Losing electrical power, but car still starts and runs

I’m driving a 1995 Mazda Protege with about 200,000 miles. It has been generally pretty reliable, and I have fixed things as necessary, but a DNR has been in place for awhile. The water pump is leaking coolant and replacing it is a $700+ job according to three different shops because of the labor involved, so I’m driving it (and keeping the coolant topped off) while I arrange to get something else. The temp gauge stays in the normal range. Yesterday on the road the car began to lose electrical power: the radio turned off, the gauge cluster and then the headlights got dimmer, etc. But it continued to run ok. When I got where I was going, I parked it for a few hours, then on the return trip the car started fine, the headlights and gauges were bright, but over the course of about half-an-hour they began to dim again. The car continued to run ok until I got where I was going and parked it. I’m not sure I want to drive it again until I figure out what’s going on. The battery is about six months old, and the alternator was replaced about two years ago. The serpentine belt is in place and seems to be in good condition. Battery connections and cables look ok. The “charging” warning light has never come on. The water pump has been leaking for a couple weeks, but this is the first time the electrics have acted weird. Would the alternator go bad this soon? Does the water pump affect the electrics? What do I look for?

My own guess is that the alternator is on its way out again. This can be tested - even quickly & cheaply with a voltmeter. You also have to worry about the main power cables for the alt / battery. If they are old & corroded & producing too much resistance they could be heating up over time making for even more resistance. The next time everything started to go screwy I would be putting a meter on the alternator connections.

However, its also possible for the leaking coolant to be contaminating the belt & causing slip. It would be plausible for this to happen without a lot of noise or burning/heat b/c the coolant is acting like lube.

If you call around you can probably get a better quote on the water pump - which should have been done with the last timing belt. (If you’re saying “timing belt? What’s a timing belt?” Then its a miracle the thing is still running at all).

Check for a bad connection in the main power buss wiring under the hood along with a bad fusible link connection.