1987 560sl # 12 fuse keeps blowing

[dialric]

Got in the sl last night, i saw the clock was not working, went for a ride and found out the radio was out also. got home and found # 12 fuse was blown.. i tried a couple more fuses, same thing happened instantly. Everything was working fine for along time. Car was driven and has not been in storage. I decided I would try to fix it myself with your help. I could not find anything about my problem on this site. I really dont know where to begin but I need a diagram of the circuit for fuse # 12 And as much input I can get to correct my problem from all you Sl pros. thank Richard

[coleyjf]

Hi there

I've a UK handbook and according to it (UK 1988 owners manual) fuse #12 is for:

• Diagnostic
• Clock
• Trunk Light
• Roof Light
• Entrance Light
• Hazard Warning system
• Auto antenna
• Radio
• Trailer turn signal control.

The US model can't be too different I should think.

My 1st guess would be the trunk light switch ( had you put something big in the trunk?) this is on the right hand side of the trunk near the hinge.

2nd guess would be a bulb gone short-circuit - unfortunately quite a few to choose from - BUT were the doors open when you replaced the fuse (this could discount the entry lights)

3rd would be the auto antenna.

A simple test would be to remove the fuse and connect a basic meter across the "output" side of the fuse (not the "live side) and a decent ground/earth (nearly any of the chrome or stainless bits). You should read a short circuit or very low resistance. THEN try taking out the bulbs one by one and/or operating the door light switches and the interior switch and Switch the radio OFF.

If it's the actual radio circuit or the clock or the diagnostics ( unlikely I would think) it gets a bit harder!

Hope this helps

Cheers

Jim

[meltedpanda]

common place for short is in hinge at trunk, or wire off a bulb connection , shorting to ground - good luck

[dialric]

Ok heres what i did unpluged antenna --- took out the trunk light bulb --- pulled out the trunk light switch and bulb --- and cut the 3rd brake light wires --- checked each entrance light and removed bulbs --- I checked the ouput side of fuse position 12 with the meter on ohms red lead on the ouput of the fuse and blazck lead from meter to a good ground. NOTHING SEEMED TO CHANGE Can i do this with a test light or do i have to keep using placing new fuses. What is my next step. thanks for the help.

[dialric]

Does anybody ave a diagram of the fuse 12 curcuit ?

[donbryce]

My CD for the 1987 560SL shows fuse 12 is also for the anti-theft alarm and 'warning system', in addition to the antenna, clock, courtesy lamps, trunk lamp, radio, and turn signal/hazard lamps. I couldn't find any single wiring diagram for 'fuse 12', but rather, diagrams covering each of the above, way too much to post here. It did indicate all are on 'circuit 30', so perhaps an electronics guru could help you. Meantime, check the alarm system, a likely culprit. There are switches wired onto the door locks and the trunk lock. On my '86, the door switches were in real bad shape, partly from someone trying to eliminate the alarm system, partly from corrosion.

[dialric]

Can u tell me how to check the alarm system? Is there a main plug that I could unplug?

[MAGV5]

Richard,

Any further useful advice is going to require a multimeter. Do you have a multimeter and do you know how to use one (measure volts & resistance)?

MAGV5

[dialric]

Yup, have a meter and fixed my problem. Did it with a test light. Problem was the red wire leading to the visor lamps. thanks for the help everybody.