Thread: Did worn alternator cause rough running?

I have a TD5 D2a that used to suffer from an occasional slight roughness over 2,500 rpm. It was reluctant to run over 3,500, and often ran a little rougher at higher revs. I suspected the wastegate modulator, which the previous owner had already replaced.
Recently the alternator failed (on a night trip, of course - but not too far from home). This was accompanied by an alarming array of warning lights, including the famous Amigos, which were all set off by low voltage.
Once extracted, the alternator showed a lot of fibrous gunk in the slipring chamber, worn brushes, and a badly worn slipring.
I sourced a new alternator (from TR Spares in Sydney - excellent prices and lightning-fast service) and fitted it. I believe I have a very good chance of obtaining and fitting new sliprings to the old alternator - I'll post the result if it works.
The car ran great with the new alternator. Today (4 days later) I noticed that it seemed smoother, so I ran it to 3,000 and it was still smooth. Then I stuck my foot into it in 2nd gear and it ran quickly and smoothly to a bit over 4,000. (4,750 seems to be the recommended max. for a TD5.)



Is it possible that the brushes were arcing at higher revs and causing interference that affected the engine management system? Perhaps there are other people who have been struggling with a similar problem to no avail.


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A bad alternator can cause all kind of trouble but mainly due to the output, it can have failures of charging then the systems will work only on battery power which will fail below 12V then then some sensors and ECM outputs will be lower or if it's some problem with the voltage regulator there are cases when the alternator's output is too high which can create overboost...also there are cases when one or more junctions are shot in the diode pack then there will be an AC component in the supply which can disturb ECUs

in a nutshell yes... a bad alternator can cause running issues...i've seen enough