Question about 1990 Ford F150
I have a 1990 ford f150 with a 4.6 6 cyl.. Went to start it and nothing, jumped it got it started. Ok, thought battery was bad (at least that was what I was told) so got new battery. Drove it home, it set a couple of days, went to start it, yep, battery dead. Had alt. cheched out it's ok, even had wire tested from selinoid to alt., it's ok, had starter checked out, it's ok. What could be causing the battery to be drained? I had noticed at times when I tried to start it before that it would grunt at times. I'm at witts end here.
The diode inside the alternator is getting weak. The charging system is for a direct current as you may know (DC) when a diode gets weak or goes completely dead the charging system is conveted to an alternating current same as your house current works. When a vehicle charging system looses its DC current the battery will not charge through the alternator. To check and see if your alternator has a faulty diode do this with the ENGINE RUNNING. Take a volt meter with its setting on the DC MODE and touch the probes to the corect terminals of the battery. You should get a reading of voltage. Remember the reading as displayed. Now Remove the probes and switch the setting to AC mode then reverse the probes + to Negative & - to the Positive. If the readings display the same your diode is shot
Posted on Jul 11, 2010
You need to pull fuses to see,but it can still be the alternator,with a bad diode allowing the drain,remove the negative battery cable from the battery,then buy a test light,they are cheap,clip one end to the negative battery cable,and touch the tip of the test light to the battery post,and the test light will light up,cause there is a draw on the system,make sure the doors are shut,and the lights are off.Then unplug the connector on the alternator,if the test light light goes off,the alternator is the problem,if not,remove the dome light fuse,and start pulling fuses one,at a time,and putting them back in,as you go,if you pull a fuse,and the test light light goes out,that is the circuit that is drawing the voltage from the battery,leave it out,and hook cable back up,and see what does not work with the fuse still out,and that will be the problem,please rate if this was at all helpful,thank you.
Posted on Jul 11, 2010
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Posted on Jan 02, 2017
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