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#1
10-27-2009, 12:37 AM
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1987 420sel #5 fuse keeps blowing out
I have a 1987 420sel with a 151,000 miles on it. During the summer the #5 fuse began blowing every other day for a week then stopped. As of last week the #5 fuse began blowing again. When I replace the #5 fuse it sometimes is good for a day and sometimes it blows out again the same day I change it.
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#2
10-27-2009, 01:10 AM
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I dont have my owners book with me... what all does that fuse control?
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#3
10-27-2009, 01:21 AM
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OK, today my #5 goes too. First time. Just replaced it seconds ago, after finding a post on dead cluster instruments.
It controls the instrument cluster, for one thing, that's how I noticed. I have another recent electrical issue, which may be related. I get the fast-blinker rate on the right side, intermittently, even within the same turn it jumps from slow to fast to slow... Of course I get the blown bulb indicator coming on and staying on. I check the blinkers and they both light. I haven't done the corrosion rub-down on everything yet.. But maybe my #5 was just fed up with too much signaling? Because I see #5 and #6 are involved in signals. I haven't broken out the electric manual yet... we'll see how she reacts in the a.m. If it blows again... I'll blow the dust off that manual.
__________________
Cheers! Scott McPhee 1987 300D
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#5
10-29-2009, 08:04 AM
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Fuse #5 also supplies power to the air-injection clutch on cold/cool mornings.
Try removing the RELAY at position "E" in the fuse box & see if the fuse quits blowing.
__________________
MERCEDES Benz Master Guild Technician (6 TIMES) ASE Master Technician Mercedes Benz Star Technician (2 times) 44 years foreign automotive repair 27 Years M.B. Shop foreman (dealer) MB technical information Specialist (15 years) 190E 2.3 16V ITS SCCA race car (sold) 1986 190E 2.3 16V 2.5 (sold) Retired Moderator
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#7
10-30-2009, 02:34 PM
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No, that means the air injection pump chutch is drawing too much current.
Leaving the relay out depends on how GREEN you are.
__________________
MERCEDES Benz Master Guild Technician (6 TIMES) ASE Master Technician Mercedes Benz Star Technician (2 times) 44 years foreign automotive repair 27 Years M.B. Shop foreman (dealer) MB technical information Specialist (15 years) 190E 2.3 16V ITS SCCA race car (sold) 1986 190E 2.3 16V 2.5 (sold) Retired Moderator
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#8
10-30-2009, 02:52 PM
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Quote:
FYI, fuse number 5 powers: LT monitoring unit A/C comp ctrl relay push button control unit switchover valve group aspirator blower aux water pump air injection relay gear select sw The relay M.B.DOC is talking about controls the air injection pump & switchover valve solenoid; one of those is probably bad. It's mainly an emissions item, but could affect driveability. Air pumps aren't required everywhere, so you might be OK without it.
__________________
A.S.E Tech A1,A6,A7,A8 & MVAC 609 + EPA 608 Unless stated otherwise, any question I ask is about my greymarket 1985 380SEL. 
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#9
10-31-2009, 05:38 AM
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Where are the air injection pump & switchover valve located. Also at times when I am accellarating there's a noise that sounds like a clicking fan that comes from under neath the car. Could the injection pump or switchover valve have anything do with this. My mechic said the noise is caused by my engine lifters. Is this a hard fix.
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