I was driving on the freeway tonight and passed someone who was going very slow. When i accelerated I heard a soft whoosh, then all the warning lights came on. I drove it home as the temp stayed normal...then checked under the hood when i got home, nothing abnormal. It broke down yesterday-I got a new battery. I've read that when all lights come on it has something to do with the charging system. Vehicle starts up easily still, though all lights remain on. Could it be a blown head gasket? I've been adding water daily for months now as the head is ("dented in" due to a loss of water when the radiator blew last year...this, according to my Volvo guy (he just retired so I can't ask him any follow-up questions). I appreciate any insights you guys might have--thank you!

 

All the warning light are showing on the dash (except for the oil pressure warning light I hope) because the alternator is not recharging the battery. That's how all the warning light bulbs are tested, they come on before the alternator starts charging. You "broke down" - I trust that means the Battery went dead, and you replaced it. Because the alternator is not charging the battery back up - as soon as you use the stored current in your new battery from driving or running the engine - the battery will be dead again.

The cars is not overheating - that tells me the alternator belts are still on and spinning the water pump. Good thing.
So if the alternator belts are tight (do you still have 2 alternator belts?) Simply check the voltage at the battery with your $6 voltmeter. (harbor freight)

A fully charged battery is ~12.5 volts. When the car is started a working alternator should raise the voltage at the battery to 13.2-14.5 volts. There are three wires going to the alternator. The small red wire goes to the warning lamp bulb in the dash. The light is working meaning the wire is ok or at least grounding out somewhere. Disconnect the small red wire from the alternator and see if the alternator warning lamp is on or off with the key on. If the light is off - that open circuit happened when you unplugged it - meaning the wiring is ok. If that warning light goes off it means the ground wire to the alternator is ok also. It's attached to the bottom of the alternator and needed because the alternator is mounted in rubber. The 3rd wire is the big red wire bolted to the back of the alternator - that goes directly to the battery (via the starter) If the warning light stays on when the small red wire is unplugged it is grounded out somewhere, most commonly in the engine wiring harness where it is shredded near the back of the valve cover at/on the firewall. Don't touch those wires if the insulation is coming off of them - you will only make things worse. If the wire is grounded in the harness you will have to run a new wire from the firewall to the alternator. (or replace the $$$$ harness)

Belts are good, wiring is good, voltage is ~12.5 volts or less at the battery when car is running - means you have a bad alternator.