9 replies to this topic

[mbsl98]

I have diagnosed the source of my burned out heaadlights as an overcharging alternator. With car running, the current at battery and at light plugs is a little over 17 volts, with result that all four headlight bulbs have blown (Silverstars)at nearly the same time. I expect that something was damaged just before this occurred as part of a fuel pump failure that resulted in a tow, dead batery and resulting jump and recharge from a local shop. The fuel pump issue was a bad wire connection inside the fuel pump canister, not actually the pump but that is just an aside. My questions now relate to replacement of the whole alternator, or just replacement of the voltage regulator. I don't pretend to know much of the workings of the alternator, but since it is capable of putting out 17 volts, my guess is that the issue is just in the regulator itself. If so, I know I have replaced regulators in 740's in just a few minutes. However, I have never seen much about replacing them on 850's, and FCP does not show a separate regulator. Eeuroparts does show the regulator as a separate part (about $80.) and lists all 850's as compatible. Then Autohaus shows two very different regulators for the 850, with no comment on which fits which.

Any thoughts about the prospects for a regulator swap, and its probability of fixing the problem? Also, if it is a separate part, can it be done with alternator in place, or needs to have alternator pulled? Haynes suggests that pulling the alternator is a pretty easy job - correct? I have done a search and found a couple of threads but no consitent answers - some said regulator can be swapped, some said no, and not much on the actual process. Thanks to all,

[Gilhuly]

When you pull the alternator take pix. You have to keep track of some brackets etc. It'll help.

[AlvinL]

Where did you get the replacement voltage regulator?

EDIT: Nevermind, I reread your post. It should work and hope you don't have any problems taking the alternator apart.

[bottlecap]

i believe the regulator is inside the alternator housing. it is usually recommended to just swap the alternator as it is a lot faster. since you are doing this yourself, maybe it's worth a shot to try swapping the regulator.

at any rate i'd get a voltmeter and measure the voltage across the battery with the car running to make sure it is the regulator before you start taking things apart. voltage with a failed regulator should be way > 14 volts (mine was 18 when it went). it is also possible it could be very low but i don't believe they tend to fail that way.

-mike

[mbsl98]

I do have 17+ volts at both battery and at headlight plugs with engine running. Received the new regulator and will take things apart later today or tomorrow AM. I will be crossing my fingers that I got the right regulator - it is the round cap one that Eeuroparts shows as fitting all 850's. However, other sites list two regulators for the 850, one a rectangular cover and one round cover, so they are probably not interchangeable, and no info on how to determine what I need until I get it all apart. Haynes makes the alternator sound simple, just 4 bolts. Other posts here and on Matthew's suggest it is about an hour of removing other parts before you get those four bolts out. Then the regulator sits behind a black plastic cap that covers most of the side of alternator and is held in with tree small screws. Once that cap is off, the regulator should be simple to swap (if I have the right one).

[mbsl98]

The definitive answer: yes you can replace just the voltage regulator on an 850 with a Bosh alternator. It takes the round cover Bosh regulator ($79 delivered from Eeuroparts) and you can do it without completely removing the alternator. I pulled the power steering pump and upper radiator hose to get enough access to remove the black plastic cover on the back of alternator (3 small screws hold it on, plus snap clips). Then it is just 2 screws to pull regulator, and drop in the new one. I also pulled out the black box aaround the engine computer to haave more room to work on PS bolts - it is just clipped in. Now I'm getting 14.4 volts at the battery, slightly better than the 14.0 I was getting before the regulator blew.

[AlvinL]

I have to say that this is also a good fix for charging problems due to worn brushes. The new regulator comes with commutator brushes. It will at least breath a little more life to the altenator until the commutator itself or the bearings wear out, which does take a while .

[willst5]

Can anyone confirm that the 98 S70 power steering pump, serpentine belt tensioner, and pulley bracket are attached by just two bolts (one to the engine block and another to the alternator)? I'm hoping to replace just the regulator, but might need to pull the whole alternator. Thanks.