Hi all, I'm new here and trying this forum as a next to last resort. I'm a handy DIYer only.

My mother-in-law has kept my deceased father-in-law's 2000 Ranger since he died about 10 years ago - it sits most of the time though she drives in a couple of times a month. My wife recently borrowed it when her car was being repaired at the body shop (a whole other issue...)

Anyhow, she drove it for a few days before it suddenly stopped while she was driving home from work. She called me thinking it was out of gas (an issue tied to the body shop issue above, but I digress). I headed out with a gas container in what was remnants of Hurricane Ian, so pretty much getting pelted with hard rain and wind. Added gas, but the truck would not start, thinking it was low battery from flashing lights, I went to jump start the battery. Here's the first key piece of data - when jump starting the truck in the hurricane, I inadvertently switched polarity, but noticed it within seconds and fixed it. The truck started but within seconds after removing the cables, it died. Went and bought a new battery thinking it was likely time. Changed the battery, again, no fun in a hurricane, the truck started and we drove home - about 25 miles. Approximately 1 mile from the house, truck died again.

After getting it home the next day, I went to AutoZone and bought a new alternator. Jumped and then slowly died after removing the life support cables. Called a friend who said that aftermarket alternators are mostly junk, so I took the alternator back and eventually ended up buying one directly from Ford. Changed it out, same result. I tested the continuity (B+ to positive terminal on my multimeter and there appears to be continuity (0 volts). When running after the Ford alternator installed, I put the meter on the battery and watched the volts slowly fall to 6 and the truck sputtered to a halt again.

I found 1 blown fuse in the cabin compartment that appears tied to the radio. Haven't replaced it yet, but didn't think it was a big deal with the above issue. When I look at the owners manual and a few resources on line, the only other thing I could find related to the alternator was the alternator voltage regulator which was a relay in the engine fuse box. Replaced it with no change in outcome.

So, I'm guessing the alternator is good. Is there another fuse that I'm missing? Some kind of inline fuse? If so, where would I gain access to it? Any additional thoughts? Or, should I take it to a pro?

Any and all help appreciated!!!!
Thanks!

 

Welcome to the forum

2000 charging system diagram below

Yes there are 3 fuses and reversing polarity could have blown 1 or 2

With all wires hooked up and Key OFF
On the outside of engine fuse box is the Mega fuse
Set Volt meter to DC volts
Test Battery volts, 12.3v to 12.9v is normal, under 12.3v is a drained battery, REMEMBER THIS VOLTAGE

Leave volt meters black probe on Battery Negative
Use the Red probe to test Mega fuse's 2 terminals, should see "battery volts" on each terminal, if not replace that Mega Fuse
"Battery Volts" is why you test the battery first, you need that number for comparision

If Mega fuse is OK
Open engine fuse box and check ALT SYS fuse, 30amp, replace if blown

If its OK, turn on the key, engine off
Battery Light on the dash should come on, if not then Cab Fuse box fuse 15 is blown, 7.5amp, replace it

Once all have been tested, start the engine
Test battery voltage again, should see 13.5v to14.8volts, this is the alternator working
Under 13.5v means alternator is NOT working


Battery's sole purpose in a vehicle is to START THE ENGINE, its maximum voltage is 13.0v brand new, usually 12.8v
Once engine starts, EVERYTHING electrical is powered by the alternator, its minimum voltage is 13.5v so voltage travels TO the battery to keep it charged up for the next time you need to start the engine

If alternator is not working OR its power can't flow to the vehicle(blown fuses), then the computer, fuel pump, spark system, fan, lights will ALL be running off Battery Voltage, and it won't last long, not what its made for, its designed to work at high amps for 10 seconds maybe, at a time to start the engine
So computer stops, fuel pump stops, and...........engine stops when battery is drained to low

 

Thanks RonD!

I worked all around that mega fuse and never thought to pop open that plastic cover.
One side of the fuse matched the battery voltage, the other, not so much. Ordered and awaiting shipment. Will update if I get it moving. Thanks again!