Apologies - another 190e ABS light issue

e36t

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1991 190E 2.6/3.0, 1989 500SE
This all refers to a 190E 2.6 (fitted with a 3.0 bottom end)

I was having some problems with the alternator - no other issues other than low charging - so pulled it from my car to check the brushes. They are well-worn but just about serviceable - good enough for now, but a note to self to sort soon.

Replaced the alternator, and now the ABS light comes on with the ignition, and stays on. Sometimes, especially when driving at night, all the dash lights will glow dimly. Very pretty, but so wrong. This is intermittent - it is not consistent and doesn't seem to follow any pattern.

The ABS light is a constant - on and shining brightly. Sometimes it may go off for a half-second when starting, but then come back on.

However, if I am driving and select neutral, switch off the engine and coast briefly, then switch the engine back on (while coasting) the engine starts and the ABS light stays off. Hurrah! Not much use for vehicle inspections, unfortunately.

First thought was low voltage output from the alternator at start up, so I stepped up the sorting program, and got hold of a second, known good alternator.

In the meantime I've read that if a diode pack in the alternator gives up, it can have this effect.

Repacement alternator fitted (think I need a new belt tensioner :roll: ) and... ABS light is still on. So much hassle for a thought sure-fire fix, but no.

In fairness, the replacement alternator is slightly smaller than the original - 14V 70A vs 14V 80A. I don't think this will make a difference in daylight driving, and is unlikely to be an issue after dark.

I've replaced the OVP relay, checked the fuses in the old and new ones - no problems.

OK... Suggestions? I think I have experienced a very unfortunate coincidence, unless there is an ABS fuse somewhere and somehow that's blown.

Please help!
 
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Bolide

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I'd check the wiring to the base of the OVP socket

Nick Froome
 

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mmm------ broken or poor engine earth strap or alternator earthing . Buying "known good " alternators second hand is a false economy when you can buy a reconditioned unit [ with a warranty] on exchange. why didn't you just renew the alternator brush and regulator pack?
[YOUTUBE]WYvZRz5Truo[/YOUTUBE]
 

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Poor ground somewhere,, what is the running voltage now
 

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Do check the OVP relay fuse on the top
 
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e36t

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I'll check the OVP relay again. Mine is the type with two fuses on top - I did a visual inspection on the fuses on two relays, and have tried both relays.

To reiterate - there was no problem until I tried to be clever with the alternator. Coincidence, or is there something I've overlooked?

Rebuilding the alternator looks like a bugg... devil of a job. I got part of it apart, but to go further was a definite get your soldering iron out job.

As I'm in NZ, we tend to grab whatever is available. The replacement alternator was actually a gift from a friend in the US - I'm very grateful to him for that, the leads, dizzy cap, rotor arm, f&r W124 400E brake calipers, brake pads, discs and much more.

So I have a working alternator on the car, and will get the removed one refurbished. Over here, that's at least a $250 job - £125, but at least it can be done at leisure now. Perhaps I will have a go.

Need to measure the voltage - pd across the battery, or somewhere else?

Thanks. :)
 
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e36t

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Do check the OVP relay fuse on the top

Checked the fuses in the top of both OVP relays I have here. One relay 'rattles' a little if gently shaken, the other doesn't. Makes no difference (as far as I can tell) but the non-rattly one is currently fitted.

I'd check the wiring to the base of the OVP socket

Nick Froome

Not checked that yet. Trying the easier-to-get-to bits first... When checking the OVP relay would probably have been a good time, but the weather chose that moment to get unpleasant, blowing clouds of rain in the front door of the garage. :(

Poor ground somewhere,, what is the running voltage now

I checked it just now, but still may not get the figures exact! Across the battery, voltage with engine off is 12.36V, with engine running it is 14.2-something volts, not quite 2V more.

Graham
 
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e36t

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That's interesting - thank you.

Makes some sense, too. The ABS requires (I think) more than 10.5V to function.

OK. The diagram says behind battery, and describes the alternator as being on the right side of the engine; presumably the alternator location is as seen from the drivers' seat. But is the ABS control unit referred to going to be the one mounted near the inner wing (passenger side for the UK, OZ and NZ), or is it referring to something else?

I've had the battery in and out a few times now, normally to check the OVP relay. Perhaps I have 'upset' something...
 

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Diagrams do refer to as from the drivers seat, I wonder if the ABS ecu is fried
 
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e36t

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Diagrams do refer to as from the drivers seat, I wonder if the ABS ecu is fried

Awww.... Feck. Or something like that. you know what I mean. No easy way to test other than by trying a known good one?

Something I've just remembered - another symptom. Having driven the car with the ABS light showing, gone through the coasting, engine off, engine on procedure in order to 'switch off' the warning bulb, I sometimes feel a juddering through the brake pedal while stationery at a junction but with my foot on the brake. It feels similar to the way the pedal feels if you hit the brakes too hard on ice (when the ABS is working correctly).
 

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There are loads of spare parts around for these now days and most do shipping


You could try the 190 forum
 
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e36t

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There are loads of spare parts around for these now days and most do shipping


You could try the 190 forum

You're right, of course. Unfortunately my location and time are against me.
There's one on eBay for US$30. Plus US$40 shipping. And delivery in about two weeks.
I'll see what I can find here, or possibly in Oz.

Thanks.
 
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e36t

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I'll pull and clean the sensors tomorrow. I've replaced the rear ARB for something a little stiffer, which required removing the ABS sensor from the diff. It did work perfectly well for quite some time, but maybe there's something there.
 

Gary Hanson

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However, if I am driving and select neutral, switch off the engine and coast briefly, then switch the engine back on (while coasting) the engine starts and the ABS light stays off. Hurrah! Not much use for vehicle inspections, unfortunately.
I had a similar thing happen on a 91 model volvo 940. Luckily it had just passed an MOT, but I didn't like the car having inoperative ABS.
ABS light came on whilst driving. Switched off engine, restarted it. Seemed to reset ABS and light stayed off. Gently braked the vehicle to a stop, noting which direction it pulled. Then replaced the sensor on the opposite side to where it was pulling.

If it pulls left, it suggests that the right hand sensor is wrongly detecting a lock up and releasing braking effort to that wheel. If it pulls to the right, suspect the left hand sensor.
That's how I tested mine. Then I tried a second hand sensor and it cured the problem.
 
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e36t

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Thanks Gary.

Unfortunately, there is no pulling. There is wear on the discs and pads, but certainly not to the point where you'd ever consider changing them. The brakes work perfectly - hands off the wheel and gentle or even firm braking sees the car stop straight and true.

With the ABS light on, the ABS isn't working. At present, that is the only thing I can find wrong!

The only time there is anything untoward is after I have gone through the coast, shut down, restart procedure and the ABS light stays off, and then stop at a junction with my foot on the brake. Then, while stationery sometimes there is a judder through the pedal as though the ABS is activating.

:confused:
 
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e36t

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G;Day; Where Abouts in Auckland are you !

Hi Maska,

We're near Clevedon. Kinda moved here almost by accident - nice area, rent is a little pricey but not too bad, just a little out of the way from everywhere else.

How about you?
 
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e36t

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Anyone know if the ABS pressure regulator relay, p/n 0015426719, could cause this sort of problem?
It is at least a lot cheaper than the ABS ecu!
 

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