Electrical Gremlins

2,315

Asked by Jun 18, 2017 at 03:35 PM about the 2000 Ford F-150 XLT Extended Cab SB

Question type: Maintenance & Repair

2000 F150 4.6L electrical gremlins! it started a couple of months ago going
down interstate.i had the A/C Heater blower motor on (just fresh air). i
looked at my charging hand and it was going upwards,not normal,cause i
eyeball gauges constantly.i turned the blower motor off and the gauge went
back to where it is supposed to be,i'm doing 70 mph and turned the blower
motor back on,then all panel lights came on and felt a JERK,turned blower
off again,all lights went off and seemed to be normal again,so i kept on
going on interstate. went 20 miles and checked voltage on battery
terminals>> 12.6 volts with truck off,14.22 with truck running? had an
Autozone Alternator on it when this happened,so i still had my factory
Motorcraft Alternator that went bad a few years ago,so i replaced the
regulator,stuck it on the truck(output is 14.22 vdc.NOW,it's doing the same
thing as the alternator i took off? when the hand does start moving up,i can
roll up the windows and when the windows reach the top(closed position)
the two switches (either one)makes a noise(buzzing/humming) noise and
all lights blink, gauges flicker,battery light comes on briefly and the
overhead outside temp lights cut off,then come back on? if i turn the blower
motor on,the charging hand goes up higher? it does not do this all the time.
i can ride around sometimes with the A/C full blast,and everything is
normal. i do have all speeds on the blower,so i am ASSUMING the resistor
is good? also sometimes the charging hand moves upwards with
NOTHING on except the engine running,not much, but does move up a
little and flickers or hand jumping just a little. i am lost and need help on this
one. also,i did take it to the ZONE and had the battery/alternator tested
with their hand held tester,and ZONER said all good? so i asked him to test
charging system again a few more times,then machine said bad regulator?
HELP! battery has never went dead or low enough to NOT crank the
engine,starts every time?

5 Answers

25,710

Sounds like you have a short being caused by vibration or arcing from a chaffed wire, also caused by vibration. Checking every wire will be tedious. Try disconnecting the power supply plug from the blower motor and see if the condition continues. If there is improvement the problem can be in the blower itself or the wiring associated with it. It's going to be a process of elimination.

2,315

Thanks. That is the first thing i thought of and like i said,it don't do it all the time,but i have yet to unplug the blower motor connector'like a big dummy! it may be that or drawing to much current(IDK)!! I am going to do that today and see what happens.the only other thing i can think of is that a guy replaced the bed and forgot to unplug the tag lights and had to splice the wires back,and didn't tell me(i just found that,so i will start at those two places).will update with findings..thanks,Steve

25,710

If the blower motor was bad or in the process of burning out it would pull more amperage, and in all probability, blow the associated fuse.

25,710

Also, check and clean the ground terminals. Check the one on the battery and follow the large ground wire off the battery who where it connects to the body/frame. If corrosion is present that could be your problem. Since the problem is intermittent, you can attach a secondary volt meter directly to the battery. Just make sure you get one which measures 8 to 16 volts and not 0 to 20. When the condition present's itself, and if you are in a safe location, simply pull over, leave the engine idle, and see if the secondary meter is acting the same (bouncing or fluctuating.)

2,315

ok,thanks...i will check this and get back to you with results...Steve

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