an answer for this? I am genuinely very interested to find out what’s wrong with it.

**mrmrrck** · Sep 27 2010, 01:40pm

Not yet, Alternator still in the shop. I'll be chasing the wires down this week. Might get a new pigtail.

**mrmrrck** · Oct 01 2010, 08:22pm

Been a busy week. Got the Alternator back... nothing wrong with it. The shop tested cold and hot and got good results everytime.

The small wire that goes from the back of the alt back to the plug has a little bad wire on it. I can move it around and my volt meter changes a little. If I disconnect it the battery light comes on. I'm getting constant voltage thru the fusable links while I move them around. So it looks like another pigtail for my truck.

I'll keep you posted...

**ex90ranger** · Oct 01 2010, 09:42pm

please do

**mrmrrck** · Apr 01 2011, 11:15am

Wow, I didn't realize how long I've had this problem...

Update... Changed OSS and put a new pigtail on the Alt.

Still no change except my voltage gauge reads a little higher now. Needle still jumps.

Also now when I turn on my lights (while the needle is jumping) the ABS light comes on. When the needle is NOT jumping the ABS is off.

I'll have to check the ABS sensor on the pumpkin next...

Still tracking down grounds.

Got some 4ga for the ALT/Distro box... (might try that)(Big 3)

**mrmrrck** · Apr 02 2011, 02:24pm

Update:

Changed the ABS sensor on the pumpkin... Still no change.

**ex90ranger** · Apr 02 2011, 10:58pm

hmmmmmmmmmmmm

I am still going to say bad voltage or ground. have you stuck a meter on the fuses in the dash to see if there is a difference in voltage there from under the hood?

Speedometer needle jumping

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