i recently installed dual fans instead of single. I have two switches with indicators that tell me when each of the fans is on. I used the plug from the single for the primary fan and just made the secondary manual.

well heres my question. i now know that the primary fan is always on! i am guessing this was some previous owner baloney as the thermostat was missing, etc. anyhow, how do i figure out what has been changed to make this on all the time?

another note is that when i turn the keys to on but do not start the car, the fan is not on, yet i can turn it on from my new manual override switch. this leads me to believe they did not simply ground the relay, or else it would turn on when you only turn the key.

any ideas? how do i trace this? if they put a lower temp switch in would it turn on when i start the car?
or is this normal and i dont know it?

Thanks!

 

i did some driving tonight, and i think i got some more info: my fan is dyslexic!
its on < 180 and off > 180.
wtf. i will try some more tomorrow when its hot outside. i was borderline temps tonight. i could just imagine gettime pulled over for speeding tonight "oh see officer i was trying to heat up my engine"
this could be why she stays cool for a while then stays hot for a while, lol.
how in the world do i fix this?

 

try a new fan switch*in the pass head, between #6 & #8 cyls. it may be bad causing the effects you describe (all I can think of for temp related ), it should also have dark green(?) wire attached to it, if it does, unplug it, then see ifc the fan is on(cold temp), if no, ground the wire and the fan should come on, if it does, replace the switch, I got one for a 87 V6 buick t-type, it comes on at a slightly lower temp(210-215) than the stock one(225-230)

 

but i thought in a single fan setup its controlled via the ECM? remember mine used to be single but i just unplugged the wires and had them go into my new "primary" fan.

check out this post:
https://www.thirdgen.org/techbb2/sho...ght=fan+switch

so is my ECM dyslexic?

 

this is still my setup on the primary fan:
http://www.gmtips.com/3rd-degree/dox/tips/cool/fan.htm

 

any thoughts on the CTS?:
http://www.gmtips.com/3rd-degree/dox/tips/cool/cts.htm

im not too sure this would cause dyslexia though...

 

OK i dont know if im stupid or what, BUT im pretty sure i figured it out. did some more driving. my ECM is not dyslexic.

the fan is controlled by the speedometer, not the temperature.
i've never read about this i guess thats why it threw me for a loop.

on the upward slope it turns off at about 50 MPH.
on the downward slope it turns on at about 30MPH.
the inbetween depends on which direction youre going.

i guess this makes sense since they figure over 50 your getting enough air from the air dam while slow speed you will need the fan for air circulation. silly me!

is there anything wrong with running fans at freeway speeds?

 

my 89 tbi single fan is controlled by a switch in the head