new alternator won't excite!
 

Patient: Evelyn 1983 240D


I've been reading all the various electrical threads, alternator threads etc. I understand that the alternator must be induced to begin to produce electricity. New alternator just installed, the old one (in retrospect) was probably fine.

The BATT light on the instrument cluster comes on with the key and I've swapped bulbs with the high beam socket, no change. I'm only getting 12.3 volts at the battery with the multimeter, and there is no discernible reduction in RPM's when the headlights are switched on. New battery, fully charged.

On a possibly related note, my glow plug light pretty much stays on all the time, as of a few days ago during the process of machining new threads into the ALT bracket etc. Sometimes it appears to cycle on and off, but the power lead coming into the GP relay gets pretty hot, sometimes causing the insulation on the wire to smoke. Needless to say I haven't let the engine run for any length of time.

This car must go back to her rightful owner by Thursday, I'm just trying to help out and am feeling the frustration. I am not very proficient at troubleshooting electrical systems so please write yr replies in crayon. Many thanks.

I would disable the glow circuit and recheck the voltage running. If the glow circuit is remaining on for example it takes a lot of power.
Your battery voltage while running may be reflecting that. Worth a check as it only takes a few minutes. Start the car and disable the glow circuit for the test. The feed wire getting hot enough to smoke is a pretty solid indication if you think about it.

sometimes I think just asking the question makes all the difference. I just went out and replaced the glow plugs and relay, and respliced the hot wire to the relay. Bingo. I'm showing 13.4V at the battery now. Definitely charging the battery. Also, my glow plug light is working as it should. Thanks.