Could some of the wires in the Auxiliary fan Circuit be crossed?If you're getting
High fan with a Cold engine...It sounds like maybe the wiring from one of the two relays is crossed
[successfully,Meaning No Sparks But also not correct],
OR your surmise about the engine temp sensor being bad could be it.
OR somehow the wiring connector for the engine temp sensor has become disconnected in the Melee.

BUT with as many little fingers that will have been in that pie,once you get
it back...I would locate and trace out all the wiring and connections to make sure.

Here's the scoop on fan ReMoval:

Chris W. Chris W. is offline
Registered User

Join Date: Jul 2001
Posts: 208
Let's change the Aux Fans on a W124!
It’s true. Yes Virginia, you can change the aux fans in a W124 E Class without pulling the radiator or the bumper, or even the headlights. At least this is true for the dual fan version. I had researched it on the site, but there seemed to be a variety of opinions.

My car is a ’95 E300D. There are a couple of tricks I learned this weekend. Here are the basic steps. This all goes easier if the car is lifted in the front somewhat, so you can work on it from underneath when needed (which is not often), and also just not have to bend down so far. I did most work while sitting on my $29 Sam’s Club office chair with adjustable height, in front of the car.

Remove the horns. They are bolted to an odd shaped brace which is located in front of the aux fan shroud. One nut and you’re done there. You’re going to have to remove that brace, too. Now look at the top of the radiator. There are two big spring clips, one on each side, holding the radiator to the front structure of the car. Lever the clips up and off, and this will allow you to tilt the radiator back towards the engine. You need to do this to gain access to the top bolt for the brace, which you reach from the engine side. It’s invisible until you tilt the rad out of the way. I used a ¼” drive ratchet and socket.

The bottom bolt for this brace is best done with a wrench from above or below. It’s centrally located and a bit hard to see, but not hard to remove. Hardest thing is starting the bolt again when you are re-assembling. There is a third bolt which is obvious, which also holds down a bracket for the trans cooler pipe loop running in front of the aux fans. Undo that one and now you’re done with the brace and you can remove it.

Now undo the bottom bolt on the trans cooler line so you can be able to move that line up and out towards the front of the car when you’re dealing with the aux fan shroud. Don’t bend that line excessively, but it will be able to move as you need it to.

The aux fan shroud is the biggest PITA of this whole operation. It’s held in by six plastic rivets. From another post about this subject, the MB part number is 123 990 0092. I was able to lever out/off the top four rivets using two small screwdrivers, one on each side, and get them out intact. The bottom two are real PITAs. I just went ahead and destroyed them using a large screwdriver from underneath, levering on them until they broke and came out. The bottom of the aux fan shroud is just held in with tabs into slots, so no more fasteners.

At this point you can start to work the aux fan shroud up and out. It is all just thin plastic and quite flexible. It takes a lot of bending, moving, and grunting and groaning to get it out, but it will come out. Mine cracked slightly in one place, but no biggie at all. It doesn’t seem like it will work around the bells of the fan motors, but it will. Just work at it.

At this point, it’s handy to have a shop vac. If your car is like mine, about 2 pounds of bugs and leaves and grass and flora and fauna will either fall out or need to be vacuumed from the bottom of the A/C condenser. I’d bet that a good 10% of the condenser (and consequently the radiator) air flow was blocked by all the crap in there! I took a toothbrush, an air blow gun, and also my shop vac, and worked all the crap out of the fins. Just doing this alone has gotta help cooling efficiency a good bit.

Now you can see the actual fans. The two are held together on a surrounding figure-8 (or “infinity figure”) shaped frame which is bolted to the A/C condenser itself. There are two 8 mm bolts on each side, all slightly different, and two in the center. On the driver’s side you can easily undo the two bolts which are running fore and aft, which are actually attached to a small bracket which stays on the aux fan frame. Don’t undo the two other bolts on the driver’s side which run side to side – no need, yet. You can undo the center two bolts easily also. Very obvious. Now on the passenger side are two PITA bolts, running side to side. The top one has a nut, and the bottom one is threaded into the fan frame. You just have to work those two carefully, using a thin 8 mm wrench. It is VERY handy to have a ratcheting box end wrench for the bottom of the two bolts. There is not much room to work as the headlight frame is close by, but you can do it.

