speedometer error when cold

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Mar 3, 2003 | 05:12 PM

karlg

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Joined: Feb 2003

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From: southern Illinois

speedometer error when cold

I have a 1991 Ranger XLT, 4.0L, automatic transmission, 157000 miles. Whenever the temp is below freezing, the speedometer reads fast(usually 10-20 mph). As the engine/transmission warms up, the speedometer will gradually return to the "correct speed". This does require more driving than just the thrmostat opening up. Tach doesn't seem to be affected. Explanations?
Karl

Mar 4, 2003 | 04:37 PM

aerocolorado

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speedometer error when cold

Karl, welcome to FTE!

Just so you don't feel lonely, I've had this problem on the same engine/transmission ('91 Aerostar) for several years. I have asked in several different forums and it remains a mystery as to why the speedo acts up like this. If anything, you would expect it to read lower when cold, not higher. Again, the same result, once the transmission warms up, the speedometer returns to normal.

I've checked the cable for wear, drag, corrosion and the gears for stripped teeth or loose mounting...anything that would begin to explain this, but everything is within specs. I've even had the entire transfer case apart during a rebuild, hoping something definitive would turn up. Nada, zilch.

In the meantime, look on the bright side. You and I can drive "80 mph" past a cop in a 60 MPH zone and get away with it.

Last edited by aerocolorado; Mar 4, 2003 at 04:43 PM.

Mar 4, 2003 | 04:47 PM

CowboyBilly9Mile

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From: Eastern WA

speedometer error when cold

You are not alone! I had this start, conveniently, after the warranty ran out. I replaced the speedo cable, but it did not help. I have always suspected that if the speedo were removed and cleaned that the prob may go away, but have never tried it.

Mar 4, 2003 | 04:51 PM

karlg

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From: southern Illinois

speedometer error when cold

Thanks for the welcome! I've had the problem for more years than I can remember. I agree about expecting it to read slow rather than fast. I quess my interstate speed by the rpm's...2000rpm's=65mph.
Thanks again,
Karl

Mar 6, 2003 | 09:28 PM

Andywk

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speedometer error when cold

I have also had this problem. Just like you said during cold weather. It will eturn to normal and has never caused any other problems. Mine has many many miles on it. I have just learned to live with it.

Dec 12, 2003 | 02:55 PM

aerocolorado

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Seeing as how cold weather has set in again with this attendant nuisance, I thought I would update this thread as I finally found out what causes this problem.

According to Ford Technical Service Bulletin 92-12-09, the cause is due to insufficient lubrication within the speedometer head during low temperatures. The problem resolves when the head is warmed up. The cure is to replace the speedo head with a new updated version.