W126 AC / Aux Fan modification

[compu_85]

Just pondering something here, would like input from the membership.

How my 91 350SDL was set up from the factory:

Dual pusher electric fans kick on to low speed with AC high side is over 250 PSI.
Fans kick on to high speed when coolant temp is over 110*C.

Simple mod I have done:
Temp sensor mounted on ABS unit turns the fans onto low speed when the receiver / dryer or engine bay is above ~90*C. It is wired in parallel with the AC high pressure switch.




The fans move a lot more air on high speed. I have an upgraded alternator, and the fans draw 16 amps on high so that won't be a problem.

I'm thinking of either doing:

A) High pressure switch or 110*C coolant temp kicks the fans onto high speed, engine bay / AC temp over 90*C kicks fans onto low.

B) High pressure switch kicks fans onto low. Engine bay / AC temp or coolant temp kick fans onto high.

I'm thinking of going with B, as I really only want the fans blasting away on hot hot days.

Any input?

Thanks,

-Jason

[compu_85]

Nobody has any suggestions?


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[funola]

Originally Posted by compu_85

Nobody has any suggestions?


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Don't do it because it is a hack and will make a mechanic's life difficult and they may refuse to work on it.

[daw_two]

I'm thinking of changing the 87 Champagne condensor out to the dual fan one I pulled from the 91 350SD. Having the dual electric fans out front should be an advantage if I can engineer some way to control them.

Consider:
My current driving includes a lot of stop and go during my morning/afternoon commute to/from work. I'm considering not driving the 300SDL during these daily work commutes. Decisions, Decisions, Decisions. The 87 Champagne might just become my Interstate cruising car and thus not need any modifications. But then again.....if I take it on a trip and once I get there, I have some stop and go driving to do in traffic.....then I will want better AC.

Decisions, Decisions, Decisions......

[compu_85]

Originally Posted by funola

Don't do it because it is a hack and will make a mechanic's life difficult and they may refuse to work on it.

I'd hardly call moving one wire on the relays a hack.


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[funola]

Originally Posted by compu_85

I'd hardly call moving one wire on the relays a hack.


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Not according to Ed Wyatt, a mechanic making a honest living.

[qwerty]

Originally Posted by funola

Not according to Ed Wyatt, a mechanic making a honest living.

Could you give us a telephone number for Ed? I would hate do do something to my car that Ed might not approve of!!!

Don't tell Ed, but I just happen to have one of my door lock actuators bypassed at this very moment.

Originally Posted by funola

Don't do it because it is a hack and will make a mechanic's life difficult and they may refuse to work on it.

Ed would probably go into shock if he encountered something like this:
http://www.peachparts.com/shopforum/diesel-discussion/320878-open-close-windows-without-ign-key-diy.html
Wait!!! Whose idea was that?

[whunter]

Originally Posted by compu_85

Nobody has any suggestions?
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Jumper the refrigerant temperature sensor = lock it in HIGH for the summer.



.

[compu_85]

I could also have the fans come on low whenever the compressor is running, and have them kick onto high when the high pressure switch closes. That wouldn't be too hard to do...

GenII cars have a 250 PSI switch, not a temp switch.

-J

[brandlj]

I have my high temp switch jumped on my 86 300sdl. Yes my fan runs high speed all of the time. Yes it can be a little noisy as I sit in the McDonalds drive thru line. Yes, I might burn out the fan motor by the end of the summer ( it is 26 years old ), but I have 3 extras in the attice. I also have a 2 fan setup in the attic, but have never installed it as this works just fine for me.

[JamesDean]

In my 190E, I removed the aux resistor... I ran power straight from the battery and installed two relays (one for each fan) so that when low speed is demanded the fans kick on at full power. I have a 143 amp alternator and see no reason not to do this.

I also have a manual override switch installed on my knee panel incase temps creep up for some reason.

I would make the modification and run the fans full speed. The only downside is noise.

[ds190]

Originally Posted by compu_85

Nobody has any suggestions?


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I prefer manual control- I connected a wire to the engine temp sensor with a switch in the console. I turn on HIGH speed aux fan when I want too:-)

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[E150GT]

If i were to install an additional electric fan to my 84, how should it be wired in? I know a relay is needed but I have no idea where to wire it?

[Hit Man X]

Originally Posted by E150GT

If i were to install an additional electric fan to my 84, how should it be wired in? I know a relay is needed but I have no idea where to wire it?

Why not upgrade to the '85+ aux fan? It is significantly larger.

[E150GT]

Originally Posted by Hit Man X

Why not upgrade to the '85+ aux fan? It is significantly larger.

Because I already have the extra fan and it covers the condenser quite nicely