What would be the problem with...

[epapp]

wiring the signal wire for the low speed fans to the high speed fans relay?

What I aim to get out of this is quicker cool down from the low speed/temp operation (instead of using the low speed fans to cool down from the low temp fan operation, it would use the high speed fans). I also want to get more cooling ability at the lower temp (so as to keep the car cooler). For example, freeway 85 mph, 90F day up a long hill will cause the low speed fans to turn on (212F) and if I'm really loading it/driving hard, the temp can slowly rise up to 216, when the high speed fans come on.

If I wire the low speed operation to the high speed relay, any fan operation will be able to keep the car cool without it getting to 216 first before the highs normally come on.

Besides it sounding like I'm standing next to a hurricane whenever the car reaches 212, are there any other problems from doing this?

[Timco]

The last time I saw this discussed, I believe the consensus was that it would cause a black hole. Not worth the risk.

[epapp]

Well that's it, I don't think there are any risks. Whether or not it helps anything is another question.

But I've decided as part of a larger integrated car system I'm working on, aggressive temp controlling via automatically controlling the relays will be part of it, with failsafes to the standard ECU fan control of course

[Steve Tinker]

I guess the question is why your temperatures are so high.
The only time my low speed fans come on is if the A/C is switched on or in heavy traffic. I can't say I've ever heard the high speed fans kick in except in really heavy stop / go gridlocks, but I do know they work OK because I can switch them on with my Durametric....
No way should the running temps rise as high as you say causing the fans come on (low or high speed) travelling on the open road @ your specified 85mph if the cooling system is functioning correctly.

[epapp]

Well, for one it is my DD, so every situation possible is presented to the cooling system.

Many days when it is hot and I am powering up a long hill on the freeway, or going over a mountain pass really pushing it, the temps will rise above 212 (low speed) and require high speed (216) at which point the temp goes down back to 201-204 when the low and high speed fans turn off.

Both low speed fans and high speed fans work, and I've tested all relays to be sure they are actually coming on. The rads have just been cleaned by me at the beginning of summer and the waterpump is new, as well as a newly flushed and burped cooling system (same behavior before cooling system flush, in case anyone thinks burping it is the problem).

I know of a few others who experience the same symptoms, so I am under the impression that it is normal, and thats WHY the high speed fans exist (really pushing it, low speed fans won't cut it).

Interesting though, my highspeed fans never come on in regular traffic no matter how hot, or how long I'm sitting there, unless I'm using AC