okay here's a fun one for tech.

i have a 1990 240 that i am preparing for the dreaded md inspection and here's my problem.

i have cleaned out both rear light casings -- put new bulbs in -- and the brake lights work when the main lights are NOT on. but.... when all lights are on, the brake lights continue to be engaged in the "high" mode -- even though the rear window brake light is off and the brakes are not being applied. -- therefore, at night, it looks like i am driving with the brakes on.

in the day, there are no lights on -- but when you apply brakes -- the brake light comes on -- along with the rear window and all is well.

now, i have also checked the connectors on the sockets, made sure i am using the correct 1157 bulbs and i have switched the barrel under the driver's side panel -- so none of those things seem to be a problem. i have even checked that switch under the brake pedel where you push the brake pedel and the it makes the lights come on to begin with. -- there doesn't seem to be a problem there.

there is no water build up in the lens (i have drilled a very small hole at the bottom, using a 45 degree angle so in case water does get in (as you know sometimes happens with 240s) it can drain and dry out quickly.

i even took lens off and cleaned at all the schmultz -- like leaves, mud etc. -- as i said, i am getting the car ready for inspection -- i am purchasing it from a woman who didn't take optimum care -- but hey, it's a volvo and this will be my 4th 240.

any suggestions as to whatelse i can do short of taking to a dealership and buying new circuit boards for the two light boxes in the rear.

Also, another thing. how do you get the (1) fog lights on. i had them on through happenstance but have no idea how they came on or how i turned them off. i am preplexed about this, too.

thanks much.
volvo girl. :)

In a word "earth"

the little ampies need to get OUT as well as IN so if they cant get out they try a short cut - hence other lights come on

good luck :57:

i don't know what you mean by this. how do i get the little ampies out?

all metal parts of the car are at Earth potential because the earth on battery is connected to the chassis/engine

so generall a wiring harness eg to taillights only has the 12V positive wire and the other side of the bulb etc will be either earther by dint of being in contact with car or will have a short lead to nearest point to earth

if you just removed assembly to clean AND wrong lights now on THEN all points to bad/no earth

so just check out the earth wire

and ampies/volties/watties are the little electron guys running down yr cables, through the light and diving into the big earth puddle [thus bringing the entropy to zero]

BY earth he means the ground wire that goes onto one of the studs for the taillights.

Also make sure the circuit boards aren't burned or the plug.

so did it solve the problem?

always nice to get feedback

i ended up taking my new baby to the volvo dealership. will get her back next week. i have tried everything - but with no success! at least, when i changed out the windshield wiper motor with my dad -- it works! so i did have some degree of satisfaction as all women should know that there is more to car maintenance than driving to jiffy lube. but, to no avail, the backlight mystery will have to be solved by a trained professional. considering i bought the car for $1,000.00 and the volvo dealership said it was one of the best running 240s they've ever seen, i don't mind making the momentary sacrifice of self fix.

thanks guys. i will let you know when i need more troubleshooting. i am glad i found this forum.

:clap:

So are you saying you DID check the earth/ground and it was OK?

i checked the wire connnection and it was fine but i have a feeling it is something where the wire needs to possibly be replaced -- or the circuit board has got a bad spot in the brake socket plug. i noticed when we were cleaning the lights that one brake light circuit copper had been serverely sanded -- it was not smooth like all the others -- it was all roughed up. so i have a feeling it may be a combination of the two things. that's why i went to the volvo dealership.

You could have replaced the circuit board your self in about 10 to 15 minutes.
Alot of the times that is the problem with lighting problems on these cars.

I actually took the time to solder wires between the lamp holders and the circuit card in the tailights. It has worked fine for almost 2 years.

In case anyone dont realise - on your $5 multimeter there is a resistance setting [at 6 o'clock for 200 ohms] so you can quickly test from the neg side of the globe to the car body and should get < 1 ohm if all is well


errr - do this with light OFF