1999 S70 new alternator & battery, not charging

[VolVoguy10]

I just replaced my alternator for the 2nd time this year. the charging system was working fine until after I tried to get to the carbon canister. I did not get it off, so I put everything back together. Within a short time the car died because the battery was low. Charged it up and had the battery and charge system checked. The battery was good but system was not charging. Replaced the alternator (under warranty) and within 30 miles of driving the battery is low. I checked the connections at the battery, alternator and in the trunk where I had disconnected while trying to get the canister out. What am I not seeing?





















i

[shaker_chi]

Have you had the alternator tested? If it tests good, then get yourself a multimeter and start checking your system. I would start at the alternator itself then work yourself through the starter and on to the battery. It seems you have a bad connection between your alternator and battery. I have changed alternators on a 94 and 98, but never a 99. I'm not sure where the cannister is and why that should come into play.

[jreed]

I have no experience with the '99 but on my '97 the positive battery cable was bad at the positive terminal. It was a hidden defect that only showed up under load. To see if your cable has a problem, the best way to diagnose it is with the "Voltage Drop Test" using a multimeter to measure the voltage drop across each connection and segment of the cabling until you find a voltage drop that is larger than specification. That will help you pinpoint a cable problem if it exists before you get into replacing components.

[JRL]

You need to replace the B+ cable and probably the positive cable
This is a common issue on these cars.
If you don't, it will never charge.

Do a very simple charge system check, this will tell you which, if not both, cable is bad.
I'll bet if you touch either cable it will be VERY hot!
You probably wasted a ton of money installing a new alternator, it's probably just fine.
If the car has over 100K miles and those cables have not been replaced, replace them NOW

[VolVoguy10]

Thanks, I'll give that a shot. B+ is the one going to the alternator, Right?

[rspi]

I think it's the smaller wire going from the battery to the fuse box.

[BEJinFbk]

Don't spend any money replacing anything until you can verify the problem.

A simple meter and learning how to use it can save you hours of frustration
and bundles of cash. Charging systems tend to appear a lot more complex
than they really are. Once you've worked through a couple, it gets easier.

Breaking the system down into smaller segments is the best way to go.
Look at each component, cable and connection methodically and thoroughly.
Battery, Alternator, Regulator, positive AND grounding cables along with all
of their connectors.

Search "Voltage Drop". This will show you how to measure voltage at each end of
all of the cables in the system. It's kinda like looking at how many gallons go into
one end of the pipe versus how many gallons make it out of the other. As posted,
there can be hidden issues that a meter will see when your eyes won't. With old
cables, power can just disappear in rotten copper and corroded connections.
Checking for hot connections can also be helpful with finding "bad" spots.

Search "Alternator Test" and "Battery Load Testing" for more useful info.

And remember -When something like this happens right after you've been
wrenching on the car, it's almost always something that you touched!

Good Luck!

[abscate]

The evap canister is under the fender (early models) or the back of the car (later).

Are possibly trying to read the PCV box which is under the alternator, somewhat?

[Vlvspd]

Check all of your grounds!

[JRL]

Oh for God's sake, if the cables are original I'll bet the farm that's the problem.