How long do voltage regulators tend to last?
 

Was wondering how long the voltage regulators on our cars tend to last....and whether at a certain point it makes sense to replace them "just because." On my 99, the PO replaced the alternator at 120k miles....now has 163k so I'm fine on that car. But on my 98, I'm pretty sure it's original alternator and VR at 90k miles.

So, those of you have have found a voltage regulator beginning to fail, around what mileage was that?

Thanks.

The voltage regulator last forever if not abused (i.e. shorted, reverse polarity), however, the brushes that is soldered to the regulator wears with use. Worn brushes can be replaced and the regulator should be good as new.

My alt lasted somewhere between 290-300k miles. Clutch went out.

Regulators
 

Brushes should last at least 100,000 miles providing you are not in an extremely dusty environment. As was previously written, brushes can be replaced if you have the right size replacements and the appropriate skill set. If not, a replacement regulator with new brushes is not expensive, as we know.

For a newly-purchased older used car with no known service history, I recommend replacing the regulator with a new one as part of "getting to know you" service. Put the old regulator in the new box and stash it in the car somewhere for an emergency. This little project gets you a number of things:

1. You learn to access the alternator and change the regulator at home and on your own time/schedule rather than on the side of the road in the rain with no tools while on the way to a job interview.
2. It gives you the opportunity to see the slip rings and gauge how far they're worn. This information will be useful when you find alternators on sale--should you buy a new one?
3. It gives you the opportunity to see if the alternator is the size listed in the owner's manual. Is it the original? Has it been upgraded by a PO?
4. The alternator now has a brand-new regulator, which should last many years. (If by some chance the new regulator is DOA, you have the old one to put back in and all your tools are already out.)
5. You now have a spare known good (used) regulator stashed in the car and you know how to do the job.

I should add that Mercedes seems to have given many of their diesels rather small alternators at the factory. Upgrading to a larger size is almost always a good thing--but that's a different thread!

Jeremy

There are a LOT of "getting to know you" service in an old car. So I would take the advice with a pinch of salt. Voltage regulators are solid state device so the chance of it going bad is very small. A lot of the times the problem is the carbon brushes or fray wiring. Worn out carbon brushes will give you warning, like a dimly lit 'Battery light'. Diesel will also run with or without alternator/battery so I would not do any Preventive Maintenance on the alternator unless you are scratching your bottom all day. Just run the sucker until it quits. And/Or carry a jump battery or AAA card.

This is my experience, others may differ.

Agree on not replacing the voltage regulator for no reason. I would recommend R&R to inspect the brushes. If they are too short (FSM has specs), then replace the VR or if you have the skills, replace just the brushes. Brushes are less than $5, where a Bosch regulator is $40 to $60 depending on where.