Join Date: May 2012
Vehicle: 2004 SLK 320
Other Toys: 2011 Mercedes E350
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High Beam Relay is internal to headlight switch
Here's an update. Got the relay from Autohauz, plugged it in and voila - oops - I mean bummer. Still no high beams. Talked to my mechanic and he looked it up for me on his pay-for mechanics web service. He cross referenced the wiring diagram to parts and it appears the high beam relay is internal to the light switch. The light switch is basically a multi-function set of relays and includes the fuse box that is inside the dash. I did a quick surf and we are talking $350 for this part (A 170 545 03 04). My mechanic warned me this would cost a lot! Yikes!
Things get even curiouser... I used EPC to get the switch part #. In the diagram they also show a "fuse". This is distinguished from the "fuse links" which are what we (I) typcially think of. You know - the 7.5a brown and 15a blue fuses. EPC names these "fuse links". The fuse is part# A 003 994 16 45. I did a web search on that and only found 2 U.S. sites that had it. Both listed it as a "lock". go figue...Wait a second, as I am typing this and looking at the EPC diagram, it probably is a lock and the EPC description is incorrect! The part and location on the diagram looks like the locking plate for the screw that secures the fuse box / lamp switch to the dashboard frame. You can see both the screw and lock plate when you removed the access panel and look at the bottom right of your fuse box. Another quality problem with the EPC site!
Next step is still more diagnosis - will likely run some continuity tests to see where power is being lost. I think I'll start with the blinker / headlight switch on the steering column. At least thats a cheaper part (A 170 540 03 44) - $100 on e-bay, somewhere around $200 on auto parts suply web sites.