I have a 2002 F350 CC 7.3 w/ 46K on the clock. I hauled my trail jeep about 120 miles round trip on Sunday with no issues at all. My wife and kids and I took a road trip today from Middletown, PA to Lock haven, PA about 120 miles one way. The truck ran AWESOME! 17.9 mpg with about 500 lbs of tools, generator, fuel, and such in the back. Upon our leaving to come home, the dash dies and then the motor dies. I had no power anywhere, not even to the 4 ways. I pulled the fuse panel cover under the dash and could not find any blown fuses. After a few minutes, I tried the key and I had a relay clicking like crazy. It was the "injector drive module relay." I called the local Ford delear and they had none in stock. WTF?!?! I called Advance Auto and they had 8 in stock. I got one, put it in, truck fires up but still no dash, no dash lights, no speedo, no odometer, no nothing from the dash. I had no radio, but I had lights, 4 ways, blower motor, etc. So I drove it about 1 1/2 miles to the Ford dealer. The service manager came out to help me, they do not have a diesel mechanic on staff, another WTF?!?!?! We pulled each and every fuse, none blown, no more clicking relays, no nothing. I crawled under the hood, wiggled the battrey cables and everything came back to life. We hopped in the truck, said a few prayers, and drove 120 miles home with no issues. My question, if the battrey cables were loose, why did I still have a blower motor, power seats, but not dash lights or anyhthing else? On the DS battery there is a large crimped conection on the positive side that runs under the radiator support over to the battery on the PS. Could that be corroded enough for me to loose power? Does one battery run one set of things and the other battery run other sets of things? Are the batteries in series or parralel (not that I now what that means, but somebody does, I am sure). Any ideas, suggestions, anything!?!?!??!

 

I,m subscribing to this one Earl. Bump.

 

actually the ground or the power are really the only way to loose all functions. a poor ground might let some stuff work but you might be taxing it by trying to use to much stuff. a poor connection could do that give you some stuff and no others. the batteries are in parallel, if they were in series the truck would be a 24 volt system. you need to remove all the grounds you can find clean them up and re-attach them. remove the positive cable from the starter and clean it up. you can never have to good a battery connection neg or pos. never.
you may have had those functions because they may not be a voltage sensitive meaning they might work at low voltage but the other stuff wouldn't. a poor ground (or positive) might only let through say 8 volts. very hard on the trucks elec system. as the volts drop in a elec circuit the amps increase, amps equals heat, heat equals smoke, smoke equals money....
because the batteries are in parallel they each run they truck combined, they act as one battery. its very important to have both batteries be identical.
clean up your connections, check the batteries (load test), check the alt (Load test) repair as need and thank what ever you call a higher being that you found the problem. I'm sure that the ford dealership would love to have had you in the shop for that one. $$$.
good luck

 

Earl, our Canadian brother got this right, clean/tighten them conections.
And welcome to FTE

 

Check you main wiring harnesses under the dash. They have been known to work themselves loose causing the problems you described.

 

How would I go about checking that? Where do they work loose from?

 

Battery connections or battery them selves are the problem. When you hear the clicking under the dash, it is usually the bats, or connections. Check them all and have a good ride.

 

I agree, a bad battery connection is likely, but the harnesses I am talking about are on the drivers side near the cab. It's where all the wires come out of the cab and into the engine compartment. Make sure all are tight.

 

I pulled all the battery cables off today and cleaned all the gunk and funk and nasty gunk that was all over them. I cleaned the posts, the clamps, the tops of the batteries and tightened everything down nice and tight. What brainic made the battery cover on the DS part of the airbox? I did notice that I have two different batteries. I have a Motorcraft and a NAPA. They are both the same CCA, but I am assuming that the Motorcraft is original and the NAPA is a replacemnt. How much of an issue is this? I hate to spend money on two new batteries if I don't need too. Thougts?

 

Your batteries are only as strong as your weakest one. For best results, you should always replace both, or you will continue to have problems. Any idea how old the NAPA is? Did cleaning help anything?

 

No idea how old the NAPA battery is, but it looks pretty new. I guess I will wait till it lets me sit again.

 

if they are the same cca, ca then they should be fine, test that older one to make sure its still up to snuf.
there is a date code on each battery, napa should be able to tell you, or any good auto parts store, how old they each are. to many people wait for the battery(s) to give them a problem before they replace them.
a bad bat can take out the alt long before it leaves you stranded.
chances are if you have gunk around the bat terminals then you should check the other truck connections from the bats just to make sure that they are good and clean.
good find . the cheap ones are the best.

 

Sound to me you need to take batts out and altinator out and haul to the nearest auto parts store and let them do a load test on the batts individuly and check output on alt.. P>S> ALWAYS replace your batts in pairs and every three years at the latest good or bad just change em and you will not be typing on here!