124 Auxiliary Fan conversion
 

Couple questions. Would converting the single auxiliary fan on my 88 300CE to a dual fan from a later 124 make much of a difference in terms of cooling the engine and the a/c system? Secondly, is there any problem fitting the dual fans into an earlier 124?

Thanks for any help.

You could make the ac aux fan run at the higher speed with a relay.

Where would I find such a relay?

why?
 

Does your tag read Heaven, ass & string? (If I translate the German correctly)

What does it refer to? Is it a saying like something is held together on a wing and a prayer?

John in San Antonio
(who is waiting to see about your conversion to maybe try on the 300E)

Where would the relay be installed and how would it make the fan run faster?
 

Arthur, I believe my '88 260E could use the same treatment, but I don't quite understand how it would work.

Thanks.

If you understand the basic operation of the low fan circuit, the single wire terminal on the R15 pre-resistor is the feed for the low fan [ the resistor is in series w/fan motor and that drops the voltage to accomplish a low fan speed].

So if you take that wire off R15 and use it to trigger a seperate relay [ coil side], you can then use a seperate 12V battery V to run the fan on high speed , thereby by-passing the R15.
So, on he contact side of relay [ 30 and 87] , you grab 12v battey source and bring the other side of relay contacts over to the 2 wire terminal of R15..that takes R15 out of the circuit, giing you a high a/c fan vs the stock low fan. It is still triggersed by the a/c pressure swtch circuit b/c you are using that stock circuit and relay to trigger your higher amp relay [ which is required for the higher current load of a high fan speed]

One can also bridge the high side sw S/32 with a cabin sw to give the operator a manual over-ride of the whole fan system, thereby allowing for manual operation when needed [ like towing, traffic jambs, etc]

This over-ride will not change any stock circuits, it simply over-rides those circuits and when not in use , you are back to normal circuitry..a nice feature.

Heaven ass and twine. It's an old mild expletive. When I was a kid in Germany, I used to hear it from my tradesman family members and relatives frequently, typically when a granite paving stone would not fit in place or a piece of wood split.

Sometimes you can hear it in WWII movies.

Another one of the same ilk was Donner Keil noch ein mal!

Thanks for the detailed explanation!

You're Welcome.

I would also add an in-line fuse on the load side of the added relay...Same amp spec as High fan circuit uses.
I don't have your schematic up at this time for that fuse spec, but I do know the schematic wiring itself from memory..

Well, this is a bit beyond my understanding of the electronics. Where is this resistor?