Question about 2004 Ford Super Duty F 450

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2004 F-53 motor home chassis with speedometer lagging about 20mph

Have checked all fuses and found O.K. When problem first started horn was also inoperative, replaced relay in hood area and horn started working and still works but speedometer still has problem. Leveling jacks warning horn also has become inoperative, works normally otherwise.
Please help.

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I know electrical problems are probably the most frustrating things to go wrong. First I would like you to get your alternator and auxillary power generator checked. Autozone and similar can scan it. My alternator had us doing 55mph at a stop and running up miles too!

The generator can put out "dirty" power that is incompatible with delicate electronics.

There may be a speed sensor in the differential. I know some have them there. If not, I am sorry to say your computer may be bad. There are aftermarket devices for adjusting the speedometer for different size wheels and tires. This is done with computer reprogramming. Your vehicle should not have lost its settings on its own. If something is interferring with the readings it is possible to remove that device and your computer may recover.

Your leveler alert horn may be out of adjustment. Test the leads of horn before scrapping it. It may still honk.

If you recently plugged into a trailer park before this came about, you should have some warning panel to test crossed wires. If this is electrical damage due to casualty you may have homeowners coverage. Good Luck

Posted on Jul 31, 2009


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