Hello people, I am having trouble with the low beams of my 1991 740.I changed the bulbs and the dimmer switch and they still dont work.My high beams work fine can anyone help me out.and I checked all the fuses they are fine also please someone help me out.Thanks

try checking the relay. as the switch cant handle the big power switching required for the lamps, the relay does all the hard work. one side of the relay could have died. its easy to test with a continuity meter or volt meter accross the terminals.

SykO

can you tell me were the relay is I dont have a book for my car I see a few relays under my radio is it there and if so witch one is it.

make sure the contacts on/around the bulbs and the wires going into the bulb holders aren't corroded or rusted. Use a multimeter to check how much/if you are getting power at the bulbs.

According to the electrical schematics, power for low beams comes from the high beam relay "K", to the high/low beam switch on the steering column, goes through the bulb-out sensor, then #'s 19 & 20 fuses, connector "A" at right A-post and then directly to the headlights.

Sounds like the only two things left to check not suggested yet are the bulb-out sensor and the connector at the A-post.

my brake light problem came down to corroded sockets along with a bad brake light switch.

I have had a similar problem with my lights. Problem follows:

I recently added an amp and subwoffer to my 1991 740. when we reconnected the battery the headlight switch was in the on position. Now when I move the headlight selector to the on position, the dash lights, parking lights, license plate bulbs and headlights are all off. When I move the selector switch to turn on all the running lights, the parking lights, dash lights, and rear tail lights all come on. the only way to have Headlights at night I have to pull and hold the High/Low selector to make the high beams come on. When I release the High/Low selector the high beams turn out.


Thanks for all your help and advice in advance.

P.S. - I replaced the "K" relay(no change) and I have Checked all the fuses.

From what it sounds like you have burnout out the contacts in the switch from where you left it on and reconnected the battery. there is quite a lot of current flowing with the headlights and by leaving them on and re-connecting the battery it could have knackered the switch terminals.

When you connected the battery, did it arc at all? like sparks etc?

Matt

Where is the bulb out sensor and the connector at the A post? Thanks

Matt, we have another headlight switch, is that the switch you think went bad?

Thanks, Tim

Soupbone, did you ever get yours fixed ? sent you a PM. Tim

Hey all, I have the exact same problem. I had reinstalled the radio and lost my lights too.
(I recently added an amp and subwoffer to my 1991 740. when we reconnected the battery the headlight switch was in the on position. Now when I move the headlight selector to the on position, the dash lights, parking lights, license plate bulbs and headlights are all off. When I move the selector switch to turn on all the running lights, the parking lights, dash lights, and rear tail lights all come on. the only way to have Headlights at night I have to pull and hold the High/Low selector to make the high beams come on. When I release the High/Low selector the high beams turn out. )
A guy stopped by and helped me briefly and said the relay may be toast which is located just in front of the fuses (the fuses checked out okay). However I dont know which relay and when I called the local parts store they dont carry it, they said its a dealer part. I tried reading this forum and am more confused as to a fix. Can anyone help? Thanks in advance.

the bulb out sensor (in mine) is a green cylindrical unit in the relay panel behind the fuses. the A pillar connector is either up and the steering wheel or a similar place on the passenger side.

mredi1 - yes have a go at replacing that, is the large rush of current drawn from your headlights when left on and re-connecting the battery could have burn out he switch contacts.

Matt

Thanks, Matt, we will have a look for that today. Yesterday we replaced fuses, headlight bulbs, headlight relay and headlight switch - no luck. Any idea how hard it is to change the dimmer / turn signal lever/switch ? It maybe this as well. Will look for the bulb out sensor. What is a pillat connector? We have a chilton manual but it does not cover some of this. We have been using the headlight schematic to eliminate parts. I do not see a pillar connection. Thanks for your help. Tim

NDM Farms - The headlight relay in mine is in the first row next to the fuses, 2nd from the left and has the letter K on it (at least in mine and the used one I got). Hope that helps, it was not that in ours, do we continue to eliminate things.

the dimming switch on the stalk, you have to remove the covering on the steering column to access it. it should be held in place by 4 screws i think, possibly torx heads.

Matt

Matt, we will check it out, I thought it might be more complex than that. Thanks Tim

the dimmer /turn signal is just a set of switches in one housing, some spdt some dpst etc... just how it is wired up. It switches between circuits in the relay.

Matt

mredi1-thanks ill check it out

Okay, I was able to finally find extra relays. I switched them out and still nothing. I was installing a new radio tonight and happend to find the wire that goes to the lights was cut. I believe the guy who owned it before me or who ever installed a different after market radio had tapped into this wire, maybe for the dimming feature. As soon as I plugged into it my headlights began working again. No more holding down the high beams!!