Hi,

it looks like my aux fan is intermittant. can someone tell me when it should be on? should it come on with the AC?

also, which is the aux fan relay? where is the fan plug, i followed it and its like it is wired in solid. I dont want to cut it to test for voltage if I dont have to. the relay fuse and the fan fuses are good..

thanx

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1982 300CD Turbo (Otis, "ups & downs") parts for sale
2003 TJ with Hemi (to go anywhere, quickly) sold
2001 Excursion Powerstroke (to go dependably)
1970 Mustang 428SCJ (to go fast)
1962 Corvette LS1 (to go in style)
2001 Schwinn Grape Krate 10spd (if all else fails)

The fan is thermostatically controlled! If it cycles on and off while the engine is running, then it is doing it's job! If you are experienceing something else or5 mean something else by intermittent, please elaborate?

On my 123's The relay is located on the driver side fender well under a black plastic cover...should be two little ice cube relays....If they have the same number of pins you can swap them for a test....Most of the Aux fan problems are worn out brushes and shaft bearings that have gone dry....

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1978 Yellow 300D (The Mustard Toad)
1980 Blue 240D (The Iron Toad)
1989 Grey Mitsu.4WD Mighty Max Pickup (Needs a Diesel transplant bad)

(Open the pod bay doors HAL)

sorry, intermittant for me means last time I had the hood up with the engine at 100c it was running. now it is not...

__________________

1982 300CD Turbo (Otis, "ups & downs") parts for sale
2003 TJ with Hemi (to go anywhere, quickly) sold
2001 Excursion Powerstroke (to go dependably)
1970 Mustang 428SCJ (to go fast)
1962 Corvette LS1 (to go in style)
2001 Schwinn Grape Krate 10spd (if all else fails)

I will flip the relays. the one in front is hot and the one in back is cold. do you know which one controls the fan?

__________________

1982 300CD Turbo (Otis, "ups & downs") parts for sale
2003 TJ with Hemi (to go anywhere, quickly) sold
2001 Excursion Powerstroke (to go dependably)
1970 Mustang 428SCJ (to go fast)
1962 Corvette LS1 (to go in style)
2001 Schwinn Grape Krate 10spd (if all else fails)

You can trace the wire from the realay to the fan...I cannot remember but it is an easy trace.....If the hot relay is the fan....that most likely says fan motor problems...It is possible to rebuild your fan motor without too much trouble...

__________________
1978 Yellow 300D (The Mustard Toad)
1980 Blue 240D (The Iron Toad)
1989 Grey Mitsu.4WD Mighty Max Pickup (Needs a Diesel transplant bad)

(Open the pod bay doors HAL)

any writeups you know of for the aux fan? I can feel a indexing when I turn it like it is energized but not running. I tried to trace the wire but it joins into the large bundle on the driver side and I didnt want to cut the bundle apart. Is there a plug on the fan somewhere when I pull it off so I dont have to cut the wire?

__________________

1982 300CD Turbo (Otis, "ups & downs") parts for sale
2003 TJ with Hemi (to go anywhere, quickly) sold
2001 Excursion Powerstroke (to go dependably)
1970 Mustang 428SCJ (to go fast)
1962 Corvette LS1 (to go in style)
2001 Schwinn Grape Krate 10spd (if all else fails)

OOps!...My mistake I was thinking of another wire....Yours does go into the bundle...
Yes...There is a connector you can unhook about a foot and a half along the wire leaving the fan cage.....Just unhook the connector...only a two conductor cable...You can hook 12 volts + & - to the cable either way...the fan will run both directions as a test....

__________________
1978 Yellow 300D (The Mustard Toad)
1980 Blue 240D (The Iron Toad)
1989 Grey Mitsu.4WD Mighty Max Pickup (Needs a Diesel transplant bad)

(Open the pod bay doors HAL)

found a rebuild post. I will try this if the 12v test shows what I am sure it will show.......


Bosch Aux Fan - New Bearing/Rebuilt - 123 Body

__________________

1982 300CD Turbo (Otis, "ups & downs") parts for sale
2003 TJ with Hemi (to go anywhere, quickly) sold
2001 Excursion Powerstroke (to go dependably)
1970 Mustang 428SCJ (to go fast)
1962 Corvette LS1 (to go in style)
2001 Schwinn Grape Krate 10spd (if all else fails)

I rebuilt both of mine....and a Volvo 740 the same way...they run great now.....If you have trouble finding the brushes just get some larger ones at a starter shop and file to size...The graphite files easily.....

__________________
1978 Yellow 300D (The Mustard Toad)
1980 Blue 240D (The Iron Toad)
1989 Grey Mitsu.4WD Mighty Max Pickup (Needs a Diesel transplant bad)

(Open the pod bay doors HAL)

The aux fan on the subject model vehicle has nothing whatsoever to do with the engine. It is actuated by a temp switch on the a/c receiver/drier and nothing else. It will only come on if the refrigerant temp gets hot enough (62 degrees C) to close the switch. (If you refrigerant level is a bit low, it might never get hot enough, even with the a/c operating.)

With the key in "Run," jumpering the temp switch on the receiver/drier should actuate the fan relay and power the fan. The relay is powered through fuse 12; the fan through fuse C.

Coolant temp is not a factor in the operation of the aux fan.

where were you an hour ago.... . .. the fan works fine. Now I have to drill and tap one of the bolts that broke off when I was removing the fan.... so the aucx fan is not part of the normal cooling system? I was hoping this was the reason I run at 100C all the time? I have a thermostat on the way but I most likely will not get it until thursday. I am definitely learning a lot about German engineering...

__________________

1982 300CD Turbo (Otis, "ups & downs") parts for sale
2003 TJ with Hemi (to go anywhere, quickly) sold
2001 Excursion Powerstroke (to go dependably)
1970 Mustang 428SCJ (to go fast)
1962 Corvette LS1 (to go in style)
2001 Schwinn Grape Krate 10spd (if all else fails)

Working on my car, of course!!!!

I think it's fair to say that it is an air conditioning component.

My Benz is a 300D 1983. If yours is anything like mine, the fan is most directly connected to the Air Conditioning system. When your AC is on, the fan runs all the time. 100C sounds like it's a little hot to me though! Your thermoswitch will be on top of the AC receiver/dryer. there are 2 sets of wires, one for the compressor....making sure there is refrigerant pressurised in the system. Those are connected to a small silver looking can on the rectangular part on the top of the receiver dryer. the thermoswitch is located on the same rectangle, but off to one side of it. Jumping those two wires together will cause your fan to run all the time. If it still operates intermittently, then you have problems with the fan motor and it could need to be replaced or rebuilt.