e series cooling mod - calling JimF & Arthur D.
 

i have read your animated discussions on the cooling mod for the v8's including the ones with italianbenz. it appears that the v8 mod is accepted and valid, however there is some point of contention as to applicability to the 6 cylinder / E series platform. Jim and Arthur, I think your discussions proceeded on the premise that on the E series you would be looking at the low speed aux fan switch on the A/C drier. i believe that this switch is purely pressure activated and is not applicable. my thinking is that maybe you should look at the sensor on the thermostat housing which appears to be very similar to the one that Jim refers to as the CTS ("blue switch") in the v8. examining the thermostat housing in my 300E, i see that there are two other sensors, one alongside the "blue switch" and another one on the side of the housing. i would think that this "blue switch" that turns on a 35 amp circuit would not be used for engine management but i will leave that to the gurus. if the "blue switch" is indeed the same one as on the v8 then the mod ought to work on the 6 as well. i think this is the main premise behind guido's contention that it works on the E series as well as some other platforms that use this same sensor.

what do you say guys?

cheers

ps. Jim i see on your sig that you also have an E, can you check out what i am talking about?

The blue switch does control the high speed fan, but what I have found to be different between the 6/8 is the 8 has a 3 speed fan and the resistance cut in/cut out points are different than the
6 , which is a 2 speed fan.
So the value of the resistor mod is different.
You can use resistors of choice [ I have tried many values ],
but the design of the system is for the aux. fans to be used as an aid under adverse conditions, not to be a continuously running part of the cooling system.
At the same token, I centainly see dropping the high temp cut-in down 5-7 degress a benefit to the running . But to use resistors of such value as to bring the fans on earlier than normal temps [which seems to be what everyone is looking for], is not neccessary . [ remember, the temp specs on your thermo are 'start to open' specs.]
I finally settled on a value that would bring the cut-in at a temp
that was reached when the car was at a few min. idle on a hot day. That seems to take care of any other load /heat conditions.

I would like to thanks Jim F for his assistance and his resistor
expertise. His design with the use of film resistors for heat/ohms
stability is very good.
Also, the low speed fan mod. that was mentioned is the bridging
of the a/c drier high side pessure sw. and that mod is simply a manual one with a cabin switch for the operator. This mod is
low speed fan .

Arthur,

What resistance value did you wind up using and what was the cut-in temperature that it worked at? It appears that you are validating this approach yes? I certainly don't want to "bring the fans on earlier than normal temps" but just want to make sure it doesn't go much farther than that first line above 80 degrees (what the heck is that anyway - 100 deg?). I have watched the needle creep up in traffic in the summer and it went maybe an eighth of the way to 120 before the fans kicked in and cooled it all the way down to 85.

re: Film resistors - I have seen references to thin, thick, metal, carbon film. Which one and what wattage?

On your other point - you are using the low speed circuit as a manual override? Is it effective or is it now redundant in stop and go situations? I myself am in favor of redundant / failsafe mechanisms and have been thinking about adding such a modification.

Cheers

JS
The line you are referring to is 100C.
I wound up using a 1.82k after trying a 1.5 for several weeks.
This gets the fans on at approx. 100C vs the stock 105/107.
I like this as they are called for only when needed. This also gives you a cut-out of about 95C.My car seems to run best in the 90/95 eng temp range.
The parts are available from RS

They have to be ordered , as they are RSU #s. { not normal stock]
1.5k -1% tol., metal film, 1/4 watt---RSU11345766.
1.82k-RSU11345774
5- pack/$.99

If you can't find them, email me and I will sent a few of each to
you.
You may like the 1.5k better, but I found that the cut-out point was too low and had what I considered to be a too long running fan time when not needed.

As far as the man. sw in the cabin- I have done this with Benz for many years and kinda like having that control. Beats putting the heat on......does have it's uses and gives you the jump on the temps..

Great info Arthur and much obliged! I'll put in that manual override too, had good success with that on other cars I've owned...

Cheers

went to RS & ordered one package of each - less than $5 delivered to my house. i asked if they could get me 1.1k ohm and i got a blank look - apparently they only knew to special order with the RSU number. but now my temps don't even go near 100 degs - this may have to wait until warmer weather next year!

>>but now my temps don't even go near 100 degs - this may have to wait until warmer weather next year! <<

That's why I went with the higher resistance. No sense in an aux fan being called for when it's not needed.

Art, you'da man!
 

I just found your post, JS! As usual, Art has done his usual great job. Actually this is the most verbiage that I ever seen from him! :)

I sold my E320 in Feb, so lost a test vehicle. Removed it from my sig.

I've just tested a 300E and a 190E 2.3 with 1.1K and they both came on around 92 - 93C.

You bring up a good point re when to cut in the AUX fan(s). Since I've been experimenting with a small head gasket leak, I lost my nice 40/60% mixture (AF/water) and Water Wetter (WW).

Periodically, I clean the expansion tank (about 4 qts) and refill it. Do this to see how much oil is not accumulating. But my mixture is at least 50/50% plus there's no WW. I can see that in the TEMP gauge. After a 20 mile freeway run, jumping immediately in stop/go traffic, the temp gauge 'bangs' just under the 100C mark. This is with the 1.1K resistor which, after 7 months, is still within a few ohms of its initial value.

With 40/60 and WW, the car would never get above 92C or so. Plus the fans are going in both cases. With a little more water and WW, the aux fans would just cycle a bit. But with the present, the fans are getting a good workout, so does the alternator! :(

Jim,

I too lost all my ww due to the head gasket job I just got through. Now it has 60/40 (over protected) MB coolant. I did not have the ww long enough to observe the overall effect - maybe when it gets warm again. I saw your write-up on this coolant mod on your webpage. Are you gonna include this new info? I think it is a very worthwhile little project!

Cheers

just an update
 

I had gotten the resistors awhile back and even the connectors from JimF. This weekend I got caught in some pretty horrendous NYC traffic jams and my temps went up and over the 100 deg mark and triggered the aux fans. The following morning I cobbled up a 1.8k pigtail from my parts collection and plugged it in. Sure enough I got caught in an even worse jam than the previous one. This time though, my temps would hover just beneath the 100 deg line and never even touched it. It did stay up there though, so I think that it was cutting out at about 95 degs. Temps went back down after the traffic eased up. It only took a half hour to make the first pigtail so I think I'll make me a 1.5k version and see how that behaves. BTW, I used this hi- temp silicon wrap I got at RS to cover the exposed wires as a precaution against engine bay heat.

. . That's why
 

I recommend and use the 1.1K ohm. It keeps the temp around 90C or so. Of course, the fans work harder but that's why they are there.

Give the 1.2K ohm (95C) a try next, and you'll probably like that a little better.

This thread and photos would make a great DIY article, especially the resistor/temp relationship, manual overide wiring, etc!!!

Jim,
I installed the cool harness I got from
you and my car never saw 100c.again.$34.bucks?
very neat, look like oem.and it works.
Thanks Jim,

good feedback . . .
 

JCE: The pics on my page allow you to DIY. But you would be surprised how many people perfer the completed unit.
For DIYer, here's the page link: http://pages.prodigy.net/jforgione/MB_CTS.html

Manny: FYI, he uses the 92C version.

That's why I loved this site so many intelligent people.

JimS500, Jsmith:Where did you put the resistor? on the thermostat housing switch or in the 2 pole blue switch(ct sensor) near the valve cover and air filter housing,I assume you have an M103 engine?.I wanna do this to my 93 190e 2.6(m103) but I'm a little bit confuse on where to solder the resistor.Thanks