warning light

Guest · Post by **Guest** » 28 Dec 2004, 15:03

there is a warning light on my 740 that only comes on when i press on the brakes. it looks like a light bulb with and exclamation point in the middle and lines coming out from it. this light only comes on when i press on the breaks and the lights are off. it doesn't come on when the lights are on. what does this light mean and what could the problem be?

LaRy · Post by **LaRy** » 28 Dec 2004, 15:59

Probably is one of your braking light bulbs broken. Start looking at that!

Guest · Post by **Guest** » 28 Dec 2004, 16:22

i forgot to mention, the brake lights all work. that's why i'm so confused.

Kmaniac in California USA · Post by **Kmaniac in California USA** » 28 Dec 2004, 19:46

My 1986 740 GLE suffers from the recurring "No Bulb" light. Here are some tips to try:

1. The brake light bulbs have dual filiments, one for tail light and one for brake light. These bulbs can sometimes degenerate, causing voltage leaks between circuits. If your bulbs have been in for some time, I would suggest replacing both for good measure.

2. The bulb holders have metal tabs that make contact with the printed circuit metal on the taillight assembly. Over time, these contacts become deformed and corroded. If the problem persists after replacing the bulbs, then do the following; Polish the tabs with steel wool to remove any corrosion; bend the tabs slightly away from the bulb holder to allow greater contact force; lube the tab surfaces with silicone (dielectric) grease.

3. Be sure the check your electrical connections in the trunk, including the ground wire for integrity. Lubing them with silicone grease won't hurt, either.

This was a continuous problem with my 740 when I bought the car. I think it was one of the many little problems that convinced the previous owner to sell the car to me for cheap. Once I did the above, the problem went away. From time to time, however, the bulb will come on again. I have narrowed this one bulb holder than looses connection with vibration over time. I just wiggle that holder around in the socket and problem goes away for awhile.

TAFinley · Post by **TAFinley** » 29 Dec 2004, 07:14

Great answer, Kmaniac. My '85 245 GL develops the same problem off and on.

The circuit that illuminates the bulb warning light relies on resistance through the bulb circuits. So, if you have a little corrosion on the contacts of one of the bulbs or the bulb is near the end of it's life, the resistance will change and the bulb warning light will come on even though the bulb is lit.

Clean corrosion from the contacts, use dielectric grease, and always replace bulbs in pairs.

In other words, follow Kmanaics advice and the problem should be resolved.

Guest · Post by **Guest** » 29 Dec 2004, 08:31

thanks abunch everyone. i opened up the light and i found out that the wireing harness was loose. so all i had to do was tighten it up.
thanks!
michael