Bill,
I did not see anywhere where you stated the model.
I had that fault develop on a '99 V70 T5 about a month after I bought
it. The vehicle was under a years warranty so I took it back three
times and they never found the fault. They changed the bulbs, checked
the connectors, which were all like brand new, checked the earth runs
and changed the sensor pack.
The sensor pack is a switch relay with reed type connectors which
should switch simultaneously and only fail to do so if there is a
variation of amperage drawn through either coil due to a fault or
mis-matched bulbs.
The usual cause is a bulb on the way out and it's resistance has gone
up\down realtive to the other and the cure is to change both. Mine was
due to none of the standard reasons I have seen on any Volvo boards
and I just resigned myself to living with a momentary flash of the
bulb out lamp which had no pattern, other than foot brake operation. I
had a career in electronics and would have loved to have nailed the
problem with a multi-channel memory scope but other factors in my life
were more important<g>.
The fault, which I always suspected was a floating voltage (lack of
lock down on stability of the power rails) ended after a battery
change 6 months after I bought the car. Some batteries die very
slowly, as did mine, but many just fail out of the blue. I feel sure
that many of the Volvo electrical gremlins are due to battery related
issues and saw in the last month of mine, onboard computer zeroing,
clock going to 00.00 and three Electronic Throttle alarms. I put the
biggest, best 4 year warranty battery on and have never seen a problem
since.
Liam
