Hello I have a 2002 f150 4.6l. My battery won't stay charged. The truck starts and drives great but if I don't start it for 3-7 days then my battery is totally dead and I can't seem to figure it out. This has been happening for about 6 months and I'm getting ready to change out my blower motor as it doesn't work anymore and I'm wondering if that's draining my battery not sure i have all lights turned off as well any help is appreciated thanks.

 

You can't throw parts at a problem, you have to know what the problem is. 1st place to start is have the battery load tested. Actually, disconnect the battery when you last drive it and know you won't drive it for a few days. When you reconnect the battery (ground) if it starts fine after setting for a week or so, you know you have a parasitic (or more) load on it when it's connected. If it doesn't start or starts weak, you know it's the battery. I personally doubt that it's the blower motor. Have someone put an amp clamp on the negative cable when it's setting with nothing on. It shouldn't show more than .2 amp draw with doors closed and NOTHING on, possibly as low as .05 A. (50 milliamp)

 

Yea one thing I never do is throw parts at a vehicle I've worked on lots of cars just never had an issue like this before and since my blower just makes a humming sound and not working I have to fix it. Ill try wht you said to see if it works thanks.

 

Also every time I get a new battery ill run the truck for 20 mins or so to make sure it's fully charged and if I don't start it for 5 days it's dead.

 

Ok got a new battery in my truck now do I did pulled all fuses and checked and came up with the problem fuse my draw amps before I pulled the fuse was .23 and after I pulled the #15 fuse it dropped to .02-.04amp. The #15 fuse is a 5amp stop light switch (speed control, brake shift interlock) GEN, RABS module. So it's got to be one of those as the manual says that's what the fuse is for but what do I do to check out those to find the problem that needs to be fixed I'm not the good with electrical stuff. Any help is greatly appreciated thanks

 

When you were testing, did you open and close the doors ?
- If so, the battery saver time delay started over and the draw is higher at this time.


BTW : if you are not driving the truck, put it on a battery maintainer to keep it charged. Idle for 20 min is not going to do as well ( if anything ) to a battery that is getting drawn down. the alternator is meant to charge a good battery, not a low battery.

 

Yea I had the door open but ill recheck the fuses again on Tuesday and ill repost the info. Can't believe I forgot the door was open I hate messing with electric stuff. Thanks for the help.

 

GF- I doubt that the .23 A draw is your problem, that's not really excessive. As Steve said, gotta make sure there is NO draw from anything being on (doors closed and nothing on time delay or booting up). Pop the hood and make sure that any underhood light is removed and the doors are closed and come back 15 min. later and do the amp clamp on the ground cable. If you use a Fuse Buddy on individual fuses you'll find that the small initial draw will often taper to nothing or almost nothing as the time delay or reboot draw is satisfied. If your concerned about the fan motor, just pull the plug off the rheostat for the fan motor, it's easy to get to. If you DISCONNECT the ground to use a DVM when you put the DVM inline it will start those draws over again. IF you are disconnecting, you have to connect one probe to the cable end and put the other down through the end as it is seperated from the post to eliminate that problem. You can do the same thing with a test light and with a little experience tell from the intensity of the test light about how much draw there is. Eliminates the bumping up from a disconnect.