To all the regulars out there I say hi. I am totally new hear and have spent my first 7 hrs. reading lots of good information. To my problem. Mine is similar to one posted the end of last month but not due to changing the alternator and my truck is a 91 not a 93. About 2 weeks ago I had new injectors and a new IP installed on my 91 7.3 IDI. I also had a new fuel heater and the housing the fuel filter attaches to replaced. This all due to poor starting and pratically no starting when cold. Anyway the tach just sarted going nuts about 3 days ago which made the truck up shift and down shift. As a wonderful side affect the OD light is dim and does nothing when you try to turn it off and on. With as fast as the problem started it went quickly the next days to no tach, and the shifting went to 2 and 3 manully only. I changed the tach sensor yesterday to no avail. I check all my fuses under the dash and looked for the TECA referred to on that 93 7.3 post. I did find the tailer tow relay that was referred to. I also found no place for fuses under the hood. I am sure it is something simple but hope it's nothing to expensive.