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  #1  
Old 05-29-2012, 03:53 PM
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'91 300CE - Auxiliary fan fuse blown (16A to 25A)

I noticed my car running hot in 90F weather - at idle, operating temps above 100C with A/C running. Auxiliary fans are only kicking on at high speed and when engine temps are 105-110C - as it's supposed to - and this brings the temps down quickly.

But, I had no LOW speed aux fan, which is supposed to run when the A/C is on and when the appropriate pressures are reached. I checked the fuses and noticed Fuse D (Red 16A) was blown. I read some old posts from Arthur Dalton about replacing this fuse with a 25A one - per Mercedes - when they put dual Aux fans in the car. Mine does have the 2 fans, so I replaced the fuse with a 25A and so far so good. Fans came on at low speeds and kept operating temps around 85C. Turned off the A/C and the fans ran for another 5 minutes, maybe, and then shut off.

But, I am worried... (I have PM'd AD, and hopefully he will respond, but I haven't been on the board in a while myself).

What do you guys think? Anything I can check? I probably need to check the amperage draw of the fans, but I'm not sure how to do that...?

Thanks, ryan
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  #2  
Old 05-29-2012, 04:14 PM
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Have you check the ballast resistor?
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  #3  
Old 05-29-2012, 04:17 PM
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No, and I meant to ask how to do this as well. Not exactly sure as to the procedure...
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1984 300D
1972 250
1986 560SL
1991 300CE
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Old 05-30-2012, 05:36 PM
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Quote:
Originally Posted by rgnprof View Post
I checked the fuses and noticed Fuse D (Red 16A) was blown. I read some old posts from Arthur Dalton about replacing this fuse with a 25A one - per Mercedes - when they put dual Aux fans in the car. Mine does have the 2 fans, so I replaced the fuse with a 25A and so far so good. Fans came on at low speeds and kept operating temps around 85C. Turned off the A/C and the fans ran for another 5 minutes, maybe, and then shut off.

What's the benefit of swapping the red 16A fuse with the blue 25A fuse for Fuse D?
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Old 05-30-2012, 05:46 PM
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Don't know if there is any advantage - that's what I've been trying to figure out. Arthur Dalton posted several years ago about switching out the 16A for a 25A because Mercedes had upgraded to a dual fan system - which my car has. Arthur has since informed me that my set-up was NOT the one he was referring to in his old post.

So, I went back to a 16A fuse in fuse D and have been driving the car all day in 90F heat with no blown fuse. Fans are running as they are supposed to and car is definitely running cooler - generally under 100C. It still runs hot - usually between 90C and 100C, but better. Never gets much above the 100C mark now and it has not reached the 105-110C mark where the high speed aux fans kick in.

ryan
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1984 300D
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1986 560SL
1991 300CE
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