I have a '99 F350 4x4 with 7.3L and auto. Whenever I'm on the highway and hit 75, the door dinger goes off (same chime as key in the ignition and door open). The chime goes off when I go back below 73.

Ideas?

Thoughts I had were: some kind of 4x4 overspeed sensor (didn't see one on the front diff..), aftermarket device installed for work crew, and malfunctioning multi-function switch.

Has anyone else had this problem?

 

Could be reason that you shouldn't drive above 70 mph on highway

 

Your truck might be trying to tell you there is something wrong with the Air Bag/SRS system.

 

Now how do you figure? The truck has an Air Bag light...which isn't on btw... so why the Air Bag? SRS? Seat belts? There is a light for that too.. I'm open to any suggestions, but with no idiot lights where do I start?

 

I would guess that the airflow over the cab is pulling outward on the doors at speed and the switch is being activated.
Adjusting the door striker to hold the door a bit tighter closed should fix the problem.

 

Or spray the door latch ***'by with WD40. Do you also get the "DOOR AJAR" message?

 

my 99 at work does it also has since new

 

Ok, now we're getting somewhere. Your '99 at work has done it since it was new. Is it a 4 Wheel drive model? AUTO? Diesel?

It seems electronic to me... if it was air flow or door locks it should have some intermittant changes in behavior, but it ONLY comes on when the truck is at exactly 75 on the speedo and subsequently does not go off until exactly 73 every single time. I wonder if that is something that Ford can turn on and off.

 

Called the Ford guys, the service guy says "no overspeed switch on the 4x4" and he suggested possibly the door switch (I have a date with some WD-40) and possibly the ignition module is grounding out somewhere. He also said to check the "pins" which sounded vague enough to be completely incomprehensible to the layman.

 

are you wearing your seat belt?

I used to work for a company that used all econolines I noticed the same alarm...I was never able to determine if it was because my assistant never wore a seat belt or if it was just a reminder to check your speed.

 

I always wear mine, no dash lights, even when the alarm is going off. It seems to be a ghost problem, but a common one.

 

My brother in laws F350 had a rear door triggering the door ajar signal and light. He tried the WD 40 deal with no result. Would not quite beeping on our deer hunt this year, so when we got back he tore into the door and found a hole rubbed through the insulation of one of the wires. Taped it up and it is fixed after progressivly getting worse over 2 years

 

my dad's truck does that

it's a F250 with the 7.3, i think its the super cab, one with the suicide doors, does it at 73 and goes off at 71, we still don't know what's causing it,

 

Supposedly, our trucks have a speed limiter. I've never gone fast enough to tell (my speedo's five slow @ 65) what happens, but if I'm right, our trucks have limiters at 80mph. I wonder if it's just telling you to slow down? I've also heard from a friend they're gonna raise the speed limit to 75 on the interstates over here sometime this year! Does that mean everbody's gonna have dinging Super-Duties? Supposedly, I can remove the speed limiter with my Superchips, but my truck's at the stock setting right now. So, I'm curious to see where this goes.

 

The speed limiter does not have an audible alarm. The vehicle simply will not continue to accelerate. And yes the Superchips programmer has the ability to disable the limiter.