I understand that it must be a ground wire or circuit board problem, but I am a novice at this kind of thing and the 700/900 FAQ section doesn't seem to have any step-by-step instructions on how to remedy this frustrating problem.

Anyway, I have the bulb failure light on for both my 1990 740 GL wagon and my 1994 940 wagon. The headlights and front blinkers all work fine for each car. I have replaced the rear bulbs on both cars, however, even though the bulbs I removed looked perfect. Interestingly, I noticed that the right tail light bottom bulb was 1157 on both the 740 and 940, but the left tail light bottom bulb was a 2357 in each. I wonder why the difference? The other bulb sizes (reverse, brake) were 1156, as I recall. Does this sound right?

So after replacing all the bulbs, I still haven't gotten anywhere. The 940 has only one brake light come on when I depress the brake, and when I put the right blinker on, the parking light and reverse light alternate, which looks odd. When the headlights are on and I press the brake, the tail lights turn off (dangerous!) and only the center brake light luminates...so I can't safely drive this car at night. I have had these problems ever since I bought the car about 3 weeks ago.

On my 740, I've had the bulb warning light turn on every so often within the last year and a half that I've owned it, but I could never find which light was out. Well, lately when I have the headlights on only one tail light has decided to work, and even though both brake lights seem to work okay, when I depress the brake without the headlights on, the bulb warning light comes on. This is a newer problem, but since I replaced the bulbs I'm assuming this must be a ground wire issue as well.

I appreciate the prompt response to my last question about the overdrive relay being bad, so I hope I can also find some insights about my tail light problems. I can't drive these cars safely until this is taken care of, I'm afraid.