92 F150 Charging/Short problems?
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92 F150 Charging/Short problems?
My dad's 92 F150 started acting up again on his way home from work yesterday and I hope you guys can help me figure out what to go looking at. When he started it up to head home from work yesterday morning he noticed that if he turned the lights or the heater on he'd see a big drop on his voltmeter in the dash (stock gauge). He limped it home, but last night when I went out to try and see what's going on, I tried to start it, but it was completely dead. Dome light barely glowed. Anyway, hooked up the jumper cables and got it started after a few minutes. Put the voltmeter on the battery and as long as the rpms were up a bit it'd show around 13.6, once the idle kicked down however, the volts would slowly drop. Increasing the rpms, the volts would slowly increase back up. We had almost this same problem a couple months ago and ended up replacing the battery and altenator. In retrospect I think the old battery was fine. The new altenator seemed to fix the problem at the time. Now though I'm thinking the problem lies somewhere else as the battery continued to drain while it was shutoff. Short somewhere? Or maybe it is something in the altenator?
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From: Virginia
Try the test below. If the light glows bright, take the wires off the alternator. If the light then goes out, then your alt is bad(blown diode or something). That would also explain the low voltage, though if the alt does not make the light go out, there are some other reasons why it would not be charging at low rpm. Let's start with the test below first, and see what you come up with.
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Thanks Dave. I had seen your diagram on a couple of the other posts I searched through and was on my list to check tonight. Which wires do I take off the altenator? If I remember correctly I think there are two plugs that clip into the alt., don't think there was anything else hooked up to it.
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HI Dave,
I tried the test with test light. When I tried like it's shown in your diagram the test light comes on and pulses. When I unplugged the wire harness to the alt. the light came on for a second and then quickly faded out and died. Tried it a few times and same result each time.
So I guess that means a bad alternator? This alternator is only a couple months old, so assuming this is the problem, could there something that causing the alternator to fail? Or might it just be a bum part to start with? Thanks again!
I tried the test with test light. When I tried like it's shown in your diagram the test light comes on and pulses. When I unplugged the wire harness to the alt. the light came on for a second and then quickly faded out and died. Tried it a few times and same result each time.
So I guess that means a bad alternator? This alternator is only a couple months old, so assuming this is the problem, could there something that causing the alternator to fail? Or might it just be a bum part to start with? Thanks again!
