hey i have a 2006 f350 and the speedometer is jumping around. like i am sitting still and one day it was reading 15 and today i was reading 80 mph. I replaced the rear speed sensor and it wnet away, but now it is acting up again so i replaced it with the old one and again it went away. does anyone know what the value of the sensor should read so i can check it with a volt meter? i also unpluged the sensor and it is still reading when it should be zero on the speedometer. any suggestions to what it could be?

 

i'm just guessing as i have never had this problem. but if it were my truck i would start by unpluging the batteries (negative side first) and then plug them back in to semi "reboot" the computer. also it could be a loose electrical wire connection to the dash??? idk here is a BUMP to the top for you.. hopefully someone else can help.

 

If it's cold where you live, you could have the dreaded "frozen speedo". (I named it that) Mine won't work most of the winter unless the truck is kept in a heated garage. Once spring hits, it goes back to normal.
It might not move off zero, might stick at the speed I was going last, and then add it onto the speed I'm going later...

 

Thanks I have done the battery and it works for a few then not off as bad. I like the frozen speedo. It is not the bad here and this all started before the cold got here and it is not the cold here as other places. I just wish i could get a wiring diagram to really see how this system works. I do have the abs light on but that is cause of the front right sensor and the ficm computer was just replaced thanks for some ideas.

 

Mine just started doing this last week.

I live in SW Tx, but we went back to NC for Christmas - I was driving one day and looked down and was doing 60, a quick glance at the Scan Gauge II and it showed 35. It stayed that way for 2 engine restarts, then was only off by 15 MPH - a few engine restarts later and it was back to normal. Fast-forward another week and 1,400 miles back to Tx and this morning it's off again by about 15 MPH.

Of course from SW Tx to NC was a pretty big change in temps - in fact we had a few nighs in the teens and 5 inches of snow on Christmas day... so it could truly be a temp (frozen) condition.

I think it's odd that the analog speedo show the speed being off, but the miles are matching up (ran a measured mile and turned a mile on the odo) and the SGII shows that the computer is reading the correct MPH... so I think it's a problem with the analog speedo itself.

I keep an eye on mine and see if there are any changes... glad I have the SGII...

 

Although it is not as cold here in VA as it is in Canada by any means, that is my exact problem. When it is below freezing my speedometer acts up as noted in the other posts. Any fix??

 

Not for me - they want $800 for a new cluster plus installation. I just left it. I can use the gps if I really need to, but I can judge the speed pretty good.

 

Ok thanks. I assume you are referring to the instrument cluster in the dash.

 

You might check with one of the companies that repairs instrument clusters to see if that's a repairable issue. Might be something the average guy can do.

 

I bet you guys had the same problem I had.

See FORD---TSB 07-11-2. See link.
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https://www.ford-trucks.com/tsb/fulltext/show_article.php?tsb=07-11-2
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The face warps when it is cold, the needle hangs up on it, the computer senses that and tries to adjust the needle.

I fixed mine a few years back (FOR FREE) and it has been working great ever since.

First take the cluster out of the truck and get it on a workbench. I could see on mine where the black center part (of the needle) was rubbing on the face. I wanted to take the needle off and file it down a little bit to give it more clearance, so that it wouldn't rub on the face. I do not think the needle pulls off because I pulled at it and it seems very tight. I think there is a screw under the black cap. You may have to use a heat gun to get the cap off, but I wasn't going to do that. Remember this unit is expensive.

So I took a piece of cardboard and a piece of 220 grit sand paper. The cardboard is needed to protect the face. The needle does have some play, so you can move it in and out a little bit. After you get the sandpaper under the black part of the needle just press down on the needle and move the sand paper back and forth. Turn the needle back an forth so that you take off about the same amount the whole way around. You can fold the sandpaper if you need it thicker, or use thicker cardboard. The plastic sands pretty easy. I sanded about 1/8th of an inch off of mine so it has plenty of clearance.

 

Thanks but as it does not freeze here but every so often I will follow Mr. Irwin's route and use the tach to judge speed when the speedometer fails.