Classic/Antique Car Repair/eletrical

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Expert: - 4/28/2009


Question
i have recently purchased an 1991 dodge d-150. the engine and tranny have been replaced,everything works execpt for the speedometer. ihave checked the fuse block,and there are no blown fuses.the speed sensor has been replaced with a new one. i have changed the speedometer head and circut board from an local junk yard, with no results. i was  wondering if there was another set of fuses i dont know about. also the truck is an automatic now,if that makes a differance. thank you for your help in this matter

Answer
The speedometer is electronic in this truck. The speed sensor sends a signal to the engines operating computer. That signal is used to control the fuel mixture, spark timing, cruise control, transmission shift points, and the speedometer. The diagnosis for a speedometer problem is to get some one who has a scanner that will plug into the computer and read the computer output. It is very possible that there is a computer problem. If the computer is telling the scanner that it is receiving the signal from the sensor and giving output then the problem is wiring between the computer and speedometer or the speedometer. But the starting point is the scanner check of the computer.
Brad

Classic/Antique Car Repair

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Brad Sears

Expertise

All automotive including antique and collectible. However if the car has been modified I can only answer in general terms and maybe get you pointed in the right direction.

Experience

Automotive tech instructor. Syndicated auto columnist 1970's though the early 1990's. Syndicated auto radio talk show, Ask Brad About cars, CBS Radio 70's through 90's TV Show "Last Chance Garage" 1980's PBS-TV syndicated. Auto instructor for the following companies: Fram Autolyte Holly Carter AMF Ford Motor University Of Conn Blue Hills Technical School Sugar River Technical Center Grew up in a family garage in Needham Mass and turned wrenches from the age of 14.

Publications
Manchester Union Leader, Nashua Telegraph, Motor Service Magazine, Yankee Magazine, Popular Mechanics (Saturday Mechanic early 80's), Los Angeles Times, New York Times, and lots more.

Education/Credentials
More than I care to remember. Basically Franklin Technical Institute in Boston, Northeastern University, Fitchburg State Teachers College, Tufts University, and a lot of factory schools along the way.

Awards and Honors
Moto Award winner. And much more.

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