Volvo Repair: Service Light on Dashboard, mile intervals, mileages

Question
QUESTION: Roger:
You were such a big help to me with my recent headlight wiper arm problem (all fixed now, thanks again) that I am now coming to you with another question, this time relating to the dashboard "Service" light on my '93 Volvo 850GLT.  I believe that the "Check Engine" light on newer vehicles comes on when an onboard computer detects an actual problem, but apparently my light is less sophisticated - according to my Owners Manual, it simply comes on (for a brief period) each time the engine is started after various mileages, driving times or calendar intervals are reached and will continue to do so until a service technician resets it (hopefully after performing some appropriate service).  The most recent service on my car was the 120,000 mile one (the most major level, to be performed at 30,000 mile intervals), but it was done a tiny bit early with 119,976 miles actually showing on the odometer.  Shortly after getting the car back from the shop I noticed the Service light coming on as described above and I'm guessing that the technician never reset my system so that it was triggered when I actually hit the 120,000 mile mark.  Does that sound like a reasonable explanation to you and, if so, can I do my own resetting without special tools or knowledge or must I make another visit to the shop?  Of course, I suppose I could just continue to ignore the light, but it sometimes makes my passengers nervous!
Ed


ANSWER: Ed, you can do this.  Follow these steps.  Go to the 2 little blocks by the washer resevoir.  REmove the left cover and put the pin in position 7.  Turn key to pos 2.  Push the little button 4 times, wait for the light to go off, then push button 1 time, wait till the light goes off, press button 5 times, wait for light to go off and finally hit the button 1 time.  The light should flash rapidly and now the light is reset.  Take care.  Roger

---------- FOLLOW-UP ----------

QUESTION: Roger:
Thanks for your usual quick response.  I was aware of the two blocks by the washer reservoir but the rest of your answer kinda stumped me - I had no idea what "pin" or "little button" you were referring to and I initially assumed that the "light" was the dashboard "Service" light itself!  However, now that I've actually gone under the hood and removed the left cover, things are pretty obvious: the "pin" is the metal-tipped wire lead that is right now parked in a sort of holding socket on the cover; the "button" is right there on the body of the block; and the "light" is that little reddish blob next to the button.  That being said, I need some clarification as to what you mean by pos.2 of the key.  As I see it, the key has four positions: (a) Off (key can be removed), (b) Power to Accessories (e.g. radio), (c) Operating (i.e. while driving) and (d) Start.  I'm sure your pos.2 corresponds to either my (b) or my (c), but which one?  Also, you never said whether you concur with my theory as to why the Service light is lighting up in the first place.  Sorry to be such a noodge but, as you've probably noticed, I am a super-cautious rank amateur.
Ed  

Answer
Ed, the light comes on after 5000 miles or whatever the factory set it at.  Whoever reset it last reset the counters to 0 and after 5000 miles it comes back on.  Yes pos 2 means all instrument lights on and car not running.  Its good to be cautious Ed but relax.  You arent going to break anything.  Roger