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Discussion Starter #1
I have an 89 420sel. I have a major electrical problem. I recently replaced the alternator because it was exhibiting symptoms of it going bad. I put the new one in and now all of the lights pulse rapidly. I replaced the battery as well and it still does it. The alternator charges the battery, but after it warms up a bit something causes the alternator to stop charging the battery. Any input would be very helpful. Thank you.
 

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Discussion Starter #3
Its a duralast. I think its a remanufactured one. I had it tested and it tested good. Could it be a component of the alternator?
 

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1983 300 SD, 1991 420 SEL, 1979 300SD
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536 Posts
probably the voltage regulator; if you still have the old one try swapping it out since it's quick. otherwise it might be a loose ground somewhere (maybe the strap)
 

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1983 380SL, 2000 S430, 1991 420SEL (retired) - RHD
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5,507 Posts
+1 on the regulator and ground check. Check the regulator code- wrong ones can still fit the alternator. The latest Bosch code is 1 197 311 028. My original was 1 197 311 009.
 
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