I have an 86 Toyota truck with charging system issue. Manual 5 speed transmission. It's got over 200k miles, still runs great(of coarse), but when removing the battery cable while running, it dies! I know there's not all that many components to the charging system so I can't figure out what's wrong. I've put three alternators on it, put a new ignition switch, re-wired from alternator to fuse box. Still not charging. Any suggestions would be greatly appreciated. I love this truck and want to heal it.
Have you had the alternator(s) tested offline to see if they're working? I wouldn't advise pulling battery cables off while the engine is running, though granted a 1986 model doesn't have the sophisticated electronics of more modern vehicles that can be damaged.
I bought the last alternator remanufactured so I assumed that Rock Auto tested it before they sold it to me.
Rock Auto doesn't test anything, the company is a jobber that has parts drop shipped from warehouses. They never see the parts. Many rebuilt alternators have notoriously bad quality and you cannot assume they're good.
What possible reason would you have for disconnecting the battery while the engine is running?
To check the alternator
The correct way to test the alternator is to connect your meter to the battery. At idle, it should be about 12.5 volts. If you rev it up, it should be about 14.5 volts. If you don't get these approximate readings, the alternator is bad.
At idle it should be more than that. 13V at least, but ideally more like 14V.
A fully charged battery is 12.7V, so 12.5V would mean that the battery is discharging.
AutoZone has a limited lifetime warranty alternator for $139.99 - Duralast Gold #14668N.
Correct Joe. I meant to say engine off 12.5 and idle 14.5 minimum. Thanks Joe.
does it have a separate voltage regulator or rectifier?
Have you tracked down an electrical schematic?
No separate regulator or rectifier. Schematic was no help.
well it might help us if you post it.
Scotty answers your question and explains what a terrible idea it is to disconnect the battery cable with the engine running.