Bricksters,
I have a 1980 242. Last week it crapped out on me at 2:30 am, on my way home from work in the middle of a snowstorm,OH,what a feeling!!! Anyway, It only has has 11.40 volts at the battery while running (should be 13.50, +or-), I replaced the brushes in the alternator one year ago, so I don't don't think it's the alternator, but it is 23 years old. So anyway, is it the alternator or voltage regulator? The battery is good, and the symptoms are that it just quit on me.

Why not troubleshoot first. You can determine if it is the Alternator or Volt. regulator by bypassing the voltage reg. The V/R supplies batt. voltage to the Field terminal (or Excite terminal) You shut eng. off. Disconnect the FLD. or EXC. wire from the back of the alternator. Put piece of tape over the wire end. You will be supplying batt. voltage to the FLD. terminal on the back of the Alternator with a jumper wire with alligator clips on the ends. You connect from the BAT. post terminal on the back of the Alternator to the FLD. spade terminal on the back of the Alternator. [DO NOT] have any accessories on as the voltage output of the Alternator (if working) will NOT be regulated, and if you rev. up the engine you will see that the un-regulated voltage can climb to 20-25 volts and higher very easily.
I usually start the eng. first, and let idle, then connect the jumper to the FLD. Terminal FIRST, and then touch the other end of the jumper to the BATT. term. If your Bat. is low, then there will be a spark when you touch the terminal, because it should immediately start to charge the Batt. BTW, don't allow your jumper lead to touch ANY ground surface. Look at your Digital Volt Meter and look for about 13.0 to 15.2. If you don't see that, then carefully rev. up the engine to 1000-1300 rpm and look at the V.O.M. If it doesn't charge then, the Alternator is not putting out. But it then could simply be the brushes, as others here have mentioned, so shut off eng. disconnect the jumper and pull the brush holder.
If however, it did put out 13v. minimum, then you now know it is the Voltage Regulator that is the culprit and you feel better about buying one, right ? Or you could at this point, buy a new brush holder that has the built-in V.Regulator and just tape up the old wires. HTH, Tom

Hi.

I recently had low charging on my 1990 244. I first traced all wires and tightend them up. turns out 3 connections were loose and or dirty. This however did'nt fix the problem. I then pulled out the alternator for inspection. It was pretty dirty, covered with road grime, salt and motor oil. (Car needs full gasket changes) All I did was clean the thing and noticed connections on the inside, that you can see through openings without taking it apart, were dirty, dry and slightly corroded. Cleaned them and put a dab of lubricant on all connections then reinstalled. Works fine now. Try tightening and cleaning before spending them bucks.

Hope this helps. (1980 242, 1982 242 GLT, 1990 244 DL)

i know it's already been said twice, but i have to say check the grounds. i had a similar problem a few weeks ago. same symptoms, figured it was the alternator. had it towed home, bought a POS rebuild, got started on the install and noticed the ground wire was off the back. put it back on and all is well.

good luck, and let us know how it turns out

I think on a 23-year old car I would take the path of least resistance, and just put in a rebuilt alternator or a known good one from a boneyard. Could be the brushes, could be the regulator, but the bearings are ancient at this point and a rebuilt is under $100. But DO check the wiring harness, the battery and ground connections, and definitely charge the battery before you start up with a replacement alt.

when under 12.. i think that pretty much means the alternator isn't doing anything.. make sure all the connections on the back or the alternator are good... check the groud and exciter connection. If either are loose... you won't be charging.

Kevin O'Brien
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1980 244DL, 1982 245GL, 1987 744GLE, 1991 245SE, 1996 855GLT, 2001 V70