How do you determine if it's the alternator or the regulator that needs to
be replaced? I can not afford to spend $100+ for a new alternator, only to
find out that it was the regulator that was actually bad. (I have a good
quality multimeter that I can make measurements with)
At low and high engine speeds, the DC voltage remains at 12.4 V. The
battery is nearly new, and I'm confident that it is good.
Correct me if I'm wrong, but in my limited experience, when the engine is
revved at high speeds, the voltmeter should be in the 14+ Volts category,
not 12.4V!!! That way there is a re-charge on the battery. At least that
is what I've witnessed my ex-E 190 doing...
Really, if you own a '89 MB and cant spend a poor $100 then you probably
didnt choos the right car...
For the alternator, do you know any electronics? If you do and know how to
use that mulitmeter of yours then you should measure the diodes on that
regulator and check that they are ok. If they are, try to rev the engine @ >
1500, then the output should be above 13.5V. If the output varies a lot then
the regulator is probably broke...
Hey, change the regulator, if that doesnt fix it, do the alternator.
$100, whats that...
If you have the time, take out the alternator and do a couple
of checks. First of all, inspect the brushes. These are often worn
down to nubs on older cars. Next, using your DVM, check the
diodes. There will be a set for the field winding, and one for the
armateur (sp?). Also check the continuity of the windings and
the condition of the commutator.
These things are really pretty simple, and problems tend to be obvious.
If the alternator looks OK, replave the regulator.
Problem Solved ! :) Turns out that the brushes on the the regulator are a
normal wear item. I found a non Bosch version of the regulator at a local
automotive electrical store for $20.50. It took about 30 seconds to remove
the old one from the back of the alternator. There are simply 2 phillips
screws holding it on. Then, about 30 seconds to install the new one. Here
are the diagnostic readings I had:
Battery terminal voltage with engine not running: 13.01 Volts.
Battery terminal voltage with engine running BEFORE replacing regulator:
Battery terminal voltage with engine running AFTER replacing regulator: 14.4
The brushes on the new regulator appeared MUCH LONGER than the brushes on
the old... apparently defective regulator.
My advice: If you suspect an alternator problem... remove the regulator and
replace it. That's most likely the problem!!!!
dooh...of course they were longer...your old ones have worn...we are talking
frinction here...moving parts...touching
ooh and...I am pretty sure..in a couple of months, you will need to find a
Bosch version...cause not only the regulator side wears..but also the
alternator side...and from what I have experienced...the older the
alternator...the more it needs original Bosch regulators...
I am having the exact same problem with my '92 190E 2.6. My question is
what is the fastest way to remove the alternator for service? There
is very little room to work, did you remove it from the top or under the
car? and how long did the job take? any special
tricks?....thanks...Rick ( both cars are similar engine layout )
I'm sorry the (very important word) NOT was dropped somehow. I did NOT have
to remove the alternator to change the regulator. I don't know the steps for
removing the alernator, but I'm sure there are a bunch here that do.
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