So I assume it is definitely the TECA... I will start looking for another one I guess unless anyone has any other suggestions

 

I ordered the new TECA today...hopefilly it will get here quickly. I have been tracing wires and so far it seems all the power is getting to the computer but the signal is intermittent from the computer to the tach. It doesnt make sense to me...

 

To me it sounds like you have an internal problem in the TECA, keep in mind that each input and output inside the TECA is mostly seperate from each other so one part can fail and not effect other areas. The only thing that effects everything is the 5v reference line that goes to everything inside the TECA and the map and TPS sensor. Thats why I wanted you to test that one to rule out a shorted reference line. If I was in your shoes right now I'd be trying another TECA and see what it does.

 

Well, started the ford up this morning and it was warm outside..tach was working..tried it periodically all day and each time I started the truck the tach was working that is until i started it after a cool front blew thru and it rained a little bit...now nothing again. I am waiting on a new TECAand will try it out when it arrives. Hopefully it will work..I am curious as to why it would stop working when it rained and got cooler though. I didnt see anaywhere where wires were wet and the truck has not been driven, just started up periodically thru the day

 

Well...the remanufactured TECA arrived today and I put it in. I followed your advice and got the 1994 upgrade and used the transmission exchange post info to get the right part number.. started her up and voila! A functioning tach and better shifting transmission to boot! Thanks so much for all the help and I dont know what I would have done without this wonderful site

 

What does it mean if the 5 volt reference line isn't working? I'm having similar issues and have checked all of the items listed above. Tach works when I jumper wired the pins and good grounds but no power to tps or map sensor. Where do I look now?
Thanks for your advice in advance.

 

I don't have an automatic myself, but I'd be tempted to simply get a small 5V supply(USB car charger for example), and just hook the +5v from that to your 5v reference line(and ground to ground, obviously). See if backfeeding it power works.

But that's just me...

 

I am having the same problems. I need clarification on the Teca location. I am confused with some of the info I have found online. I found a device behind the hood release buried the wall cavity inside passenger compartment. It that it or is the Teca in the engine compartment? Is the TECA only accessible from the drivers side front wheel well, by removing the outer plastic fender? Help much appreciated.

 

 

Mine is a 1991 F250, Made in 10/90. I attached a pic of a conn that is on the firewall, passenger side in the engine compartment. Do you believe that it is the TECA conn?

 

 

After using the jumpers on the teca, my gauge came on, however the OD light would not work when I hit the button. What does that mean