ABS not working

[Dlb26]

Hi
Not had my E30 long, bought it as a rolling restoration and today decided to delve into why ABS light doesn't come on let alone go off again and the bodge that is the wiring. It is a 1988 325i switchable auto, runs, drives and has MOT.
Protection relay had blown but obviously that puts light on and I don't even have that, repaired with soldering fuse fix anyway.
I have taken instruments out, put in new bulb to be sure still nothing.
Went on to check power to system. Pin 20 on C101 connector out of the fuse box had no connector or wire, The other side has the red/yellow wire which I assume is the same wire going to relay on top of unit.
Obviously I don't know what bodges have gone before but I believe engine has been changed at some point.
So is my next step to wire from DME relay to pin 20 and see what happens? But can't understand why PO wouldn't have done the same.
Any advice most welcome and appreciated.

[Brianmoooore]

Earlier ABS system gets its ignition switched power from the infamous silver voltage protection relay behind the glovebox. The later version dispenses with this relay and taps ignition switched power off of the DME relay instead.
If your car has the voltage protection relay, which I think you infer it has, then there won't be a red/yellow wire on pin 20 of the body side of the C101, and any red/yellow wire on pin 20 of the engine loom side will be irrelevant.
It's unusual for the warning light to not illuminate when the ignition is turned on, if there is a known good bulb fitted in the holder.
The wires to this bulb should be green and either green/red or grey/red. The green wire should have 12 volts + on it when the ignition is on, as should the other wire if the bulb isn't lit.
Check that the 12 volts + is present, and that the wires actually go to the ABS ECU.
If you disconnect the ABS ECU and turn the ignition on, earthing the grey/red or green/red on pin 29 of the plug should make the bulb light.

[Dlb26]

thanks for that. Now that I've read a bit more on the wiki I'm going with my car has had a newer engine fitted hence the red and yellow wire in the engine side of the c101. The warning light does have green and grey/red wires to it. I'll try the checks you mention and report back, hopefully tomorrow but I've got the pleasure of a niece's birthday to attend.

[Dlb26]

Managed to squeeze in an hour's work and pleased to report light comes on and goes out when I start the car. I haven't driven it yet to see if it stays off but at least that will be wheel sensor issue if it happens.
Took gauges out again (I've got that down to a matter of minutes done a few times already) and took abs bulb out of housing. Turned on ignition and light lit straight up! First thoughts was an elaborate mot hide with a cover over inside of symbol but no, separated gauges and could see daylight through the abs "window". I can only assume the pressure of being a tight fit in the casing was causing it to not light as I have reassembled with the holder in just enough to stay in and hey presto.

Thanks for your help Brian, was starting to get frustrated with it for a while.

[Brianmoooore]

First thoughts was an elaborate mot hide

MOT 'hide' is just to solder the wires across the oil pressure or battery warning light. Faulty sensors also do not show in a MOT test, since there's no road test element in the test.

[aimlessrock]

I was having an ABS issue with my cabby after the resto (mine is the later type with the relay on the pump). I checked everything and could not find any issues, but the light would not go off.

I took it for a short drive and the light went straight off and has been find since. Only conclusion i could come up with was the sensors needed to detect the motion on the rings?

In this scenario the car was rebuilt from almost a bare shell.

Hope it helps

[Brianmoooore]

All E30 ABS pumps have two relays - the update is to replace a voltage protection relay (mounted above the glovebox) by the DME relay, which is fitted anyway, as part of the engine management.
The ABS diagnostics don't look for signals from the sensors, or check them in any way, until the ABS ECU detects that the car is moving above a certain speed, determined by the signal from any of the ABS sensors. It then checks that all four signals are present, and turns the light on if they're not.
I've no idea why your light stayed on after start up, but iof it's behaving now, Ishouldn't worry about it.

[Dlb26]

Well took the car for a run and the light stayed off after starting and driving. Very pleased and to be honest pleasantly surprised.
Thanks again for the help.