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99 cl500 starter/battery warm start problem

3977 Views 10 Replies 7 Participants Last post by  syljua
I should start by saying I’m in love with Ruby! The ride, the power, the grace of this car is amazing.

I’ve spent some serious money at the MB dealer, rear struts, actuators, brakes, rotors, tires, starter, battery, oil pressure sending unit, central locking pump, and last but not least a complete service.

So here is the problem. When she’s cold the engine turns over fast and starts immediately. On short trips she starts right up, no change.
On a longer trip, the car running perfectly, oil pressure and engine temp normal, the battery seems dead when engaging the starter. The engine will barely turn over, service and warning lights go dim, try again and you even hear the tick of what sounds like a completely dead battery.
The first time this happened the dealer said it was the starter and I had it replaced. At the same time we replaced the battery with an almost new one.
I had no problems for a month or so (keep in mind my trips were short around town). Yesterday I drove the car 100 miles, AC on everything working perfect. Turned her off, turned the key on and the engine barely turned over, tried again, completely dead.
I went to my appointment and returned an hour later. The engine turned over very slow but started.
Drove home, again, 100 miles no problems, half the trip at night.

The next morning the car turned over like a highly charged battery. After a 30 minute trip with two very slow starts in between the battery went completely dead again. AAA used a battery pack to jump the car.

I had the MB dealer bring a new battery out. First he tested the battery and said it was good, and then a re-test showed bad. He went ahead and put the new battery in and the engine turned over fast and started. He let the car idle for about 20 minutes, turned it off, same thing, engine wouldn’t turn over.

What should I be looking at?


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Benz4mm first of all go and buy yourself a simple multimeter (for like $15 or even less) to test the voltage on the battery yourself (rather then buying new batteries or calling dealer over to "check" it) then check the voltage of the battery and it should be somewhere around 12V+ (possibly around 12.5V or so if not something is draining your battery or its not being charged enough) then check the voltage when car is running it should be around 14V (if its any less then your alternator isnt charging properly - could be several issues like voltage regulator etc.)

Let us know your findings, depending on that we can provide you more help from there....

This will do: (btw there is always manual on how to use it but if you get stuck i can help its very easy just one knob to turn the right setting and two leads for +/-)

PORTABLE ELENCO M-1000B DIGITAL MULTIMETER 100% WORKING - eBay (item 280229003681 end time May-27-08 18:46:49 PDT)
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Hold your horses i think you are getting bit too complicated for start he should check basics just to make sure his car is even charging the battery as it should, and then go from there...
W140 are common for having failing voltage regulators on the alternator and its a cheap $35 part so no need to replace whole alternator just yet....
Should be like mine, if i do the same here with my 500SEL, when car is running iam gettin close to 14V with car off iam getting bit over 12V (and i have crappy battery anyway) so yes were are onto something...your alternator is not charging to the full potential, either worn or MOST likely voltage regulator! (do a search on this site and there are several discussions about it)

part is here for $27

Your Parts Search Returned 0 Part(s)

and i belive your alternator can stay in a car to replace the regulator...its just bit of pain getting to it
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