Starfollower

Hi - Even though I have a 2003 CL600TT, this forum page has always helped me more. Sometimes my key will not lock or unlock my car and every now and then it will not work in the ignition (won't turn). This happens especially when engine hasn't been started for a while. Makes me too scared to use this beautiful Merc.
I have a brand new key and both keys have new batteries - the red light does flash when used, so I don't think the fault is with the key?
Does one system control both these functions. Any help appreciated ... cheers .. Eddy in NZ

wallyp

I know nothing at all about the CL600TT, so, not being hampered by facts, I can discuss the subject freely...

If this were a w220, I would say:
The batteries in the keys have nothing whatsoever to do with starting the car. They are only for the RF system (which is mainly for locking/unlocking.the doors and hood and setting the alarm) and for the IR system (which is used opening/closing the windows and sunroof from outside the car).
The starting function is done thru the IR system, but for this purpose, the IR system is powered by induction coils in the key and the EIS, not the batteries in the keys.
One of the first suspicions for your problem is the battery. The W220 is extremely critical on battery voltage and amperage, and a weak battery or poor battery connections can and will cause problems.

Kebowers47

It sounds as if the vehicle battery voltage is decaying when the vehicle is sitting a few days. This can be caused by a 'parasitic drain' from a module not 'shutting off' or the battery itself may be failing. If possible, next time this happens, check the vehicle battery voltage before attempting to open and start. Then have the battery load tested at an auto parts store. Car batteries DO wear-out and slowly develop internal 'voltage leaks' . Another way to check the battery is to measure the strength of the sulfuric acid in each cell of the battery with a hydrometer. The hydrometer reading should be nearly identical in all 6 cells. and above 1240, ideally 1250-1260. A significand difference (more than 0010) is abnormal and indicates that cell is partially 'sulfated' and not taking a full charge. Many times this 'sulfation' can be corrected by a long, slow charge (several days) to de-sulfate the battery, converting the very hard lead and black looking sulfate back to sulfuric acid and white lead oxide. A 'quick charge' can cause the lead sulfate to crack and fall off the active lead, permanently reducing bettery capacity or even causing battery to fail by flaked off lead sulfate bridging the gap separating the 'oxide' and 'sulfate' plates and causing a short circuit (and death of the battery)

Then test for a parasitic battery drain.

Starfollower

Thanks for your reply - I do keep the car on a 'maintenance' charger when garaged . Would this rule out the battery? I will get it checked though as the W215 coupe also has numerous things that need good battery feeds.