I need some technical expert to help me to trouble my car probem: The battery is full charge with 12.7 Vdc I checked. I turn the ignition key with the gear in Parking postion (Auto Transmission). I see all the instrument is bright displayed. However I notice the starter is not cranking at all.
I guess two possible probem. Either the key when turn to start position is not working or the starter is not working.
I would to know someone help me to make a jumper to ignition key contacts to see the problem of the ignition key or the starter?
I do not mind go to buy the key and the starter and replace both and try to see it fix.
However it is rare to have both ignition key and starter going out at the same time.
I deperate need some advice for troubleshooting steps.

Thanks

 

You don't say what type of Mercedes you have, but this general answer might help.

If your key turns easily in the ignition lock then your lock is OK. Do you have to "jiggle" the key to get it to turn? If so you will need a new lock. The lock is a seperate item from your switch that the key turns, by the way. Ignition switches rarely go bad, but when it is time to replace the ignition lock you are a fool to not replace the switch at the same time.

Do you have an automatic transmission? It is likely your "Neutral Safey Switch" is bad. Your car must be in Neutral or Park in order for the current from the igniton switch to reach the starter relay. These do go bad and must not only be replaced but must also be adjusted. It is not uncommon for one of the wires to fall out of the switch as well. This should be done by a real mechanic as replacing the switch is not hard but adjusting it can be tricky.

Try moving your shift lever back and forth a bit while trying to start the car. Keep your foot on the brake while doing this as the car might jump if you drop it into gear. If the motor turns over then it is your safety switch. The safety switch is located on the left side of the transmission and is very hard to get at. If you can see it then look for any loose wires hanging from it as that could be your problem.

You can remove the starter and have it tested at many auto parts stores. I don't know how easy it would be to remove, but once out of the car it is very easy to test.

You might be able to have this repaired at a automotive electrical repair shop cheaper than any Mercedes place.

Sam

 

I am aprreciate of your advice. My car is Mercedes Benz 86 560SL with Automatic transmission. These are steps I did try but the car starter wil not crank.
1. I put the transmission shift to Neutral and Park. Starter not craking in either case.

2. I check the wires to starter. Two wires are looks good. I check the voltage from big wire to chassis ground it read +12.7 VDC. I check the small wire to GND. It has good ground.

3. I make a jumper from small connector of starter to +12VDC. Turn the ignition key to ON position 3) I do not hear the starter craking.

Is is the starter problem? or safety switch? Please advice.

Thanks

 

Sounds like you know enough to check the wiring to the starter. I was not sure of your level of expertise before.

You will need some help on this as you will need one person to turn the key while you check the voltage at the starter.

Just get a simple volt meter and ground the negative to the car body or the engine block and have your assistant turn the key to start. Then probe the terminals to see if any of them are getting current.

A wiring diagram for your car would help a lot. I do not have one, but if you can look at one it will tell you the color of the wire that sends voltage to the starter from the safety switch.

I like to work backwards on these things. See if you are getting starting voltage to your starter, if not track it back to the next component. This could be a starter relay or the safety switch; you would need a wiring diagram to tell you for sure.

I am afraid that the only way you will know if your starter is out is to remove it and have it tested.

Sam

 

Sam and All,

Thanks for all of yours help. I found the problem with the starter+ selinod. Bought the rebuild one and ask my mechanic to repplace it. The car starts every time now.

 

Wonderful!

I hope we were somewhat helpful. There are so many connections and electrical things that can go bad in the starter circut that it can be one of the toughest problems to run down. I am glad to hear that you car will soon be back on the road.

It is always nice when someone reports back, "PROBLEM SOLVED!"

Sam