Once you get all six bolts out, you’re golden. Work the fans up and out and you can disconnect the wiring harness. You can disconnect each fan independently and leave the main harness in the car.

Assembly is the reverse of removal as they say. Getting the bottom passenger side 8 mm bolt started on the fan frame is another PITA but it can be done. IMHO you don’t even need this bolt as the other 5 are plenty.

And getting the plastic shroud back in is another PITA, but it can be done. Don’t forget to put the radiator back forward and put the two clips back on, or else you’ll chew up the rad with the mechanical fan, which you don’t want!

Hope this helps someone out there. I think all the W124’s are reaching the age where all these fans seem to be failing.

Rgds,
Chris W.
'95 E300D
Reply With Quote

AND:

That is correct .. You have it down. They are two different circuits, but they both share the same fan motor..
And the resistor circuit is ac pressure controlled, with the resistor dropping the voltage , resulting in LOW fan..whereas the engine coolant temp circuit by-passes the resistor, giving full 12v to the same fan motor, resulting in HIGH fan.
Two easy DIY test to verify these fan circuits is :
For Low fan, jumper the pigtail pressure sw at the ac drier.
. that test verifies low fan fuse, relay, resistor , and connecting wires.
For HIGH fan circuit, you simply remove the connector at the engine coolant temp sw/thermistor..that defaults the CC unit and results in HIGH fan. That test the high fan relay, fuse.wiring and CC unit..it does not test the resistor b/c the R is not in the high fan circuit.

These are very simple, fast tricks of the trade for circuit verification and are done whenever one suspects fan problems.

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'84 300SD sold
124.128

Thank you for the detailed removal of the fans, saved me for a lot of searching thru the forum.

Mine was a new assembly as well, and also cost just over $200. It was not OEM, and it was clearly not up to the job. Never again.

thank's for the heads up Matt L . I'll go the repair way first, if not I am off to the salvage yard.

Finally found the fans at a friends shop. Tools that you need are a 8 mm, 10 mm and 12 mm ratchet and a small long pair of pliers to reach and take out the 2 middle screws. I was surprised how easy they are to replace, no need to remove the bumper or the radiator. After taking the horns of and removing the radiator and condenser clamps I was able to push the radiator back enough the reach the bolt that holds the crossbar on which the horns are mounted. After removing the cross bar I removed the side screws that hold the fans to the radiator ( 2 on each side) and the tricky one were the 2 screws in the middle between the fans under the protective shroud. There is a easier way but you would need to remove the 4 plastic clamps that hold the protective shroud on the condenser but they are plastic and really old so you better have new ones if you plan on taking them off, this would easily make the 2 middle screws reachable but since I did not have 4 new plastic push clamps I wiggled a thin 8mm wrench in there and after a good 5 minutes at each screw I was able to take them off. After removing all 6 screws and unplugging the power connection the fans together with the shroud are easily sliding out. Once you have them out you can easily remove the protective shroud by pushing the 4 protective clamps from the back , and this will leave the fans free. Make sure to clean the condenser , the shroud will be full on the lower side with leaves and bugs. After replacing the fans and connecting everything back(use some contact cleaner in the power plugs), put the 6 screws back ( one thing I noticed the side screws that hold the fans to the condenser, one on each side has a nut and the other one has no nut, it has threads directly in the condenser piece, so be careful when you remove them so you will not lose the nut). Last thing that you need to install is the protective shroud, easily slide it in and check that it grips in the lower side of the condenser and put the 4 plastic push clamps back and you are done. Now test and off you go.

Another thing I don't remember that I wrote about is that I found my power drainage problem, it was the power antenna, after disconnecting it problem was solved. Now I just wait for the summer so I can take the hole antenna out and repair it, it works fine except of the power drain it causes. Thank you for all your help.

Glad you got it working. I got my fans used. They're still running after 9 months. I was amazed at the bugs that get collected back there.

(Its sounds like the clutch on the antenna isn't working to shut down the motor.)

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92 300D 2.5L OM602 OBK #59