Planter91C2

Last year my speedometer went out, removed it and sent for rebuilding. Rebuilder confirmed he fixed it and was working. Installed and it didn’t work, investigation led me to the ABS relay. I replaced it and drove for a few thousand miles last year. Put car in storage for winter, removed battery. Last week, go and get the car out of storage, install battery, fires right up. Everything working for about a 20 min drive home. Pull in to garage, attach a float charger to battery as it’s not driven a lot. 1 week later, disconnect the float charger, fire up the car and hear the ABS warning screech and light on the dash. Drive out and speedo not working again.

any ideas? What would kill abs sensors? Could the original speedo problem cause any downstream issues? Speedo smoked and filled cabin with small amount of electric smell, but that was repaired as the speedo guy showed me the pics of the fried board he raplaced.

ToreB

This may well be caused by a defective or incompatible charger. I generally do not recommend connecting a charger while the battery is connected to the car. Voltage spikes when connecting/disconnecting the charger leads, as well as during the charging process, may damage the internal overvoltage protection in the various in-car devices.
In this case, I would recommend to start with checking for any fault codes stored in the ABS control unit. However, only the C4 has OBD capability, fault finding in the C2 ABS system needs manual measurements.
Cheers,
Tore

Planter91C2

Thank You

without the ability to diagnose manual measurements, do you think I should buy another ABS relay and never use the float charger?

they are not cheap

No_snivelling

By installing a battery isolator switch you can then safely attach and disconnect your float charger without any fear of damage.

But what I found was the main benefit of the isolator switch was that a float charger was not needed even if the car sat for months at a time. By being isolated, there is zero load on the battery.

Peteinjp

I put a trickle charger on my car all the time with no issues as I don’t want to have to a system adaptation.

Pete

No_snivelling

Fair point. My rough idle smooths out after a 15 minute drive as the car adapts on its own.

Planter91C2

I heard on pelican that there is a Mercedes abs relay that works and is less expensive, anyone ever hear of that?