F-150 battery drain

Asked by May 09, 2017 at 01:46 PM about the 2000 Ford F-150 Work 4WD Extended Cab LB

Question type: Maintenance & Repair

My 2000 F-150 has had 2 new batteries in
the last 3 months.  Parasitic drain Is
certain.  My amp meter fluctuates between
.05 and .01 amp.  I disconnect the negative
battery terminal and the cluster relay #2 in
the cab fuse panel alternates on and off.  
To my knowledge nothing is being
activated.  KOEO.  Brought the alternator
in to have it checked.  They put new
regulator in it.  Problem is still there.  
Battery dropped from full charge 12.8V to
11V in 24 hrs.  Anybody have ideas? We

6 Answers

Could be anything

118,755

forget the meter, put a test light in between the battery post and cable end, if the light turns on bright then you have enough of a draw to kill a battery in a short period of time, first electrically disconnect the alternator, if the light goes out or drops to just a faint glow you have found your problem, most likely a failing diode in the alternator, if the light stays on bright then start removing the fuses one at a time noting where each one goes until the light goes out, when it finally does then find out what is on that circuit and replace or repair the circuit or component, then start putting the fuses back one at a time watching the light just in case there was one that was missed, when all the fuses are back in and the light is still off or just a faint glow then reconnect the alternator, if the light is still off or glowing faintly then your done, reconnect the battery. Note parasitic draws only cause a lamp to just glow slightly and they will not kill a good battery in a short period of time, but they can eventually, but it can take weeks or even months to do so. A really good battery should have at least 13.2 volts sitting with no load on it fully charged, but again that is a really good one.

1 people found this helpful.

Ok! Gotcha I'll check that out and get back. The #2 relay (instrument cluster) I think is being fed juice from a previous auto start that was remove (probably didn't work and was badly connected). But I'll do the sequence of checks as you described. Thanks Tennisshoes :-)

Well I disconnected the alternator and still get that blinking relay #2 under the dash. I got rid of all the remote starter wiring and rechecked. Same same. Then I pulled one plug at a time under the dash and still same same. Even unbolted harness to steering column and no change. I'm starting to wonder if this cluster relay is supposed to be on all the time? I switched with #1 relay and no difference. However that position #1 only has juice with door open switch. So I still can't isolate the problem yet with #2 cluster relay. If it is supposed to be on all the time then I have a circuit that draws too much current somewhere in the cluster gauges etc. Not having a diagram makes this difficult. Any suggestions please?

118,755

Then I'm thinking you may have a crosscircuit somewhere in that number two relay circuit, I would try your local library in the reference section for a shop manual, and have the wiring diagrams copied for you, that would be the cheapest route on finding diagrams.

In case you're interested I disconnected and reconnected every darn thing I could lay my hands on under the dash and...it works. No drain and everything works. Go figure. Just hope it lasts...

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