Headlight issue, low beams cut out when high beams are switched.

[clarkson]

Hi r3vlimited,

So I am almost finished my rhd conversion and have fitted some rhd headlights.

When I have the low beams on and flash the high beams or push stalk forward to activate them, the low beam lights drop out until I deactivate the high beams.

Has anyone encountered this problem? I have yet to do any real testing but maybe someone knows this issue and can point to the problem straight away.....(wishful thinking lol)

Car is 1987 built USA spec m3.

[shameson]

This is a common issue, just that the wiring is different since it wasn't meant to have those lights. On my last two e30s when I converted them from sealed beams to ellipsoids, it was like that. One option you can solve it with is by soldering a wire connection between two pins of the relays. I had a thread on it let me dig it up. It's not the best fix honestly and I only bothered to do it on my first car, but it did work

Edit: looked it up and if I remember correctly you solder a jumper between pin 30 and pin 87 (?) of the low and high beam relays

[blazinxpk]

this isnt a problem, its how the car is stock. if you want to change it to have both lows and highs and maybe even fogs on at the same time you will have to modify the appropriate relay(s).

[clarkson]

So this is factory USA spec design? Not an actual problem just the way it is configured? Interesting. I am going to compare the wiring digrams for the M3 as opposed to a later E30 that doesn't do this...

[clarkson]

Worked out the problem. This car originally had H4 low beams, which ran a high beam aswell as inner lights. So when you activated high beams, the inner lights lit up, the outer low beams drop out and the outer high beams fire up. So you have 4 high beam lights running. Wow would be friggin bright.

Anyways, the the high beam relay is a sneaky 5 pin relay and pin 87a feeds pin 30 on the low beam relay. When the high beam relay is energised, it transfers power from pin 87a to pin 87, leaving pin 87a high and dry. Which is why my low beams are dropping out.

So solution is to pull fuse box and get a fresh feed to pin 30 on the low beam relay, bypassing the feed from the high beam relay.

[maxmonster]

Doesnt pin 30 to pin 30 work too?

[DaveSmed]

Worked out the problem. This car originally had H4 low beams, which ran a high beam aswell as inner lights. So when you activated high beams, the inner lights lit up, the outer low beams drop out and the outer high beams fire up. So you have 4 high beam lights running. Wow would be friggin bright.

Anyways, the the high beam relay is a sneaky 5 pin relay and pin 87a feeds pin 30 on the low beam relay. When the high beam relay is energised, it transfers power from pin 87a to pin 87, leaving pin 87a high and dry. Which is why my low beams are dropping out.

So solution is to pull fuse box and get a fresh feed to pin 30 on the low beam relay, bypassing the feed from the high beam relay.

You nailed it dude. The 87a pin is fed from a small, usually yellow jumper wire. I usually snip it and land the low beam side of the jumper to that main distribution bolt right next to it with a ring terminal. Easy.