1990 500 SEL ABS light on when driving

Dutchmanbob

New Member
Joined
May 28, 2020
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11
Location
Enniskillen N-Ireland
Car
1990 500 SEL
My 1990 500 SEL . ABS light is off when starting the car. The ABS light comes on, once the car starts moving, indicating it is a wheel sensor problem, I think? I had the sensors checked and all three are giving correct readings. Anybody have any advice on what I should do next?
 

alabbasi

MB Enthusiast
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Feb 18, 2008
Messages
1,886
What's your idle look like? if you have high idle and ABS warning light. It's likely the OVP relay.
 
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Dutchmanbob

Dutchmanbob

New Member
Joined
May 28, 2020
Messages
11
Location
Enniskillen N-Ireland
Car
1990 500 SEL
Hi, Idle is fine. Engine runs perfect. No ABS light on when starting and revving the engine. It comes on when you start driving over 5 miles an hour
 

Pontoneer

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Aug 19, 2002
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15,114
Location
Central Scotland
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'99 S320 W140
I had that with my 500SEL , the wires become brittle with age and can make/break connection with movement of the suspension, yet give an OK reading while on test in a workshop ( on a rolling road ) . I had both front sensors replaced and the problem was solved .

You could try picking up a pair of used sensors and swapping them yourself ( hardest part is getting the bolts undone as they tend to rust up ) it isn’t otherwise a hard job at all . Also clean up the coaxial connectors where they plug in as these can get dirty .
 
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Dutchmanbob

Dutchmanbob

New Member
Joined
May 28, 2020
Messages
11
Location
Enniskillen N-Ireland
Car
1990 500 SEL
I had that with my 500SEL , the wires become brittle with age and can make/break connection with movement of the suspension, yet give an OK reading while on test in a workshop ( on a rolling road ) . I had both front sensors replaced and the problem was solved .

You could try picking up a pair of used sensors and swapping them yourself ( hardest part is getting the bolts undone as they tend to rust up ) it isn’t otherwise a hard job at all . Also clean up the coaxial connectors where they plug in as these can get dirty .
Thanks for that! I think i'll try and get a used pair and try a swap.
 

Pontoneer

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Joined
Aug 19, 2002
Messages
15,114
Location
Central Scotland
Car
'99 S320 W140
Would you still have the parts number of yours?
Sadly , no . I had three W126s but the last one went eight or nine years ago .

I put the car into a specialist to diagnose the fault , and the total bill was something like £280 for diagnosis, two new sensors at around £120 each and fitting , quite reasonable given most of it was parts .

The sensors are left and right handed , so two different parts .
 
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Dutchmanbob

Dutchmanbob

New Member
Joined
May 28, 2020
Messages
11
Location
Enniskillen N-Ireland
Car
1990 500 SEL
Think I might get mine checked with a specialist in electrics next. Thanks for your help!
 

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