Strange electrical puzzle

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Sep 20, 2014 | 11:44 AM

RickardC

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Strange electrical puzzle

1980 F-250, 351M. Battery tests OK - 500 cold cranking amps. New starter, new starter solenoid. When I turn the key to ignition, small click under the hood on driver's side. Turn to start, the starter solenoid clicks once, but no turnover. After that, all electrical is dead - no lights, no horn, no radio, no clicks. Turn the key to accessory, gauges work, but no radio, etc. Turn the key to ignition, nothing.

Tried jumping from another car, and the cables melted. I'm baffled. Can you help?

Sep 20, 2014 | 03:12 PM

Franklin2

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From: Virginia

Sounds like a bad cable. Where they melted might be the bad spot. Do you have a meter and know how to use it? If so, we can walk you through testing to find the bad spot. But you will more than likely need someone to help you. You can't do any testing except under load, so that means someone turning the key to start while you hold the meter leads under the hood and watch the meter.

Sep 24, 2014 | 08:47 AM

RickardC

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The cable that melted the insulation was the jumper cable - not one of the battery cables. Regarding a meter - do you mean an ammeter? I have a multi-meter that will only read up to 250 milliamps. I presume you mean one that reads higher? If so, what do you recommend?

Sep 24, 2014 | 10:52 AM

Franklin2

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You can use a multi-meter. The first thing to do is put the meter on a scale to read 12v, and put the meter on the battery posts(everything is connected up as normal as far as wiring). You should get around 12v on the meter. While you are holding the meter on the posts, get someone to crank it. When it clicks, if the voltage drops way down to almost nothing, then you have battery problem.

If that stayed around 12v or so, keep your meter negative lead on the battery neg post, but move the + lead to the solenoid post where the battery cable hooks to. Keep holding it while someone tries to crank it. When it clicks, if the voltage drops way down, then you are losing it in that short positive cable.

If that checks out ok, you can leave the + lead where you have it, but take the neg lead off the neg battery post and put it on a clean metal spot on the engine. While holding the meter leads again, get someone to try and crank it. If you lose it, then your neg battery cable is bad.

See how this works? Your meter is no good just poking around checking for voltages UNLESS you check for voltage when there is a load on the circuit.

Oct 3, 2014 | 09:00 AM

RickardC

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Ignition switch

Since gauges respond intermittenly to ignition switch position (sometimes on, sometimes off, when in acc or on) - could it be the ignition switch?

Oct 3, 2014 | 11:47 AM

Franklin2

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If you want to bypass the ignition switch and see if it's a problem, look at the diagram below. Take a short small piece of wire and touch one end to point #3, and as soon as you touch the other end to point #5, the solenoid should click and it should turn over.

Oct 5, 2014 | 05:53 PM

RickardC

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Solenoid clicked, but the starter did not engage. Took it out, tested it - bad, even though it was new. Traded it in for a new one, put it on, and got some solenoid clicking for a while, but after a minute, jumper cables heated up, started smoking. New starter now fried. Took it off, connected it directly to a battery that was out of the truck - cables heated up, no rotation. Any ideas?