Harley Gentry

My 1984 Ford F-150 (4x4)
300-Straight-6
Recently started having some seemingly large issues.

I've already replaced:
- Air Filter
- Fuel Filter
- Oil Filter
- Distributor Cap
- Spark Plugs / Wires
- Alternator
- Voltage Regulator
- Battery
- Headlights
- Tires

Now, the truck refuses to stay started and seems to be only running off the battery, the alternator was checked and it's good and hooked up right. But, when you unplug the battery after the truck is running the alternator should keep it running.. It does not.

The headlights also act like a killswitch, you pull them on and the truck cuts off.

I don't know what else to do and I have FIVE days to get it fixed and sold so I can move to California... ANY SUGGESTIONS?

Manuellabour247

the only thing I can think of is that you have a short in your harness. Look for any signs of excess heat on the uncovered wiring. Also check that all of your grounds are properly connected. (body to engine to battery, etc). You are correct that the truck should stay running after you disconnect the battery. However, you have to slightly rev your engine above 1200 RPM for most Alternators to start the charging cycle. Just idling will not charge the system.

Harley Gentry

I'll be sure to check all that, my truck actually stalls while I'm driving lol It's such a pain. (I have to jump it off all the time, and since it only is running off the batter... It doesn't stay running but maybe ten-fifteen minutes.

Manuellabour247

Other than the ground, I would trace the wires coming off of your alternator to the battery and coil. Then go from there. Sounds like your alternator isn't able to do it's job. And the light switch thing may fust be a spike in energy to turn your lights on killing any spark to your coil. My truck did that when I was running on the battery after a belt broke.

fordsadist

I had very similar issue in a ranger p/u and it turned out to be of all things the idiot light circuit! there is a 500 ohm resistor on the back side of cluster that if it isn't in the circuit the charging system WILL NOT function! if someone has changed the cluster to one with a gauge and the alternator wasn't changed to one for a gauge it wont charge.I had that issue and i made a little box with a 194 bulb and a 500 ohm resistor and wired it in with the regulator and then everything worked great!

1967 Tempest

If you have a limited time, you can switch temporarily to a 1 wire alternator. Yes, there is a 1 wire 3 wire discussion et al. But if the alternator is not charging the battery and you need a quick fix, this would work.

The alternator I linked below is for a 100A 1-wire alternator. You hook the back charging wire from the alternator directly to the + side of the battery and you are done.

That said, the gauges directly attached to charging system may not function. Voltmeter or ammeter if equipped, as these might get bypassed from the 1-wire. BUT, this will solve your issue if infact it is an issue with the regulator or dash as previously stated.

A great price at $91.97.
Dave

http://www.summitracing.com/parts/su...-150/year/1984

Manuellabour247

^^^
X2. I forgot about the 1-wire alternator. I know in Kansas these are for "agricultural" use when on the roadway, but I know a lot of people that use them in an older rig. But 1967 Tempest is correct in saying it would be a temporary fix that could help you isolate the issue. Other places you might try are Oreilly's/AutoZone/etc. They might be able to do a little better on the price.