W124 Coupe - where's the rear ABS connector ?

[franksm]

Hi folks

Long-time lurker, needing some help

The ABS lamp on my W124 coupe comes on when the car is going > 50mph, or when driving in the wet. I have checked the wiring for the front sensors and they seem fine; have not removed them to clean them yet (since their bolts need renewed if disturbed).

Have tried to check the rear sensor (in the diff) but can't find where it connects under the back seat - am I looking in the right place, or does the ABS cable run externally under the car ?

Also, is there any way to query the ABS unit, get flash codes, etc ?

Cheers

Frank

1992 W124 230CE (100,000 miles) http://mx5ireland.com/members/frank/benz/DSC05805sm.JPG
1996 Mazda MX5 Turbo (120,000 miles)
1973 MG BGT (110,000 miles)

 

[Silver Arrow]

In mine, it's under the rear seat. (Along with coins etc.)

 

[franksm]

nearside or offside ? nearside on mine has the "comfort control" box aka the electric windows & door locking computer; offside has what might be the vacuum pump. Can't see anything that looks like coaxial cable from the sensor.

Unless you mean under the centre of the seat, the arm-rest area ?

 

[type49]

It needs a high speed to get the light on, this would usually indicate a sensor problem. Sounds daft but have you recently had tyres fitted & maybe wrong size, making a wheel turn at the wrong speed? From memory, the rear sensor connector IS under the rear seat, OS.

 

[franksm]

Cheers - will have a better look offside... but... well, fingers crossed.

I have 17" rims with 40 profile tyres on the front and 45 profile on the rear - car has that "jacked up" look. Not my choice (previous owner) but when I asked the local tyre company about putting 45's on the front, they said they would foul the bumper :-( which would be expensive.

Check my pic and you'll see what I mean.

Different tyre size might be a reason right 'nuff, but there's the odd time when the ABS light comes on when the car is sat still. I think what I might do is to remove the sensors for cleaning, and just use threadlock when bolting them back in.

 

[shj]

Changeing the subject (sorry) what tail pipes do you have on your CE

 

[franksm]

says "Powerflow" on them (which can only be a good thing ) and in the history file I see an invoice from Powerflow, the chain of shops that make stainless exhaust systems

http://www.powerflowexhausts.net/faqs.cfm

It makes a nice noise - nice thrumm off it, but not booming or raspy. Suits the car.

From what I know of Powerflow, they have a large stock of generic stainless pipes and silencers/resonators, and can mate them to any car.

 

[type49]

What are your exact tyre sizes front n rear. Also when the ABS light comes on, does the engine idle change? There is a relay that's common to both.

 

[franksm]

Car's not here with me, but from memory 215x40x17 on the front and 225x45x17 on the rear

Yeah, when the ABS lamp switches on and then off while the car is idle, foot on the pedal, there's a "kick" in the pedal, and the idle does change. I figured that was because the ABS system saw the problem go away, extinguished the lamp, and re-enabled the ABS pump - hence the kick.

 

[television]

just a thought here, though modern engines and ABS runs off the alternator the cause could be the OVP relay, have there been any variations in the idle speed.

Malcolm

 

[type49]

Does sound like OVP relay, although your tyres are 30mm difference in diameter which does help. Remove the plastic cover to expose the battery. to one side of the batteryyou will see a tall, silver relay with a red top ( it may have a black covering over it ) On the top is a red 10 amp fuse. ( It may have 2 fuses ) Check fuse & replace if ness. It could still be a faulty relay itself even if the fuse is OK.

 

[television]

I dismissed the tyres as the fault is there on starting up.

Your car is a bad year for poor wiring harness troubles along with the fuse holders. If the speed of the engine changes when in idle when the ABS lamp comes on the OVP relay could be dry jointed,a common problem.

Malcolm

 

[franksm]

I'll take the OVP relay apart next weekend, and have a looksee. I guess a dry joint or broken solder will show up as discoloured. There is indeed a fuse on top, but it looks fine.

Thanks lads, will let you know how I get on

 

[wireman]

I think the abs sensor on my 124 250D 1989 is on the nose of the diff under the back end car, otherwise it would not be sensing the rotation or non rotation of anything .