Hi all,
Yesterday I was driving my car home. At home point the traction control kicked in for a brief moment and immediately after I noticed the battery light in the dashboard. I stopped to see what was going on. At first I thought a connector must've popped off during the harsh acceleration. This wasn't the case. I hooked up a multimeter to the battery and it was reading 11.6V. So the alternator isn't charging. Now the weird thing is that above 4k rpm the battery light goes off, but the voltage stays at 11.6V. I ordered the new part, but now (the day after) it suddenly fixed itself. Battery light is off, even at idle, and the battery is happily charging at 13.6V. Is this a sign of a failing alternator, or does the problem lay elsewhere?

The car is a 1998 Volvo V70 with the 2.5T (B5254T) with 560.000km.

Kind regards,
Jonathan

 

Check the positive battery cable terminal end. Where it is crimped onto the red cable - a poor connection develops. If there is a poor connection that terminal will get hot (very hot sometimes) after running for a while. That high resistance connection can cause charging and starting problems - that cable goes first to the starter then to the alternator.

Solution is a new positive cable, have replaced many.

 

I don’t remember the terminal being hot when i connected the multimeter to it. The car was also running for 20-25 minutes max. Ill try to drive a bit tomorrow and see if the problem returns.

 

You can also do a voltage drop test. Connect one lead to the output of the alternator (big red wire) and touch the positive battery post. Yes, positive to positive - in theory the voltage should be zero because the big red wire is doing all the work and should have less resistance than your multimeter. The circuit needs to be under a load (engine running) to be a valid test. Anything above zero is the voltage drop, and above ~.4 volts is bad.