I've looked through the diagrams, but I'm just not familiar enough (yet) with the electrics of this car to know what to look for. Some previous owner has done some dinking around with the wiring on this car and I'd like to undo all they've done and set it back to the way it's supposed to be. This relay has a wire connected to it that was then connected to another wire that I've yet to find the end termination of. Figuring out what this relay is for would help me know where to look. The car is a 1987 190D Turbo. The relay is located just south of the fusebox and was under a plastic black cover. You can see the yellow/green wire he stuffed into one of the pin holes for the relay in the picture.

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2010 Mercedes E350 4Matic - 77k miles
1986.5 Nissan D21 V6 4x4 - 276k miles
1987 Mercedes 190D 2.5 Turbo - 3??k miles
1983 Mercedes 300SD turbo parts car
2017 Honda CBR500R - 15k miles
2016 Suzuki GSX S1000 - 9k miles

Manual switch for AC compressor or aux fan? This picture suggest aux fan.



Sixto
98 E320s sedan and wagon

Should have mentioned that before, I've found 2 additional switches at the moment, one of which goes to the AC compressor, the other turns on the blower fan for the AC/heat. It's weird though, if I push the defrost button, the blower comes on and can be adjusted normally via the OEM 3-position switch. None of the other climate control buttons appear to do anything.

Don't know if this particular relay/etc. is involved in that somehow or not. I haven't been able to find it in the wiring diagrams.

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2010 Mercedes E350 4Matic - 77k miles
1986.5 Nissan D21 V6 4x4 - 276k miles
1987 Mercedes 190D 2.5 Turbo - 3??k miles
1983 Mercedes 300SD turbo parts car
2017 Honda CBR500R - 15k miles
2016 Suzuki GSX S1000 - 9k miles

Oh awesome, yeah that definitely looks like it! So, the aux fan is one of the electric fans on the front of the car, correct? Not the AC/heat blower motor?

__________________
2010 Mercedes E350 4Matic - 77k miles
1986.5 Nissan D21 V6 4x4 - 276k miles
1987 Mercedes 190D 2.5 Turbo - 3??k miles
1983 Mercedes 300SD turbo parts car
2017 Honda CBR500R - 15k miles
2016 Suzuki GSX S1000 - 9k miles

Yes, they're on the very front.

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

This is what that area SHOULD look like. There are two relays...the yellow one controls the power seats, the orange controls the high speed function of the radiator fan (low speed has a separate relay in the fuse box). The blue fuses are for the seats, the red are for the alarm system.

The stock relays at this location are black, but they are NOT the ususal ice cube relays. They are internally fused. They are also a fire hazzard, and should be replaced with the more modern externally fused relays in my photo.

Bypassing the fan relay with an unfused switch appears to be the plan in your photo This is ULTRA DANGEROUS, as the high speed function is fed directly from the battery + post with NO FUSES.

Attached Thumbnails

 

I assumed whatever wiring this previous owner had done would probably be horribly unsafe. Looks like my assumption was correct. I plan to tear all the wiring he did out and set things back the way they are supposed to be. Thanks for the help guys.

__________________
2010 Mercedes E350 4Matic - 77k miles
1986.5 Nissan D21 V6 4x4 - 276k miles
1987 Mercedes 190D 2.5 Turbo - 3??k miles
1983 Mercedes 300SD turbo parts car
2017 Honda CBR500R - 15k miles
2016 Suzuki GSX S1000 - 9k miles