Hi Andrew,

Now you're on the right track. The test light is unlikely to find
your trouble. The so called "Noid light" for checking injectors is a
great idea since the pos and neg legs are both switched people can
get fooled measuring to ground when they need to confirm both pos and neg
legs are active.

I found some nice little multimeters on sale recently via the craftsman tool club. They were about $12-15 or so and just fine for troubleshooting
your car. I bought an extra one for my glove box.
Rat Shack has meters for $25 or so that will be OK
The booklets will explain the basics and soon you will be better able to
troubleshoot electrical problems. You should get the Volvo Green book wiring diagram for your model year car. It is perfect for troubleshooting.

In series means you remove the neg cable from your battery
and set the meter on DC amps.... (start with the highest range in case there
is some high current flowing, and you have everything off) then connect one probe to the battery cable end you took off and the other probe to the battery
where the cable used to be. Thats in series which is the way to measure current.

You can measure DC volts easier by just placing the probes on either battery terminal You should see 12.6 VDC with the car off and about 14 vdc with the
car running and the alternator working.

Post back with results

Bill