Newbie alert!
Former chevy owner now the proud owner of a Red 1998 F150 Ext 3Door 5.4L. Just finished doing all the fluid changes and found lots of useful info here. Not brave enought to try the plugs yet!
My delimma is that if I park my truck for a week or so ( happens due to my employment) the battery drains down and is DOA. Ive had the battery tested, the alternator checked adn am perplexed. Bought the truck used from a small no name dealer so no warrenty. I did notice that I get the warning chime with the key out of the ignition and the headlights off with the driver door open. I tried the WD40 spray into the door latch without success. Any ideas? Maybe the door switch? Can it be tested (prefferably by me not the dealer)?

Thanks in advance!!!
Jon

PS- Is the new valve body for the tranny worth it and how much does it run? And what about the $270 KN filter Hi flo kit?

 

You say your headlights go off when you open the driver's door? If so, that sounds like you have a wire somewhere near your headlights crossed, or a wire where it should'nt be. Have you been wiring up foglights or something? Check all your wires from your headlight harness all the way back towards the rear of your truck. Ok, I just thought of something. Check your wires going into the doors that connect to your interior light. Sounds like one of the door switches is grounding out and shorting. And check your fuse box and make sure the correct fuses are in place, and all accessory wiring like radio power wires and ground wires are tight. It sure sounds like there is a short somewhere. It's just a matter of finding it.

 

Jonny,

Try disconnecting the positive terminal from the battery. Connect an ammeter to the positive bat terminal and the disconnected battery cable. With everything off (don't forget the underhood light) there should be no reading. If there is a reading, start pulling fuses until the reading vanishes. You've found the troublesome circuit.
Check that circuit for frayed wires, wet connections, the usual suspects. You'll usually find the problem...
If your truck is an XLT or better, it probably has a device that will shut off any electrical accessories left on, after about 40 minutes. That shouldn't be long enough to drain the bat.
Let us know what you find.

Slug

 

Does your truck have an alarm active?

 

Okay guys,

Truck is 100% stock and it does have the factory alarm system and is an XLT. None of the wiring has been screwed with the best I can tell. I plan to try the amp meter/fuse trick next time I'm home. I checked all the fuses and everything is stock according to the owners manual. The Haynes manual doesn't give much info on the fuse/electrical system.

I also thought the smart lagic would turn the accessories off after 40 minutes. Now that you mention it the radio and windows are supposed to stay on until the door is opened and last time I don't think they did.

Thanks for the leads guys, I'll keep you posted. Still torn on the Tranny valve body and or the improved intake.

Jon

 

have your PCM checked