Switching on headlights switches on radio

[bmwe30mtech]

Hi all,

I have an electrical issue on my stock 1989 325i. The issue has always existed since I bought the car.

When I switch on the lights (ie pull out the main front/rear light switch), my radio is switched on too. Switching off my lights switches off the radio.

I can switch on/off my radio as normal using the switch on the radio too.

My car has the original dealer-fit stereo loom fitted, and a Blaupunkt SQR 88 radio. The loom plugs into the 4 pin socket in the accessory socket, and is uncut.

The wiring is connected as:

Permanent live = red/green
Ignition switched live = purple/white
Earth = brown
Radio panel illumination = red/grey

The car has an electric aerial, with the red wire connected to permanent live and white wire connected to the red/grey panel illumination. If I disconnect the electric aerial, the issue with the lights switching on the radio persists, so I don’t think this is the cause.

Does this wiring sound correct? If not, please could somebody point out the error?

Picture of the wiring attached.

Thanks,
Paul

[fixedwheelnut]

Hi all,

I have an electrical issue on my stock 1989 325i. The issue has always existed since I bought the car.

When I switch on the lights (ie pull out the main front/rear light switch), my radio is switched on too. Switching off my lights switches off the radio.

I can switch on/off my radio as normal using the switch on the radio too.

My car has the original dealer-fit stereo loom fitted, and a Blaupunkt SQR 88 radio. The loom plugs into the 4 pin socket in the accessory socket, and is uncut.

The wiring is connected as:

Permanent live = red/green
Ignition switched live = purple/white
Earth = brown
Radio panel illumination = red/grey

The car has an electric aerial, with the red wire connected to permanent live and white wire connected to the red/grey panel illumination. If I disconnect the electric aerial, the issue with the lights switching on the radio persists, so I don’t think this is the cause.

Does this wiring sound correct? If not, please could somebody point out the error?

Picture of the wiring attached.

Thanks,
Paul

Disconnect the white electric aerial wire from the dash illumination grey/red wire that will be the cause. when you switch the lights on that is putting a feed on the white wire which normally only gets a feed once the radio is on so it is back feeding the radio supply.

Or that grey / red wire is connected to the wrong connection at the rear of the radio.

The white wire from the aerial should be connected to the blue accessory power output from the radio, if the radio does not have one connect it either to an ignition feed or a separate switched feed.

[bmwe30mtech]

Thanks for the reply. I have tried disconnecting the white aerial cable, and the aerial therefore doesn’t go up anymore, but putting on the lights still switches on the radio.

I’ve checked the wiring diagram printed on the outside of the stereo unit and I’m fairly certain the four wires are connected the right way.

[Contours]

Would wonder if your radio is connected up to the parking lamp/interior light circuit which on my car are fuses 22 and 23. If you pull these fuses, does your radio come on when you pull the light switch. There is a wire running across under the dash to the light switch from these fuses which are live when you pull the switch.

[fixedwheelnut]

Thanks for the reply. I have tried disconnecting the white aerial cable, and the aerial therefore doesn’t go up anymore, but putting on the lights still switches on the radio.

I’ve checked the wiring diagram printed on the outside of the stereo unit and I’m fairly certain the four wires are connected the right way.

Disconnect the illumination wire from the radio and try it, connect the white wire to the same terminal you disconnected the illumination wire from.


Can you get a photo showing all the terminals on the rear of the radio plug, also what radio is it?

[bmwe30mtech]

Thanks for the responses.

I’ve tried disconnecting the illumination wire from the back of the stereo, and this solves the problem, ie turning on my lights no longer turns on the radio (it turns out that switching on my radio was also switching on my dash lights). The white wire to the electric aerial was also connected to this wire, so that no long goes up.

The stereo is a Blaupunkt Memphis SQR 88. With the illumination wire disconnected, the radio only lights up when switched on. Is this correct, or should the radio light up when the dash lights are switched on?

Assuming I leave the illumination wire disconnected, where should I wire the white electric aerial wire to, so that it goes up when I switch the stereo on?

Thanks

[flybynite]

My original Blaupunkt radio is a bit older than yours but it only lights up when switched on.

On mine there are 4 power connections - 2 large for IGN live and earth and 2 smaller for HOT live and switched output for aerial. nothing else other than speaker outputs.

[fixedwheelnut]

Thanks for the responses.

I’ve tried disconnecting the illumination wire from the back of the stereo, and this solves the problem, ie turning on my lights no longer turns on the radio (it turns out that switching on my radio was also switching on my dash lights). The white wire to the electric aerial was also connected to this wire, so that no long goes up.

The stereo is a Blaupunkt Memphis SQR 88. With the illumination wire disconnected, the radio only lights up when switched on. Is this correct, or should the radio light up when the dash lights are switched on?

Assuming I leave the illumination wire disconnected, where should I wire the white electric aerial wire to, so that it goes up when I switch the stereo on?

Thanks

I don't think the Memphis had illumination having googled it, it looks like you have a very early style plug on the back, a bit like below, if you get a photo of the rear wiring connections we can help better.

[bmwe30mtech]

Thanks again. I did post a picture of the wires from the back of my stereo in the first post. Does it not appear on your screen? I’ll try again here:

Perhaps I just need to unplug the illumination cable. If I do, where should I connect the white wire of the electric aerial, so it raises when I switch on the stereo?

Thanks

[DaniTD]

Thanks again. I did post a picture of the wires from the back of my stereo in the first post. Does it not appear on your screen? I’ll try again here:

FEB2EA77-A157-46E4-8F88-F22A3DD312A2.jpeg

Perhaps I just need to unplug the illumination cable. If I do, where should I connect the white wire of the electric aerial, so it raises when I switch on the stereo?

Thanks

I think that little pigtail that connects the main loom to the radio via 2 wires is modified. As you have it now, it makes no sense. Those two cables from the main loom provide permanent 12V for station memory (red/green) and light switch 12V for illuminated radio front panels (grey/red), when necessary. The white cable shouldn´t be connected to the grey/red cable.



Probably upon close inspection, that pigtail was nicely modified when someone tried to install the Blaupunkt. My theory is, in some E30 schematics, the aerial control cable is marked as white, and the cable that connects some stereo's light input is marked also white, so it got misunderstood.

Having said that, what I would do is the following:
-The SQR 88 doesn't have light input, it always has its faceplate illuminated
-Disconnect the grey/red cable from the radio, since that pin is used on the SQR88 as aerial output signal and that way you are backfeeding power between lights and radio
-Cut or desolder the white cable at the pigtail, crimp some spade connector, and connect it where you have now the red/grey cable connected

Keep that Blaupunkt power unit, it is a real banger and one of the most powerful period correct stereos. And fan cooled

[biffer]

Dan's right

[fixedwheelnut]

Thanks again. I did post a picture of the wires from the back of my stereo in the first post. Does it not appear on your screen? I’ll try again here:

FEB2EA77-A157-46E4-8F88-F22A3DD312A2.jpeg

Perhaps I just need to unplug the illumination cable. If I do, where should I connect the white wire of the electric aerial, so it raises when I switch on the stereo?

Thanks

Yes I could see that, I meant take a photo looking in to the plug of the radio so we can see the pins.

Also DaniTD has it prettymuch on the money

[bmwe30mtech]

Thanks very much all for the responses.

Dan was correct, and it’s now fixed and working correctly, thanks. The modification to the plug to include the white wire was made by me, several years ago. So in short I had connected the electric aerial to the correct socket on the radio, but should not have connected it via the illumination wire. I’ve neatly made the correction!

Thanks all,
Paul