E200 auto, gear change from 5 to 4 in crusing

[MikeG]

Hi all, just joined the forum and have a question to ask. I have a 96 E200 saloon auto and recently noticed that when crusing at 70 the gear goes down from 5th to 4th. This happens for no apparent reason, ie a level road and no chnage in acceleration.

Any ideas?

Mike

PS just got the car serviced at the dealers, still the same

 

[television]

Miles

How many miles has the car been ?
The fault will be recorded in the data system, have a fault code check.

Malcolm

 

[MikeG]

Hi Malcolm, its done 120,000 miles the fault is quite recent. One thing I have noticed: it only happens at night! The only difference is that the lights are on. I have also noticed that the battery(not replaced yet) voltage is slightly low, when I start the car in the morning, then its OK. Could that have anything to do with it?

Mike

 

[television]

Not easy to answer. Your car will not be happy running on a poor battery. Mercs 94-5>Do funny things when the voltage drops below 12v. The nomal running voltage is 13.8
11volt is the limit where things start stopping or fail to work.
Some later Mercs have a very clever damper on the front of the crankshaft, when the engine is stopped it leaves the timming in the retarted mode, that makes them very easy to start with a poor battery,as soon as the oil presure builds up it advances the engine to normal. Malcolm