Have a 2006 F250 and was driving down the freeway and lost the radio, all gauges, power windows. When I started to get off the freeway and started braking, everything started working again. It kept doing this driving on surface streets for a while too. Lose power, but would come back on when braking. Had the batteries checked and were good as well as the alt (13.25V). This was friday afternoon, went to start it monday morning and the batteries were dead. Remote lock wouldnt even work. Any ideas or direction to start looking for the problem? The deal with everything working again when the brakes are applied is whats really screwy to me.

 

were you braking hard enough for weight shift to be putting pressure on
things, or would it do this if you just touched the brakes enough to light
up the taillights?

have you added any wiring for stereo, navigation, home theatre,
warp drive, anything like that?

could it be that the main cable to the inside cab fuse block is getting
pushed on or tugged by the brake linkage when you operate the brakes,
and causing a loose connection to get tugged on, making a better connection?

were the batteries dead at the terminals, or was it just power to the
inside fuse block that was gone on monday morning?

if you have a clamp on meter that does dc amps, clip it onto the main
battery cable, and see how many amps are being drawn when you turn
on a good sized load... if you have a 15 amp load connected to your
cigarette lighter, for example, and you have a solid 12 volts measured
at the battery terminals, but your batter cable isn't flowing 15 amps,
then you can start wiggling and looking for the poor connection.

in my case, if i power up the stereo, select spoonful by cream, and set
the volume level at 28 on the alpine head end, the drain on the batteries
will be an average of 85 amps, with peaks going to 190 amps.

and everyone for a block and a half will know that i have good battery
connections, and can therefore rest easy.

 

I had the same kind of thing happen.
It was the plug on the back of the alt.
You can get a new one for about $15.

 

Could be a harness is rubbing on the brake pedal linkage. More common on the trucks with power adjustable pedals. Next guess would be grounds. There is one for the cab on the passengers side floor to frame (under the truck about even with back of door opening). Also on my '06 there are several grounds on the inside of the drivers side fender, stacked up on one bolt just below where the hood closes. Those might be worth a look. Could also be a relay going away, cant point you to the right one on an '03 but check for one being hot or making a buzzing noise when the problem is happening. Don't forget to check both fuse panels. If youre have a meter that can measure amps, disconnect the batteries neg cables (both) and put the meter between one of the batter terminals and it's cable. If I remember right it should be much less than half an amp for the radio and PCM memory. If it's high, start pulling fuses till it drops, that will get you on the right circuit. Good luck and Welcome to FTE!

 

Nothing new was added to the truck recently and it is a KR with the adjustable pedals too. Everything wouldn't come back on as soon as I pushed on the brake with a light touch, but when a shift in weight was sensed. Haven't had a chance to troubleshoot this week due to work, but looks like I have my day filled for tomorrow! Will try all your suggestions and let ya know what I find.

 

i'd be looking under the dash to see what loom is near the brake pedal
first, then like the man said, grounds.

good luck.

 

Its a charging problem. When the PCM sees low voltage it'll shut down accessories to preserve power for engine operation.

 

I'm leaning toward a charging problem as well, but the deal with the accesories coming on when the brakes are pushed is whats confusing me. Tried to jump start the truck this morning and the batteries were so dead it wouldn't even jump. Pulled the batteries and took to auto parts store o charge them and their chargers kept kicking them out as bad batteries. Both of them. Only 1.5 year old batteries from Ford so took them back and got new ones (for free). Just installed them and it fired right up. But, the battery light came on and the same accesories dropped again. Shut off the truck, started right up and they were working again. Should I start looking at the alternator as the culprit?

 

Battery light on these trucks are pretty much right on. I agree with the charging problem.

 

The brake lights must be closing an alternative path to ground, or the signal to the cluster. You'd have to start at the alternator(assuming it really is good), and work yourself to the dash looking for loose or corroded connections.

 

Pulled the alternator out to have checked tomorrow. Will see what comes of it. Connections to it were good. Does anyone have the schematics for a 2006 F250?

 

One thing I forgot to mention. On friday when all this started, both batteries were wet on top by the vents like they were boiling over. This is also why I'm still thinking its the alternator.

 

Took the alternator to 2 different stores to have it checked and it came back as bad at both. Guess its time to find me a new one! Any suggestions on a good one and should I up the amperage?

 

this is something you would see being caused by to much ac voltage.. basicly bad diods

 

Bad diodes means bad internal ac convertion and regulation.