The problem started during the very hot, humid weather. First time, tried jumping battery and did not start. After sitting for 2 hours, it started and I replaced the battery. Two weeks later, same thing. Let it sit for three hours, then it started. Next afternoon, had not been driven, would not start but everything works in car. I had it towed to dealership, has been there almost two weeks. They think it is ignition because they can't find anything else wrong. They said repair will be expensive and I still have my doubts about diagnosis.
Any suggestions?

 

you mean it won't crank?

if you insert the key to the EIS, can you feel the usual engagement of the steering lock release?

when the problem is present, the remote key can lock and unlock the door? can you see the red LED flashing on the key?

i think your EIS goes into sleep mode and cannot get the wake-up signal.

 

Sounds like a crank position sensor to me. When the sensor gets hot, it will tend to go open and not read a value. Once the car cools down again and so does the sensor, then it starts.

 

See my post on 8/26 S430 Starting problem. Seems to be a MB problem. Dont let the MB dealer change the ignition switch unless you have $400 dollars you dont need.
My 430 has the identical problem however it is not heat related. It just happens whenever it feels like it. In the garage, at my wifes work, the grocery store, etc.

 

5 weeks, and a few days later, we have the vehicle back. Dealer relieved us of nearly $500 and replaced the EIS. (Charging us only for the labor!) The vehicle starts, two weeks ago it was "ready", upon picking up the vehicle I noticed that my instrument cluster was not functioning. The dealer then told me that the instrument cluster was no longer communicating with the new EIS. A new instrument cluster and we're good to go. The cluster was supposed to be $1,600, but MB agreed to eat the cost of the cluster. The car is running, and does start, but they forgot to program the cell phone as an option, and did not program both of our keys. Tomorrow morning, back to the dealer to handle the details. Fingers crossed the problem is solved.

 

Glad to hear they have finally seemingly fixed your problem. Doesnt it really gall you that the dealer didnt even bother to check that the other functions were not working. Instrument cluster inop? Seems that may have been somewhat obvious. Didnt program the keys?? Nice that they are will willing to absorb the $1600 cost. They must have damaged it in the process of replacing the module.
Unbelievable that a dealership could be so inept. I would expect something like that from "Joe Schlock" on the corner but MB should be above that. My wife's MB was the first deviation from Lexus in years(against my judgement) and it looks like we are headed back to Lexus soon.
Hope it keeps starting!!

 

My problem turned out to be the starter relay. Only took 6 months but dealer found it. We gave them the vehicle and told them to drive it until it failed. Took two days but it failed and they were able to analyze it.