Ford F-250 back up alarm

[frhrwa]

does anyone know the wiring or set up for the back up alarm on the super duty, 2002 Ford? mine works intermittently.. the light stays on most of the time and I can't enable it.. then all of a sudden it works for a few days? what do I check and where? thanks.. wayne

[dacflyer]

i'd suspect a loose ground wire or corroded terminal.

[gerty]

I agree with dacflyer.. Most people hate listening to those things and disconnect them. Check for any cut wires that have been twisted back together and not protected from the elements.The backup alarm should come on when your backup lights do. If the lights come on, but not the alarm, the problem should be right there at the back of the truck. If no light and no alarm the problem could be on the shift indicator switch, bad power connection, bad wire connection anywhere in between..
Let us know what you find..

[Ed B.]

frhrwa

Go to Rat Shack and buy a "PIEZO BUZZER" - 12 volt or better-and connect it (1) to the wire going to the 'back-up (White) light and (2) the other wire to a good ground. Mount the buzzer with epoxy glue somewhere on a rear quarter panel (at the rear of the truck).
When the white back-up light comes on so will the buzzer. We did this on our church school bus and it worked like a charm.
You could probably do better from a mail order company but then you would be paying 5 to 6 bucks for shipping.
Good Luck.

Ed B.

[frhrwa]

actually, this isn't a back up alarm, its an alarm to let you know when someone is behind you... if a person or car, tree, cement post, etc is there it sounds an alarm.. but only intermittent... has a reset button to push if you have a trailer back there... only when its not working, that reset stays on... has been working for the past 3 days, so... I'll get under and check for a bad connection today..

[dacflyer]

oh, your talking about them ultrasonic sensors, theres usually 4 mounted in the bumper, they look like buttons,
its a distance warning system, its possible that one of your sensors might be going bad, i havve no idea how you would test the sensors out.

good luck,

[haklesup]

The way that is supposed to work is that the system is enabled when you turn the car on and you can disable it by pushing the button which also lights its indicator reminding you it is disabled. Powering the car off and on again should re-enable the system

From your description, it sounds like the button on the dash is stuck in the pushed (closed) state. Even if the surface of the button is popped out, the contacts or button internals may still be sticking or broken. I have this problem on one of my window switches and it seems to be caused by coca cola. These switches are often located close to the cup holder. Vigorous poking of the switch always restores operation in my case.

Try excercising the switch vigorously by rapidly pressing it a bunch of times. Maybe you can confirm the switch function by getting to the wires with an ohmmeter. I expect it to be a momentary normally open switch but it may be NC.

I'd definately start at the switch as it is the only moving user accessible part of the system. If that checks out, a dealer may be able to read out a failure code.

then all of a sudden it works for a few days?

Does it stop working when you decide to try the disable button to see what happens?

[frhrwa]

nope.. it just suddenly starts working.. I've pressed the button like a machine gun just in case that was the problem, but it didn't work, the light would go out and come back on when you released it. It could be the button contacts tho, will see how accessable the switch is, just hoped someone had a wiring diagram like you used to be able to get in Chiltons and Motor Manual.. then I could trace it out, or at least see the trail of failure.. thanks.. wa

[haklesup]

I observed on mine that the lamp comes on for a moment when I start the car just like all the other idiot lights on the dash. This implies that it does a self test and like any of the other indicators, would stay lit if there was a problem.

So, it could be anything. Still, call the dealer service department and see if that is wired to the car's computer in which case, can a failure code be read out. They might even offer up what they know to be the most common cause of trouble. Have you asked on usenet newsgroups better tuned to automotive subjects? Service manuals are available for most cars and if you get the factory one (not Chiltons) you will get the schematics you want as well as wire harness reference designators wire colors and physical location.

Found two on ebay, heres one

http://cgi.ebay.com/FORD-F150-F250-SERV ... dZViewItem