1987 245 Alternator not charging.

waynej · Post by **waynej** » 01 Mar 2009, 17:17

All the lights across the bottom of instrument panel came on, battery started getting weak. Put the meter on and alternator is not charging. Charged the battery overnight and started checking things.Disconnected wire from instrument panel to D+ on alternator.
Connected test light to D+, when I put 12V to other side of test light alt. starts charging and continues charging when light is removed.Tried grounding wire from inst panel through test light-nothing happens- all lights stay on.Tried grounding panel wire directly to ground-nothing. Tried 12V through test light to panel wire-nothing.
Does anyone have any idea what the problem is?
Thanks,

drsugg · Post by **drsugg** » 01 Mar 2009, 19:05

Sounds like the alternator itself is working. I'm a little confused on your test lamp checks. Test should be; Pull small wire from alt, dash lamps go out, ground wire, lamps go on. The wire harness is the usual problem on this car.If dash lamps are on with small wire off alt, the fault is USUALLY, the wire harness under the crank pulley. Disconnect battery, disconnect wires from alt and oil pressure switch, from under the car, pull wire harness down from between alt and block. Notice that the wire harness is attached under crank pulley by two bendable metal strips,unbend and pull harness down. Cut open shrink tube to expose the wires and you should find your problem.

waynej · Post by **waynej** » 04 Mar 2009, 20:32

Thanks drsugg, i was afraid it might be the harness, but was hoping for something simpler. I guess these alternators have some residual magnetism when they get old. I left the little red wire off and the alternator starts charging when the engine RPM gets up to about 2500 and continues charging at all speeds until the next time the engine stops. The car is very drivable until I get time to fix the harness.