1993 500E - Alternator Output

[charnett]

Is there an easy means by which to check alternator output with a a $39 type of multi-tester? If the procedure can be described easily, I would be pleased to learn. Secondly, if there is a minimum reading that should be found, I would appreciate that as well.

[ke6dcj]

Only if your multi-meter can read 100+ amps.

I suggest just going to a McParts store like PepBoys or Autozone, and having them hook-up an INDUCTIVE amp-meter to test how much current your alternator can put out at idle and at 3000 RPM with all accessories on (headlights, A/C, blower high; stereo).

It's free if you tell them you suspect a bad alternator (just don't buy one from them).

FWIW, the stock 500E alternator is rated at 110 amps. If you don't need the extra juice, most likely just have the voltage regulator/brush (VRB) pack changed.

Otherwise get a used 140-150 amp alternator from a 1997+ E or S class; swap pulleys; install a new VRB pack; and a LARGE 2 or 4-gauge welder's wire madeup to hookup to the B+ of the alternator and distribution block (behind the LH electronics box). Check out the archive at http://www.500ecstasy.com on this upgrade.

:-) neil

[charnett]

Thank you very much. This is extremely helpful.

[ashyers]

A quick check may be performed with a multimeter by measuring battery voltage with all accessories on and the car running at various RPM levels. A charged battery will read 12.6v. If your alternator is not able to meet or exceed this level of voltage while the car is running with the accessories on the battery will be discharging. Hopefully your alternator will maintain 13+v!

Andy