More or less suddenly my truck has developed several electrical problems. The truck starts and runs fine. Battery voltage is (12.5V engine off), 13.7V (engine running). Here are the problems.

1. Weak electric door locks. Both door locks got weak at the same time.

2. Sometimes the speedometer doesn't work. When this happens the "off" lamp on the "overdrive" on/off switch (on the end of the shift ****) starts blinking. Turn the engine off, restart, problem goes away. This happens about 1 time out of 5 that I run the truck.

3. The ABS light comes on when the vehicle starts moving, and stays on. This always happens.

The "Check Engine" light was on. Took it to Autozone and the guy read the computer. It said "speed sensor". A guy on "Just Answer.com" told me to replace the speed sensor located on the rear differential. I found that and unplugged it. All problems still the same. The speedometer even works most of the time. What kinda speed sensor is this thing if the speedometer works with it unplugged? I would go ahead and replace this thing if I saw it making any difference when I disconnected it. I disconnected the battery and cleaned the terminals. They were a bit funky looking. "Check Engine" light is now off.

The "justanswer.com" guy also said to replace the door lock actuators, but didn't give me enough info to actually do it. I read on this forum about the weak door locks on Excursions and such and that the original actuators we a POS, and how some people rebuilt them by shorting out a 3-5 ohm resistor inside. Also the guy on this forum really gave good info on how to do the job. (https://www.ford-trucks.com/forums/5...ch-folder.html)

Here's what I think... the reason the resistor in the door lock actuator is a problem is that there is a dirty or corroded 12V power connection somewhere. That puts some additional resistance in series with the door lock actuator. I think this bad connection is also goofing up my speedometer and the ABS system. Or maybe not. Maybe both door locks, the speedometer, and the ABS system all went bad at the same time.

I checked all fuses, reseated them, reseated all relays on the fuse blocks. No help.

I'm stumped.

 

Just change the $12 speed sensor it will clear everything except the door lock,a seperate problem I would believe.By the way,nappa calls them A.B.S. sensors.

 

Thanks dryfly. I will do that.
If I could figure out where the connectors were that brought power to the door locks I would reseat them.

 

your welcome.But thanks to all the veteran folks on this forum,I'm kinda new here also and these guys set me straight on quite a few problems on my truck.To include that one.So good luck and welcome to the best forum on the net.

 

The battery voltage running should be 14,5 volts or close 13.7 isn't enough if you check it after a drive when the battery is fully charged. The speed sensors do get changed quite often.


Dick

 

Thanks 99f350sd. So if the charging voltage is low, then is the problem the alternator, regulator, or battery? Low voltage would explain why the window locks don't work right.

 

Door locks should work good at 12.5 volts. Check charging system with fully charged battery. I think mine is 14.7 I have a special regulator for high output for winch ,plow etc..Stock reg is 14.5 volts. Normally you don't have to rev the engine. Regulator is inside the alt. Easy to change it and brushes.


Dick

 

I was experiencing slow windows, locks, all the indicator lights going crazy pretty much all that you described also. I found the rectangle plug that has a bolt through it that goes through the firewall and into the GEM [generic electronic module] aka aluminum computer box was loose. I could be traveling and hit a bump or a jar to the truck and all of these crazy things would happen. This sounds so simple to be true but it corrected my problem and got me back on the road. Getting to this bolt is tough. It is under the master cylinder at the fire wall. Mine was very loose causing bad connections to every function of my truck. I think that it is like a #10 metric socket 1/4" rachet.
Good Luck