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  #1  
Old 06-13-2002, 08:54 PM
D Man
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Unhappy Auxillary fan always on

I'm a new member of the "diesel club" after purchasing my first MB about 3 weeks ago - an '83 300DT. I'm slowly going through the car and getting familiar with it. Upon cleaning the fuse box and replacing all the fuses I noticed the fuse for my auxillary fan was blown. Now, since I've replaced it, the auxillary fan runs all the time - as soon as the key reaches position 2. The only way to stop it is to remove the fuse or disconnect the connector just below the radiator. I tore-apart this same connector to make sure there wasn't internal corrosion causing a short. No shorts. Instead, I discovered the wires feeding the fan are always "hot" and providing power to the fan.
Can someone help point me towards a relay, thermostat, or other device that tells the fan to turn on? It seems something is stuck in the "on" position and is causing the fan to run continuously.

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Old 06-13-2002, 09:25 PM
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Find your A/C receiver drier. It's behind the passenger side headlight. It looks like a tube, it's that thing that people look into when they wanna find out if they still have freon in the system.

Once you found it.
There is a switch, or rather two pairs of connectors. One is on the receiver drier itself. That one in my car engages and disengages the compressor depending upon the freon pressure in the car.

The other pair is not a switch for me. It looks more like a pair of connectors. Just make sure that it's not jumpered to come on all the time.

I hope that makes sense.. good luck..
let me see if I can take a picture..
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Old 06-13-2002, 09:28 PM
MVK MVK is offline
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I think its the faulty auxillary fan thermo-sensor switch. when this switch is faulty it can do 2 things. Keep the fan on all the time or keep it off all the time. Also check the auxillary fan relay. Also there is a connection between receiver dryer temperature switch and auxillary fan.

It seems like someone had purposely jumped the switch to keep the fan running all the time as soon as you turn the key in. Some people do this to compensate their faulty cooling system. Not a good idea though.

MVK
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1985 300D Turbo 179,000miles
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Old 06-14-2002, 07:34 AM
D Man
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Thanks for the tips - I'll take a look. Can you tell me where the temperature switch and relay are located for the auxillary fan?
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Old 06-14-2002, 06:22 PM
MVK MVK is offline
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send me your e-mail address and I will send you the file with the location photo. Its about 1.2 mb pdf file.
MVK
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Old 06-14-2002, 07:34 PM
MVK MVK is offline
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send me your e-mail address and I will send you the file with the location photo. Its about 1.2 mb pdf file.
MVK
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Old 06-15-2002, 10:33 AM
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hello, my fan doesn't work now as well, and was wondering if you could send me the pdf file as well. thanks, adam 85 300d t
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Old 06-15-2002, 09:32 PM
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I too would like that pdf file if you can. Since putting a fuse into my "aux. fan" holder in the fuse box, my battery has died. I would like to know about other "relationships". Well, not concerning anyone on this list.. just the fuse/fan/thermo sensor etc.

thanks!
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1982 300D (266,001 mi.) looking and running great

Previously owned:
1976 450 SLC
1983 300D
1976 300D
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1982 Jaguar XJ6 (loved, but gone)
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Old 06-16-2002, 02:31 AM
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This might not be very helpful. However, I do not know where the 'switch' is for the freon pressure.



The blue 'switch' is the one that could be jumpered when the freon level is low to check the compressor. i.e, if you jumper the cables then the compressor will engage even if the freon level is low.

The two wires at the top (white connectors in zip tie) could be jumpered to make the aux. fan run.

hope that helps... I'm not even sure if mine is still correct.. but it works fine so I'm not gonna do anything about it.
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Old 06-16-2002, 10:17 AM
MVK MVK is offline
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Well all those who want that pdf file, please post your e-mail address. I cant send you anything without it. Also tell me the exact model of car.
MVK
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Old 06-16-2002, 10:55 AM
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hello, my e-mail is adambush@devil-dog.com for an '85 300d t california model - thanks so much!!!
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  #12  
Old 06-16-2002, 12:11 PM
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Thanks MVK. My email address is in my profile, but here it is again:

nellotare1@juno.com

It's the '82 300D that's in my signature.

and thanks for the file! I have an appointment tomorrow with indie tech and want to mention these things to him regarding my problem.. which seems to be a combination of things since getting my AC going on Monday.

and thanks Holson Adi for the pic about the switches also! Mine seem to be in order but who knows?

Thanks again everyone.
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Nello Tare

1982 300D (266,001 mi.) looking and running great

Previously owned:
1976 450 SLC
1983 300D
1976 300D
also
1982 Jaguar XJ6 (loved, but gone)
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  #13  
Old 06-16-2002, 12:22 PM
MVK MVK is offline
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Thanks for the e-mail addresses guys. Now just bear with me for 2 more days because I am in Manchester, NH this weekend. and will be back to home in Ny on Tuesday. Thats when I will send you folks the pdf file. I thought I had in my yahoo briefcase but could not find it in there so I will have to wait till I get home.
MVK
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1985 300D Turbo 179,000miles
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  #14  
Old 06-16-2002, 09:28 PM
MVK MVK is offline
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Check the location of various relays on the 1985 300D

turbo

[url]http://www.************************

Then look for your car and model, then look under elecrical, look for relays, look for temperature switch,this will give you a picture of all relay location. Look for 5 in the picture. thats the aux fan relay.
Hope this works
MVK
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Last edited by MVK; 06-17-2002 at 08:32 PM.
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  #15  
Old 06-18-2002, 01:11 AM
MVK MVK is offline
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Aux Fan relay Photo

hope this helps. This relay is also claaed ice cube relay as it looks about the same size of an ice cube. Its located, at least in my 85 300D turbo, under a black box, on the right side( facing car) above the wheel, by the blue valve, in the engine compartment.

MVK
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Auxillary fan always on-aux-fan-relay-copy.jpg  

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