I have a 2002 F150 SuperCrew with the FX4 package. We recently had a really heavy snow storm here in Denver (over 3 feet in a day and a half in the city) and ever since I have been hearing this intermittent buzzer sounding from under the dash. It is odd because all of the other sounds the vehicle makes are chimes of one kind or another. This is clearly a piezo-like old fashioned buzzer (which I might add is very annoying).

It first started when I drove the truck after digging it out of the parking space and driving a few miles across town. Note that at this point, I had not driven through any heavy snow accumulations yet. About a mile into the trip, the buzzer started buzzing continually. It would stop whenever I tapped the brakes (it was clearly tied to the brake light switch in some way) and then resume as soon as I let my foot off. Unfortunately, at this time I did not try to track down where the buzz was coming from. It continued this constant buzz for the next few times I drove it and then stopped, mostly. It has now been a couple of weeks and the buzzer starts up every now and then for a couple of seconds (usually in response to a bump or sudden stop, etc). Since it only buzzes sometimes when I am driving, I have no chance of finding this buzzer and disconnecting it.

I would really like to know the cause, though. Any clues? Some people have suggested that it could be some kind of flood sensor that got messed up by excessive snow (I find this unlikely) or something related to the towing package. In any case, something is not right. I would be more than happy to disconnect this buzzer (if I can find it) like I have disconnected the various chimes, but I am worried that something is wrong and would like to address the root problem.

 

Hi tlaurenzo and welcome to FTE

Can you get it to do it if you bang, push, pull wiring etc under the dash? I'm thinking that maybe you got a relay wet or something and it is partially engaging. There arent too many things tied into the brake light circuit though but one thing is the shift lock actuator which is a solenoid. Solenoids can buzz if they have a bit of power going to them but not enough to pull in the plunger. You could maybe try unplugging the shift lock and see what happens. To get the truck in gear you'll have to have the ignition in the off position but not in lock and then move the shifter to neutral and go from there. With the engine running you wont be able to get it out of park.
Let us know if you find anything

 

I will check around, but I have so far been unable to get it to happen "on demand". Also, I have never heard a seolenoid buzz like this. This is not a quiet buzz. Remember the buzzers on cars in the 70s and 80s for when you left your key in the ignition (before they started using electronic chimes)? That is what this is... It is loud and very "nasal". There is no doubt in my mind that it is a warning buzzer and not just a bad component.

I almost think that if it is a short or wet circuit, it has to be something outside of the cab. When this started, all the truck had been doing was sitting outside with no activity (my towing/plowing/getting stuck adventures all took place after the buzzer started)... It wasn't even exceptionally cold (no lower than 25 or so). Being brand new, I doubt that the cab is too leaky yet and I did not notice any wetness inside.

The truck has the standard towing package from Ford, complete with electrical hookups for a trailer. I don't know any particulars about this, but I figure that this is one of the few circuits which would be hooked into the brake switch (aside from the shift interlock which I will check into). Also, a substantial portion of these circuits are outside and exposed (at least compared to the relative protection of the cab). Is there any kind of warning buzzer related to the towing hookups? It wouldn't be too hard to imaging that some snow, water or ice got into the tow hookup and caused it to appear as though non-existent trailer lights or brakes were malfunctioning.

Since the buzzer has mostly stopped, I wouldn't be too concerned except that no one seems to believe that there is such a buzzer. It is either a terribly malfunctioning component or something that no one has really encountered before (at least of those I have talked to). In any case, it is more of a mystery now than a problem.

 

I dont think Ford has used an actual buzzer in a vehicle in ages. They all have the dingdong type warning thing.
A relay or solenoid can buzz though so I think that's where I'd be looking. There are a few relays under the dash, in the GEM etc. Unfortunately if you can't get it to do it you're going to have a hard time finding the cause.

 

It's a solenoid or control module of some sort. You may want to check with your dealer, because I seem to recall there was a TSB on this a few years ago, applied mostly to '97-'99s. I doubt the TSB still applies to your '03, but it should help in finding the problem. Racerguy is on the right track: some snow/ moisture probably got in through the heater vent, and this "buzzing" item is probably near these vents.

 

I would look into the shift interlock. I have heard these buzz terribly before in other brands of vehicles because something is wrong. I would discount it happening at the snowstorm as coincidence.

The fact that it will diminish when you step on the brake would indicate that its definitely the shift interlock. Have you noticed that the interlock works normally (can't shift from park with ignition in run position?). I believe that its electrically activated, but normally off, which is why you can shift the truck in the unlock but not the run position. Stepping on the brake deactivates the interlock, so therefore stopping the noise.

Chris