Bad Alternator Replaced. Curious if used alternator is good

[jimmy57]

The determining factors of regulator-brush unit vs. whole alternator would be bearing condition and rectifier (diodes) condition.
Bearings usually are not a problem but remove belt and spin alternator and listen for rumbling noise. Brushes will make some noise but that is a scraping noise.

Diode test is easy. Run engine at elevated speed of 1000-1200 rpm and turn on everything. AC voltage measured at output post should not exceed 150 mV. There will always be some AC voltage as the sine wave peak between phases yields some inconsequential AC voltage but a failed diode takes out a phase and makes the peak waves prominent and that increases the measured AC voltage.

On later models with clutched pulleys the clutch needs to be tested. Remove belt and turn pulley back and forth. The rotor should turn and then break free when you twist the other way. The rotation felt on the free portion should feel smooth.

[erikv11]

Is the diode part of the voltage regulator, so that a new VR replaces the diode?

[draser]

Alternator has a 6 diode bridge rectifier that suplies a continuous or dc voltage to the regulator. Any diode short will lower the actual dc volts and generate the whisling sound when load is turned on, such as headlights. Normal output voltage across battery with engine running is 14.4 volts. Anything lower means either leaky diodes, bad regulator or bad connections at batt posts, cables, etc.

[cn90]

In my experience, the VR goes out first (either very high or very low voltage).

The diodes rarely go bad (erik, the diode is separate from the VR in the Bosch units). In fact, when one buys a rebuilt alternator from places like Autozone, you may or may not get new VR or even new bearings.

[Herb Goltz]

I recently replaced the voltage regulator/brush assembly in my 2000 V70-- should be the same as the OP's system. My car had approximately 150K mi on it and the brushes were very worn. I would also measure for voltage drops on the positive and negative battery cables, as well as the B+ cable as mentioned by others. Have a look at my post for a place to buy alternator parts (no affiliation), the part numbers, etc.

https://www.matthewsvolvosite.com/forums/viewtopic.php?f=1&t=62367

[tonie]

I have a 1998 S70, not the turbo. Long story short, someone else took my alternator, power steering pump, etc. out of my car. They did not keep up with what went were and could not put it back together. I am now trying to put my car back together and have tried every bolt that has come out and none of them fit back in the two places that run through the center of the power steering pump and through silver bracket that goes in the back. I am aware of the size difference of the bolts but being that they were just tossed around I've had to try them all. I'm hoping someone can help me with the bolt placemen.

Thank you

[cn90]

@tonie,

Your best bet is a junk yard. Find similar year/model and take photos.
Then remove the bolts, PS Pump, Alternator, i.er., whatever you need and make careful note which bolt goes where.

[erikv11]

tonie, Here are some pics that should explain it. Let me know if you have questions.

In these pics the PS pump was previously removed, by taking out the 5 small bolts that screw into it. To put yours back in, first get the brackets and the alternator installed and set up to look like this, then you should only have 5 small bolts left, all the same size. Those 5 bolts mount the PS pump.

1 - Looking from the side where the serp belt is located. The long PS pump bolt/sleeve is installed across the top of the bracket but you will take it out at the end to install the PS pump. Note the 3 shiny hoes in the center, these will accept short bolts from this side to mount the PS pump at the end.

2 - Looking from the back of the alternator, not the medium size circle hole in the middle of the pic, the other two PS pump mounting holes are there. One hole at 9 o'clock has the black bracket overlaying the silver triangle bracket, the other hole at 12 o'clock is in the trainglur bracket only. The other two small PS pump mounting bolts will come in from the back through these two holes, and screw into the PS pump.

Alternator from the back, all mounted up, by 3 bolts. The longest bolt is at 4:30 or 5 o'clock, you can see the head because it comes in from the back side of the alt. Then the next longest bolt is the one at 2 o'clock, coming in from the serp belt side so you can only see the 13 mm nut here (the 12 mm head is recessed in the hole visible in the first photo). Then the final alternator bolt is at 11 o'clock, again you can see a 13 mm nut because the 12 mm head is over on the serp belt side pump side (visible in first photo).

To install the PS pump you now remove the long bolt with sleeve, re-install it through the PS pump, then put in the 5 short bolts. The 3 bolts from the front you have to get a socket through the holes in the PS pulley, one at a time. The 2 bolts in the back are easier, make sure you also attach the ECT sensor clip to the bolt at 9 o'clock.

Firs put in all of them semi-loose, then tighten them up when you get the pump in place and get all bolts lined up.

MOD REQUEST: please rotate all photos 90 degrees clockwise, they are supposed to be portrait not landscape orientation, somehow the upload rotated them.

[tonie]

@erikv11 thank you for your help!! It looks like I'm almost done if I can get these last two bolts figured out.

[erikv11]

@erikv11 thank you for your help!! It looks like I'm almost done if I can get these last two bolts figured out.

I know my other post is long but luckily the pictures contain direct answers to your questions!

First, about the pic where you say "This is the back. right now I have just enough in to hold it in place while I figure out which bolts to use on this part." In your pic I can see the alternator bolt that I talk about in my picture 3, I call it the 2 o'clock bolt, you should look at it. It looks like you used the wrong one you need a slightly longer bolt so that you can put a nut on it. You will also need the nut. Your pic also shows two empty holes in the back of the PS pump, I talk about those in my picture number 2, I call them 9 o'clock and 12 o'clock. Read that pic caption, those holes accept short bolts that screw into the PS pump, bolts that are like like your top picture where you say "and I have this size. Yes I have extra bolts (again long story)"

There are no long bolts through the PS pump from the front to the bracket in the back. The PS pump only accepts short bolts, three from the front and two from the back, my post talks about those five short bolts. So, where you say "Now I'm stuck on this. This is the front, do you know which bolt runs through here to the bracket in the back? There are two of these holes I know they run through to the aligned holes in the bracket" is incorrect. You are referring to two of the three holes I talk about and show in my pic number 1, these holes accept short bolts that go through the front bracket only and screw into the threads on the PS pump.

Good luck, it is a puzzler but you will get it!