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87 ford f250 460 engine

I have resurrected a 87 ford f250 that had been sitting for a few years. changed the engine this year. Its about done but its not charging at least the red battery light comes on and the gauge is low. I had the alternator tested it was bad. So I got a used one for a junk yard. Same thing. Had that tested and it tested good tonight. The regulator is in the alternator, so I know that is good. I am going to clean up the connections, sure that wont do anything, check the wires and check the voltage on battery while running. What else can I check or do?

If you changed the engine, check for all grounds between the engine and chassis.

One ground that’s missed when an engine is changed on this vintage Ford is, between the back-side of the left cylinder head to the firewall.


If I remember right, this vintage alternator came with new connectors when you bought one from the parts store due to the connections getting burned up.

When what got burned up. I think you have me confused with someone else.

With the key in the ON position (engine not running) touch the alternator pulley with the tip of a screwdriver.
If you feel the magnetic attraction of the pulley then the alternator should be good.

You need to check the circuit between the alternator and battery positive terminal. I think there is a fusible link in that circuit. That’s the backyard version of testing.

I’d guess the problem is what OK mentions above, a problem with the fusible link connection between the alternator and the battery. Use a volt meter and measure the voltage between the alternator output post and the battery positive. Engine running. It shouldn’t measure over 0.3 volts except if the battery was almost completely dead and just starting to charge up again.

If I had that problem myself, first thing I obtain is the wiring diagram. On my Ford truck of early 70’s vintage, Ford changed the way the alternator circuit connected to the battery and the alternator warning light almost every single year from 1970 to 1979. Each year something was a little different for some reason. It may be the case your alternator isn’t exactly configured right for the way the truck wants it. Should be a fixable thing, but hard to know what to do without a wiring schematic. If you find an online schematic, post a link here and I’ll take a look.

It’s fixed. Was a broken wire inside the plastic close to the connector. Took ohm meter to find that. Easy fix. Yes it has a fusible link sealed. It reads 13.5 volts on battery at idle.

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Good job OP. Glad to hear the alternator’s producing juice again.

thanks, any more suggestions on the dodge neon with the check engine light on?