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.

BTW, read 700/900 FAQ and make sure you put the white bulb sockets on the right side!

Do like Steve Ringlee says, then check car owner's manuals for OEM (European) type of light bulbs for your cars. If you do not have those light bulbs, buy them at Pep Boys. Check their "computer" next to the light bulbs for light bulb numbers for your car. These come in Sylvania packages (Osram, Made in Italy).

First check the grounds for the taillights and headlights: in the back body panels next to the light panels, and right behind the headlights. Clean and protect with OxGard electrical grease (Home Depot/Lowe's)

Then check the sockets. Spray with Caig Labs DeOxIt or brush VERY LIGHTLY with a brass brush. Clean and protect each bulb base with dielectric silicone grease (auto store). Use identical bulbs on each pair, from the same manufacturer.

On my 740 the metal "tab" that grounded the bulb broke loose of the circuit, causing an open. I did some work with a solder iron and fixed the issue, double check, I know a combination of heat and some subwoofer action took their toll finally on mine,
steve