Can someone tell me what temperature the fans kick on at. I have an 87 Formula 350 if this helps. Also, what are your normal opperating temps? ANy help would be greatly appreciated

 

Primary comes on at 233, or thereabouts. Secondary comes on at 238, or when a/c head pressure gets high enough. The secondary fan coming on should turn on the primary as well.

 

I tapped into the sensor wire and ran it to a switch(which just gounds it out)...I can turn my fan on and off when I want but it still has that sensor in there....my primary does not come when the secondary does and the secondary does not come on at all by itself....maybe I used too much teflon on there and the sensor can't make ground?

 

228 is the kick-in. If you have a 2 fan setup it might kick in one fan first and the other one later, but nothing happens before 228. Why GM lets the motor get that hot is beyond me, but that's the same temp they've used for YEARS. My 1994 LT-1 Formula also kicks in the fans at 228 (A/C off, of course).

"Normal" operating temp?? Somewhere between your thermostat temp and 228. On the highway you should be down within 10 degrees or so of your stat temp. In traffic it'll work up to 228, fans kick in and back down to about 205, fans go off again, temps work back up.... etc.

 

Damon is correct about GM's typical "on" temperature to turn the fans on. On my SD car, the ECM turned #1 Fan on at 228 and off at 220. #2 is controlled by the temp sensor in the passenger head. The ECM cannot turn on Fan#2 by itself, but it can with Fan#1.

I also agree with Damon that GM turns the fans on too late and then runs for a fairly long time. I have found that reprogramming the ECM to turn on Fan#1 about 10*F above the T-stat's rated temp (i.e. with a 180* T-stat, turn on the fan at 190*) and then turn off when the temp falls to 5* above the rated temp of the T-stat (i.e. 185* for a 180* t-stat). This will keep the engine temp more consistent resulting in more consistent performance between "hot and cold" (as many TPI users have noticed).

One note, you SHOULD monitor your t-stat's actual opening and closing temps with a scan tool if you plan to turn the fans on & off closer to the t-stat's rating. I have found a t-stats can vary by +/- 5* from their rating, so if you actual t-stat was 5* hotter before it opened, you could have a situation where the fans have a lower "off temp" than the minimum temp the stat will operate before it closes and won't get any colder.

 

Where can you get an EPROM that allows you to change the temp the ECM turns the fans on at?

 

Here is what I did after my 406 install, I had the primary fan turn on temp changed to 190* and installed a 180* stat. Replaced the stock secondary fan switch in the passenger side head. To a wells part SW555 (Buick V6 Turbo) turns the second fan on at 208*. The car stays right around 180* or so on the highway to 200/205* in heavy stop and go traffic. I never have to worry about flipping a switch for the second fan to come on.

 

Emissions and fuel mileage, no other reason. I also agree, its way too hot.