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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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2,704 Posts
Discussion Starter #1
I have reason to believe something is wrong with my auxiliary cooling fan relay.
I would like to check it out but have no idea where it is.
2621032

Is it one of the silver boxes in this picture? If so which one? They appear to be identical.
 

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The aux fan relay is in the separate fusebox with the black plastic lid. It's the black 40A relay provided it's not been changed. All the relays are listed on the fusebox diagram printed on the lid.
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
Joined
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2,704 Posts
Discussion Starter #3
Aha! Right I in front of the regular fuse box. Never noticed it there before. I guess I will start with jumping the pins to see if I can make it run. Thanks PN187!
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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2,704 Posts
Discussion Starter #4
Date code on it says 1989. So it is the original. Not sure how long they last.
 

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1989 190e 2.6
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224 Posts
Make sure your AC is fully charged. Mine was low and that was causing the aux fans not to run, all relays etc were fine.
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
Joined
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2,704 Posts
Discussion Starter #6
Thanks for that maranello, I will look into that too, though AC is working well ( it does have a tiny leak at the high pressure hose).
I have it rigged up so it will come on full at ~97C. It did that for a while and stopped. So I have two issues there.
Fortunately it is Winter and not needed at the moment.

I will report on the findings.
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
Joined
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2,704 Posts
Discussion Starter #7
So the AC pressure switch on the relay can disable the aux fans entirely?
I'll bridge the coolant temp sensor to see if that makes the aux fan come on at full speed next.
From the wiring diagram I see that the relay is a double throw in which both the hot side (with some switches/fuses/etc) and ground side (with some other switches/fuses/etc.) are relayed.

Anybody have a simple picture of where all these various switches/fuses/etc involved in this circuit are located under the hood?

I have not jumped the ground or hot side at the relay just yet to figure out if the issue is on the ground or hot side.
 
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