1991 with Cruise COntrol and ASR issue resolution

[abaird]

Hi I have a 1991 R129 500SL with Cruise control.

The ASR light came on after about 5 minutes and car went into Safe mode, although sometimes it would just go straight into Safe mode:

However:
1: When Cruise control switched on this didn't happen ie it didn't go into Safe Mode
2: Though when in Cruise control after 10-15 minuets Cruise stopped working, and ASR light on and car goes into Safe Mode. If car restarted then worked again

My Mechanic suggested to remove the Link ARM links the Cruise control to throttle linkage. When we did this car works as normal BUT the ASR light is on permanently, and of course no Cruise control

I'm aware of the dreaded ASR light and how difficult it is to identify the issue and fix SO has anyone actual (vs theory) fixes that they have used for same; eg:

1. Is it a simple case of the Cruise control unit is broken get a new one and ASR light goes and car works as normal OR ?
2. IS it just another ASR symptom and not actually related to the Cruise control... In which case am I best ot leave as is and remove the ASR bulb !! ?
3. Other outcomes

Thanks Andrew

 

[Pontoneer]

I'd think dirty/corroded reluctor rings or ABS sensors would be a good place to start - both of these systems depend on them , and giving them a good clean will do no harm . If you have any other electrical gremlins then OVP relay can throw up a surprising amount of faults .The R129 is basically a W124 under the skin , so all the faults that affect them can manifest on R129/W140 , both of which are closely related .

 

[abaird]

Thanks I’ll start there and comeback