High Beam gremlin - PeachParts Mercedes-Benz Forum

300TDT 1987 · #1 03-15-2012, 04:28 PM

1987 300TDT with Euro lights.

High beams will work very sporadically, about 5% of the time.

Checked the combination switch have continuity for both flash and high beam. Replaced fuses and bulbs.

Checked the high beam fuse, had 12+Volts when I switched the high beams on.

I'm assuming because of this that the exterior lamp monitoring relay is fine, please let me know if this is not true.

So where too next? I think the ground would be the problem but the low beams work 100% of the time as do the fog lights.

Any suggestions are appreciated.

daw_two · #2 03-15-2012, 05:06 PM

Okay, I have almost the exact opposite problem. My high beams work too much. When I place the combination switch in the dim position, the high beams may still be on. If I barely pull the stalk toward me, then the high beams will go off; leaving the low beams on. 30 seconds later (maybe 3 minutes later), depending, I look down and the high beams are on. This is much more visible at night.

Is it the combination switch or relay?

300TDT 1987 · #3 03-15-2012, 05:19 PM

Quote:

Originally Posted by daw_two

Okay, I have almost the exact opposite problem. My high beams work too much. When I place the combination switch in the dim position, the high beams may still be on. If I barely pull the stalk toward me, then the high beams will go off; leaving the low beams on. 30 seconds later (maybe 3 minutes later), depending, I look down and the high beams are on. This is much more visible at night.

Is it the combination switch or relay?

Daw_Two I think you need to check continuity in the combination switch first. You'll need a multi meter and pull off the lower panel but it's pretty easy.

Check out post #8 on this thread as to what pins to check. Dead High Beams

Check them when the combination switch is in high and when it is not. If you get continuity when it is not in high beam position then it's the combination switch.

shadetree77 · #4 03-15-2012, 05:37 PM

i got a problem with my stalk too; if i push the windshield washer the low beams go out...

300TDT 1987 · #5 03-17-2012, 05:03 PM

Anyone have any idea's on my original post.

I just can't figure this out

Bio300TDTdriver · #6 03-17-2012, 05:31 PM

Once you get them on, do they stay on until you move the switch? When they are on do you have trouble getting them back to the low beams?

300TDT 1987 · #7 03-17-2012, 05:59 PM

Thanks for the reply.

They don't come on very often (I've stopped trying at night, no lights at all is scary).

When they do come on, I can put it back into low beam no problem. Then most likely they will not go back to high if I try them.

Bio300TDTdriver · #8 03-17-2012, 06:11 PM

Quote:

Originally Posted by 300TDT 1987

Thanks for the reply.

They don't come on very often (I've stopped trying at night, no lights at all is scary).

When they do come on, I can put it back into low beam no problem. Then most likely they will not go back to high if I try them.

Have you tried cleaning the contacts on the switch? That is where I would start.

300TDT 1987 · #9 03-17-2012, 06:32 PM

I cleaned the contacts for the combination switch, but are you referring to the light switch. I pulled it apart but didn't clean it.

If I'm getting 12 volts across fuses 14 and 15 in high beam does that mean the light switch and combination switch are working? That was my assumption and I've been to make some poor assumptions

Bio300TDTdriver · #10 03-17-2012, 07:05 PM

No I meant the combination switch. It just sounds like a switching issue. I think that because the low beams always work so it isn't a power issue or a fuse or ground issue.

Did you try new fuses even though you are getting power on each side of them? I don't think getting power across the fuse rules out anything without looking at the schematic. The power could go from the fuse to the switch.

I'm stumped.

jbach36 · #11 03-18-2012, 02:15 AM

Replace ALL of your fuses, with the copper types. I heard if you have the old ones which get pitted, they build up electrical resistance, and cause problems in other areas.

So, I doubt that's the problem with your lights, but for maybe $12, you can replace all of your fuses, and know for sure. This also might prevent other weird problems later.

Of course, it could be your bulbs.

300TDT 1987 · #12 03-18-2012, 01:48 PM

I've replaced all fuse's (with the cheapo's for the moment) and headlight bulbs.

If I activate the fog lights and put high beam on I still get the fogs on but not the high beam.

So I think I'm reading the diagram correctly, the flow goes combination switch, light switch, N7 exterior lamp monitoring system, fuse box, head lights.

Can anyone confirm this?