OK folks, I'm new here so please bare with me. My wife and I both own '99 F150's. Hers a supercab XLT 4.6, mine a regular cab XL 4.6. My wife's truck is having some electrical problems. She's having intermittent problems with her power door locks, her ABS light, and her airbag lights.First, her door locks.There are times the locks work perfectly, then there are times they are "weak." I read in another thread about the relay going bad.I'm not sold on that yet.Second, her ABS light. The light will come on for as long as a day and then go out.Brakes are working fine at all times.And third, her air bag lights. She has the passenger bag turned off when my children are in the truck.The "off" light does not come on in the dash.Also the air bag light on the dash will come on and stay on for a couple of days and then go out.My father-in-law (a pretty dang good mechanic) swears it's one of the many grounds under the hood.My wife and I spent a couple of hours one saturday and removed each ground that we could find under the hood and made sure we had a clean gounding area.A day or two later all the problems disappeared, and everything worked fine.Now after 4 months the same problems are back.Any ideas?Sorry about the long thread, but I didn't want to leave anything out.Thanks
Gene

 

check your fuse box , is the fuse loose , are the terminals making a tight fit.

 

My ABS does that too. I have 1995. Doesn't happen frequently, but I do have the same symptoms. The guys at the garage say that my ABS system needs fixed. Not sure why but I know it can't be cheap so I'm just ignoring it for now.

 

Before just throwing parts at any repair, I highly suggest taking it to a ford dealer, and seeing if any codes, for the abs, and other systems are in there.
Your door lock problems are more then likely the actuators taking (or getting ready), to take a dump. Have replaced plenty of them for intermittent slow/sticky operation.
As far as your Air bag light not coming on when you switch the dash switch, it's usually that part. (the switch part), that goes bad. Quite common, actually.
Again, if you had the codes read for the air bag system, it'd show a code for internal failure of the resistor, and/or switching part of that setup. (dash switch).

Lots of problems from water intrusion, and customers, (whomever), tinkering (i.e. adding on electrical accessories), basically bastardizing the fuse panel by NOT using the proper connections, just basicallly stuffing wires alongside the fuses, and trashing the connections for both the fuse, and their accessories.
Have it diagnosed. SAve you lots of time/trouble/headaches in the long run.............My .002