tachometer question

Well, Ive tried the battery disconnect and reconect on the tachometer issue ... no luck. A gentleman at the rv dealer said it is most likely a broken cable to the tach ... I'm not sure if it is a mechanical tach, guess it would be best to take it to a Ford dealer not an RV dealer.

Go to Ford's Truck Body Builders Advisory web site (Click Here). Has the specs you are looking for concerning chassis 12VDC distribution but it will not show what Damon might have done tapping into what Ford provided.

For the electrical info you are looking for Click Here and go to the last two pages.

Concerning the tach error, physically disconnect the chassis battery, and maybe the coach batteries also, for a few minutes to clear the chassis computers. When you reconnect you might see all the gages swing thru their total movement as the computers process thru their power on self test.

Lucky enough my breakers and fuses in the back of the rig, for the coach are labeled. I am most confused of the 12 volt fuses under the dash and 2 boxes under the hood.
I'm going to try disconnecting the battery tonight and see if the tach resets.

tpwelker wrote:
I have a chassis manual but nothing is specific to my RV. Example being the fuse box(s) I have no idea of what fuse does what. None of the fuse panels match mine.

While you are home turn everything on and then pull the fuses or flip the breakers and see what shuts off...then label them

might save you some headache on the road someday

I have a chassis manual but nothing is specific to my RV. Example being the fuse box(s) I have no idea of what fuse does what. None of the fuse panels match mine.

An owners manual would likely have nothing to help you in it. You need a manual for the chassis that you might find at am auto parts dealer.

My 99 Jeep did something similar, the battery went dead while we were gone on vacation in the winter (Jeep at home in garage). I charged the battery and it started right up but when we drove it the tach and speedo didn't work. Went to Jeep dealer and talked to mechanic, he said probably a bad computer, I went home and unhooked the battery and hooked it back up. That was 5 years ago and everything has worked perfect since then. Try unhooking the battery and see if that does it.

That is a typical circuit. Yours could be an IC. Not much to the circuits. May have blown a part. If it is an IC you will have to see if you can find a part #. Google part # and get a source. If it were mine and I couldn't find the IC I would rebuild with componets. You would need to calibrate for full scale.

tpwelker wrote:
haha the tap method was the first thing I tried. I just don't understand what would have made it climb from 0 to over 6 without the key in the ignition. I did have the battery on charge, maybe that did something?

Next test would see if removing the 12 volts to the tach electronics. Basically tachs change digital to analog to deflect the meter. If removing power the meter drops then it is the electronics not the meter. I doubt there are many parts in the electronics.