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1996 E300D
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Discussion Starter #1
Ok after a slew of troubleshooting and indie speculation I finally think I figured out my AC woes. So now I think Della might be running hot but I am not sure as to what the normal operating temp range should be for diesels...

Here is a run down of recent events to give a better perspective. An indie told me my aux fans were not working. He told me it could be the module or the motor or both. So I did some testing on my own and deemed the aux motor to be dead. So in light of spending $225 on a new motor and god knows how much on a possible new control module I opted to put in my own electric fans.

I bought them off Summit and they are the same size as the OEM fans and deliver 1500cfm together to keep it cool. They fit perfectly. I have to assume that these fans do a better job than the OEM fans b/c these are designed to cool small block V-8's. They are running on a dedicated, switched circuit, then to two seperate 20a fuses then to battery. They run great and the AC works good too now.

The only issue is that now that is it getting hotter outside I am worried Della is running too hot. The aux fans and delivering a great amount of air yet the temperture doesn't seem to drop when they are on. I have a OBD-II datalogger and the readings I am getting are what seems to be the normal operating temp to be around 198-200F. However sitting in traffic with it at 85 degrees this afternoon, AC on high, it was as high as 226F. That seems too hot but I could be wrong.

It has enough coolant in it and the aux fans run in the "pushing" direction. I still think it is too hot, any guidance? I think there might be a possibility the radiator and condensor fins need declogging with some possible degreaser and low pressure water?
 

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1996 210.020
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You should inspect and if necessary, clean the radiator and condenser airways. It's hard to see debris that gets lodged deep in there, but you can try putting a work lamp in the shroud for the mechanical fan and looking through the front. Removing the auxiliary fan will help.

However...

I would not assume that the aftermarket fans work as well. The OEM unit is powerful and well shrouded to cover a lot of area.

You didn't ask, but I'll answer one question. It is not a good idea to replace your factory auxiliary fan assembly with anything else. If you forget to turn it on and need it, you could damage your engine, air conditioning system, or both. In addition, if you hook an aftermarket assembly to the factory controller, it may be unreliable.

Edited to add: also check your mechanical fan clutch. You might need a new one.
 

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1996 E300D
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Discussion Starter #3
Matt thanks for the concern. I have a switch running in the interior, me being borderline OCD I switch it everytime.

I guess everytime I saw the OEM fan run it never appeared to be turning nowhere near enough to deliver that kind of CFM. I have no concrete evidence though to back that up...:)

I guess I was just looking to see opinions on wheter 226F was too hot or not. It looked a little cruddy under there when i was putting them in. I believe removing the condsenor will get it cleaned the best but don't want to discharge the R134... I am going to take the degunking approach but was looking to see if there were more items to check...

Matt, how can I tell if the clutch needs replacing, the fan seems to spin easily...
 

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107C is pretty hot, but the red line is around 120. I certainly would not be comfortable with 107.

As for the factory auxiliary fan, it is infinitely variable. If you saw it on a low speed, of course it will not be moving a lot of air. But when the engine temperature or the refrigerant pressure or temperature rises, the fan speeds up. It produces a very loud howl if running on full speed. Definitely louder than any aftermarket fan that I have used (and I've used a bunch of them on various cars).

One not-very-good way to test the fan is to see that it resists turning just after shutting down a hot engine. It should also come to a stop very quickly when the hot engine is stopping.

And don't discharge your refrigerant. Take it to a shop to have it reclaimed. It won't cost you a lot, but it is illegal to vent refrigerant. The consequences if you get caught are quite severe.
 

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Discussion Starter #5
It was only at 226F for a very short period of time, once I got out of gridlock it cooled back down to 200F pretty quickly. One thing I did notice is that the AC doesn't make a difference in temp so maybe the lower regions are clogged with grime creating a diminished cooling ability. I am going to hit the fins with simple green and a water hose this weekend and see what happens.

Since the engine driven fan is not controlled by a module, why not take it out and put a big 14-16inch electric fan in? Surely a big fan like that can provide way more cfm that the OEM mechanical fan. My only concern at that point is that I would then have 3 electric fans drawing 12amps each and might create an overload on the alternator.

Thx for the tip on the R134 but I would never discharge anything like that into the air. The only way I would take off the condensor is to replace it b/c the next possible AC solution for me is to replace the condensor. Every other part has checked out ok on a dye test, someone here mentioned to me (might have been you) there might be a microscopic leak in the condensor that is making the r134 leak.

IYO If I did nothing and let it run up to that range of 226F on occasion, will it create any long term performance issues with the engine itself? Good to talk to you again Matt.

Chris
 

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Discussion Starter #6
Matt,

Another quick question, do you know if the OEM aux fans push or pull air? There is a possibility I have mine set to turn the wrong way as well...
 

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They push air from the front toward the condenser. They turn clockwise from the front (same as the engine).

If they were turning the wrong way, they would not only not help, but actively hurt the cooling when you are moving.
 

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It was only at 226F for a very short period of time, once I got out of gridlock it cooled back down to 200F pretty quickly. One thing I did notice is that the AC doesn't make a difference in temp so maybe the lower regions are clogged with grime creating a diminished cooling ability. I am going to hit the fins with simple green and a water hose this weekend and see what happens.

Since the engine driven fan is not controlled by a module, why not take it out and put a big 14-16inch electric fan in? Surely a big fan like that can provide way more cfm that the OEM mechanical fan. My only concern at that point is that I would then have 3 electric fans drawing 12amps each and might create an overload on the alternator.

Thx for the tip on the R134 but I would never discharge anything like that into the air. The only way I would take off the condensor is to replace it b/c the next possible AC solution for me is to replace the condensor. Every other part has checked out ok on a dye test, someone here mentioned to me (might have been you) there might be a microscopic leak in the condensor that is making the r134 leak.

IYO If I did nothing and let it run up to that range of 226F on occasion, will it create any long term performance issues with the engine itself? Good to talk to you again Matt.

Chris
You're OK as long as you keep it out of the red. But when things are marginal is when you get to the red, so be careful.

As for replacing the mechanical fan with electric, you are seriously underestimating the power of that fan. You can easily remove several horsepower (or Kw) from the belt without issue. One horsepower (~750W) at 12 volts is over 60 amps! The mechanical fan and clutch (like the auxiliary fan assembly) is an integral part of your system and needs to function as intended.

Another thing to consider is a dirty radiator on the inside. If you see scale on the plastic parts where you can see (after removing a hose), you almost certainly have some in the tubes. But clean the air path first.
 
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