I was recently driving my 99 Volvo s70 home and the brake, abs, headlight malfunction, and traction lights all came on. I stopped at a light, or the shifter in park, and then tried to go again, and it barely crawled through the light and I had to get it towed. One alternator replacement later from a v70, and it's okay, until the headlight stopped working and my alternator seemingly overheating. The wire to the battery is very hot. Please help, I can't figure out what's causing my car to overheat. Even saw smoke from the alternator when I got it home

 

sounds like your replacement alternator's voltage regulator went bad and is overcharging. If you put a volt meter on the car it should be making about 14- 14.5V at idle. you may find the alternator actually blew out both headlight bulbs (I had to replace both my bulbs after the alternator went on my 850). The only other thing I can think of is that the bearing may be bad on the alternator as well - so you may want to consider getting a new / refurbished unit and correct both at once.

 

So do you suggest I find a new voltage regulator or a whole new unit? Something may have caused the original alternator to go bad and is starting to make this one go bad too, is there any way I can check something like that?

 

Good point. Thinking aloud, if there was a short it would either blow a fuse or kill the battery (ie if the short was say between the battery and the starter motor or something that could sink a lot of current). If you have a volt meter, start by measuring the battery with the key off. Should be 12.6V or so. If the car cranks, your battery's holding a charge which is a good thing. Start the car and now measure voltage. if its over 15, turn off the car as you'd suspect the voltage regulator and you don't want to overcharge the battery. If the voltage seems in range, the heated cables/terminals are probably due to a bad connection or corroded wiring within the cable (ie resistance => heat) so check the connection to the battery and alternator, look for any burnt or missing insulation. You may want to replace the battery cable(s) just the same and check the big cables like battery to starter, battery to ground as well as the wiring to/from the alternator making sure they have clean contacts and are fully tightened.

 

I checked all that and everything seemed fine except the voltage on the battery being far too high. I proceeded to get very frustrated and on a limb I went to get yet another alternator because I had a hunch it was the regulator, and it was. With the new alternator, she's running perfectly at 14.3v! Thanks a lot, I appreciate the help! It was bad luck on the replacement alternator off the junked v70 i guess