Hello, I seem to be having a problem with fuse #18 blowing when I attempt to start my car ('97 SL320). This is the second time this happened. The first time the mechanic just changed the fuse and away I went. However, it happened again and we think it's got something to do with the starter. Any help to avoid mucho dollars on labor trying to find the problem? Thanks!

When the fuse blows does it interrupt the starter motor? According to my info fuse 18 provides power to the following items: cruise control switch, heated washer nozzles via the thermo-time switch, X30 connector block, DAS control unit and automatic dimming rear view mirror. As the diagram is drawn I do not see fuse 18 interfering with the starter motor control.

Hello, well my mechanic said he can't figure out what's going on because previously when he reinserted a new fuse in #18, the car started (I went out to the garage and the battery was charged but the engine wouldn't catch). He said we could either wait until the fuse blew again to determine the cause or search then. Naturally, I decided to wait and it took about three weeks before it happened again. It blew three times in my garage, once when I changed out the fuse myself, and twice when he was there testing the fuses (would you believe a house call for my car?) and I attempted to start the car. He then announced that since it blew when the car was starting, he believed that the issue was either with the starter or the ignition. However, now he can't seem to determine exactly why this is on-going and states thinks there may be a problem with one of the computers. He will look at it fresh in the morning to see if he can figure it out. This guy does imports all the time but maybe I should have brought it direct to Mercedes this time. He's a good guy and he's fair (who else comes to your house?) so I hesitate to stop doing business with him. Thanks for your input. I'll give him the description you provided tomorrow.

As such a fuse is a protective device. If the fuse is blowing when you start the car it is probably incidental to the starter motor. One of the items on that list above is drawing too much current. Each item has to be disconnected and the car must be started. When the item that is disconnected causes the car to not blow the fuse you have found the item that draws too much current...This might seem overly simplistic but having done this procedure many times I know it works.....

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The only thing I could suggest is to isolate the individual circuits connected to number 18 and see which circuit is causing the fuse to blow. The diagrams I have do not show the "Starter Lockout" relay being fused, there is a chance that it is powered up via fuse 18. This may explain why the fuse is blowing on start-up.