My 2000 HX started doing the thing where all the lights and the engine power would pulsate with the SRS light blinking on when it gets really bad. I detected the voltage would surge up to 14.5v and even above 15v with these pulses so I determined the problem was probably in the alternator after I had cleaned all the grounds.

I ended up taking the alternator out but just putting the same one back in because I didn't really know what I was doing and ran out of time before a snow storm was about to hit. After this operation the serpentine began occasionally squealing, exactly as it used to do before a mechanic fixed it. I don't what he did, but he said he didn't replace it so I guess he probably just tightened it. The pulsing thing still happens, but it seems to be less often and less severe. Now here's the interesting thing: The squealing and the pulsing thing NEVER happen at the same time! I've gotten in the habit of keeping an eye on the dash lights and whenever the belt is making noise the light is steady and whenever the lights are pulsing there's never a squeal. Last night I actually saw the lights start pulsing the very nanosecond the squealing stopped. So I'm 99% sure this phenomenon is happening and there must be a relation between these two symptoms.

Any ideas what this could be? I plan on getting back under there to actually put the new alternator I bought in when enough snow melts and it warms up a bit, and also a new serpentine belt. I just wonder what could explain this. My only idea is that when the belt is squealing it means there isn't a full "grip" on the alternator and so it can't generate enough voltage to cause the surging. Come to think of it, I'll set the multimeter back up in the cabin and see if voltage drops to around 12v during the squealing.

 

Squeal can also be bearing/bushing related in the alternator.