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am getting ready to buy a 94 f250. When I test drove it, the Od light flashed when stopped (dealer said it meant OD was off because we wern't moving - sure!) After searching I noticed all the posts about sensors.
Data:
7.3 turbo
174,000 miles
No light flash while moving.
Trans shifts normal
Light on at idle
At idle, tach reasd zero
Fluid is clean (may have been changed by dealer)
Question: Since there are no other problems but the tach, is it safe to assume the tach sensor sends inputs to the computer causing the light?
Sounds like it needs a tach sensor. Looking to the driver;s side of the oil filler on these you should see it. A common issue is the insulation separating from the sensor, leading to broken wires, or shorts. Unfortunately they are dealer only for the most part, wiht a few online places too. Hopefully someone will post a link for sources.
You may want to ask how long it's been flashing and if it's been shifting really hard. Does it only flash while idling? If left too long it can damage the trans. That should be taken into account while making an offer.